United States EPA-600 /8-84-Ollb
Environmental Protection
Agency March 1984
<&EPA Research and
Development
FEASIBILITY STUDY FOR ADAPTING
PRESENT COMBUSTION SOURCE
CONTINUOUS MONITORING SYSTEMS
TO HAZARDOUS WASTE INCINERATORS
Volume 2. Review and Estimation of
Incineration Test Conditions
Prepared for
Office of Solid Waste
Prepared by
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the SPECIAL REPORTS series. This series is
reserved for reports which are intended to meet the technical information needs
of specifically targeted user groups. Reports in this series include Problem Orient-
ed Reports, Research Application Reports, and Executive Summary Documents.
Typical of these reports include state-of-the-art analyses, technology assess-
ments, reports on the results of major research and development efforts, design
manuals, and user manuals.
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/8-84-011b
March 1984
FEASIBILITY STUDY FOR ADAPTING PRESENT
COMBUSTION SOURCE CONTINUOUS MONITORING
SYSTEMS TO HAZARDOUS WASTE INCINERATORS
Volume 2. Review and Estimation of Incineration
Test Conditions
by
Robert Mclnnes, Edward Peduto, John Podlenski,
Frank Abell, and Stephen Gronberg
GCA/Technology Division
213 Burlington Road
Bedford. Massachusetts 01730
EPA Contract 68-02-3168, Task 55
EPA Project Officer: Merrill D. Jackson
Industrial Environmental Research Laboratory
Research Triangle Park. North Carolina 27711
Prepared for:
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
The U.S. Environmental Protection Agency is sponsoring research programs
to investigate sampling and analysis methods for hazardous waste
incineration. These investigations are focused upon the adaptation of
existing methods for identifying and quantifying those constituents listed in
40 CFR 261 of the regulations. As part of this program, the adaptability of
existing continuous emission monitors systems (OEMS) to hazardous waste
incineration sources was investigated. Measurement categories of interest
include SC^, 803, NOX, 00, 002, 02, HC1, and organic materials.
This report focuses on commercially available sample conditioning and
measurement systems, and presents the results of this adaptability study in
the form of a guidelines document to be used by agency and industry personnel.
The results of this study indicate that commercially available extractive
continuous monitors can be adapted to incinerators through proper sample
conditioning. Conventional sample conditioning systems that dry and remove
particulate matter from the sample gas should be constructed to withstand HC1
gas concentrations of up to 17 percent v/v and temperatures reaching 1700°C
(3000°F). Presently available continuous monitoring instrumentation provides
the ranges and sensitivities needed to accurately measure concentrations of
the organic and inorganic components of interest.
11
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CONTENTS
Figures iv
Tables v
1. Introduction 1
2. Hazardous Wastes 4
3. Incinerators 15
Liquid Injection 16
Rotary Kiln 17
Fluidized Bed 22
4. Emission Control Devices 27
Venturi Scrubbers 29
Packed Bed Scrubbers 30
Spray Towers 32
5. Operating Conditions 36
Combustion Zone 37
Pre-APC Device Monitoring Location 47
Post-APC Device 54
6. Conclusions 62
References 66
111
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FIGURES
Number Page
1 Equilibrium NOX concentration 10
2 Heat of combustion of chlorinated hydrocarbon 11
3 Vertically-fired liquid injection incinerator schematic ... 18
4 Horizontally-fired liquid injection incinerator schematic . . 19
5 Schematic of rotary kiln facility 20
6 Typical fluidized bed incinerator schematic 22
7 Examples of wet scrubber types 31
8 Relationship between boiler excess air and stack gas concen-
trations of excess oxygen (02) and carbon dioxide (002)
for typical fuel compositions 39
9 Carbon monoxide destruction efficiency 50
IV
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TABLES
Number Page
1 Appendix VIII Hazardous Constituents . 5
2 Hazardous Waste Incineration Summary 14
3 Liquid Injection Incinerator Advantages and Disadvantages . . 21
4 Rotary Kiln Incinerators Advantages and Disadvantages .... 23
5 Fluidized Bed Incineration Advantages and Disadvantages ... 25
6 Typical Hazardous Waste Incinerator Operating Ranges. .... 26
7 Combustion Zone Monitoring Parameters 38
8 Pre-Air Pollution Control Device Monitoring Parameters. ... 48
9 Post-APC Device (Stack) Monitoring Parameters 55
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SECTION 1
INTRODUCTION
Proper disposal of hazardous wastes is one of the key environmental
problems of this decade. The environmental abuse associated with improperly
managed, hazardous waste disposal areas, such as the Love Canal site near
Niagara Falls, has alerted all citizens of the need for closely regulated
disposal facilities. To this end the United States Congress in 1976 passed
Federal Law 94-580, the Resource Conservation and Recovery Act (RCRA).
Regulations promulgated under the authority of this legislation establishes
the framework for a strong federal hazardous waste management program.^
These regulations define those wastes that are hazardous and set standards for
waste generators, transporters and hazardous waste management facilities. In
addition, the hazardous waste regulations set forth applicable physical,
chemical, biological and thermal processes that can be used to treat hazardous
wastes.
Disposal of hazardous wastes is limited to four options: ocean dumping,
deep well injection, landfilling and incineration. These processes were used
to dispose of the estimated 57 million metric tons of hazardous wastes that
were generated by industry in 1980.^ The choice of which method is used
depends on several factors including the amount of waste to be handled, its
composition and heat content, the availability of suitable local disposal
sites and the overall disposal economics.
Incineration is beginning to emerge as an especially attractive disposal
technology for several reasons. These include:
• Toxic components of hazardous wastes can be converted to harmless
compounds or, at least, to less harmful compounds.
• Incineration provides for the ultimate disposal of hazardous wastes
eliminating the possibility of problems resurfacing in the future.
• The volume of hazardous waste is greatly reduced by incineration.
• Heat recovery makes it possible to recover some of the energy
produced by the combustion process.
The U.S. Environmental Protection Agency estimates that in 1979 only 5
percent of the total hazardous waste stream in the United States were
incinerated, yet 60 percent of the total wastes could have been destroyed
using current incinerator technology. 2
1
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The performance of an incinerator used for hazardous waste disposal can,
in part, be monitored and defined by Continuous Emission Monitors (CEMS). By
continuously measuring and recording flue gas parameters such as carbon
dioxide (CC>2), carbon monoxide (CO), and hydrocarbon (HC) concentrations,
and temperature and moisture (1^0) levels, the thermal and combustion
efficiency of the incinerator can be determined. In addition, CEMS can
continuously measure specific pollutant emission rates which will determine
the operating efficiency of installed Air Pollution Control (APC) devices as
well as the compliance status of the incinerator with respect to Federal,
state and local pollutant emission regulations.
The environment in which a hazardous waste GEM operates is unlike that
existent of other combustion systems. The wide variation in the composition
of materials which are classified as hazardous, the unlimited number of
combinations in which these materials may be mixed and burned and the varying
combustion characteristics of the individual wastes result in an incinerator
environment that can change substantially from site to site and from burn to
burn.
This report attempts to define the environment of a hazardous waste
incinerator, specifically that range of conditions in which a GEM must
operate. This environment will be defined by the combustion gas temperature,
pressure, excess air and moisture levels, as well as the concentrations of
four primary atmospheric pollutants; hydrogen chloride (HC1), carbon monoxide
(CO), sulfur dioxide (S02) and nitrogen oxides (NOX). In addition the
concentrations of two important combustion process indicators, carbon dioxide
and oxygen will also be addressed.
Operating conditions will be defined and discussed for three principal
sites within a hazardous waste incineration system; in the combustion chamber
where a CEM may be used in determining combustion efficiency, prior to the APC
device where a CEM can assist in determining control device efficiency and
after the APC device, where the quantification of pollutant control efficiency
in addition to establishing atmospheric discharge rates from the incinerator
is essential.
The operating conditions will be defined for these three monitoring zones
for three principal types of incinerators currently in use for hazardous waste
incineration; liquid injection, rotary kiln and fluidized bed. By defining
operating conditions in a number of incinerators, as well as a number of
monitoring locations, more potential CEM installation sites will be described
and the various conditions to be expected will be more clearly understood.
Perhaps the greatest variable in determining flue gas conditions within a
hazardous waste incinerator is the waste itself. To adequately understand the
extent of this variation, this report will first describe hazardous wastes,
the ranges in elemental composition which are encompassed and the combustion
byproducts that result when pure compounds or a mixture of wastes is burned.
The three types of incinerators will then be described, to present the major
differences and the relative advantages and disadvantages of each. This will
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be followed by a brief description of the common air pollution control devices
which may be installed, singularly or in tandem, to limit pollutant emissions
to the atmosphere. These capsule summaries will further clarify the operating
conditions that exist after the control device. The actual operating
conditions at the three potential monitoring locations will then be described.
Any description of hazardous waste incineration must be prefaced with a
statement on the wide range of descriptions for a "typical" hazardous waste
facility. There is no such operation. Hazardous waste, unlike municipal
waste or sewage sludge is not a uniform, homogeneous product, for which
"ideal" incineration conditions can be set and expected operating parameters
narrowly estimated. In fact the exact incineration characteristics of each of
the hazardous wastes defined by RCRA has yet to be firmly established.-* it
goes without saying that the incineration requirements for a small industrial
concern producing one or two specific hazardous wastes will be drastically
different from the large commercial incineration facility that accepts
virtually any type of waste. The wastes will be different and the flue gas
environment will be different. Rather than attempt to describe all possible
combinations of wastes/incinerators/flue gas compositions, this report will
present the variations in each specific category. It is left to the reader to
understand that each installation must be handled individually, and that the
range of conditions defined at each monitoring location may not always apply
in each situation.
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SECTION 2
HAZARDOUS WASTES
In order to implement Subtitle C of the Resource Conservation and
Recovery Act (RCRA), the Environmental Protection Agency (EPA) has promulgated
a broad range of regulations concerning the management of hazardous waste
materials (40 CFR 260-267).^ Hazardous wastes are defined by these
regulations (40 CFR Part 261, Subpart C) according to the ignitability,
corrosivity, reactivity, and EP toxicity of the waste stream. Each of these
four waste characteristics is more specifically defined in Subpart C and
reference is made to Subpart D of the regulations which lists actual wastes
and waste streams that are considered hazardous. An integral section of
Subpart D is Appendix VIII which lists toxic constituents. The presence of
any of these constituents in a waste stream defines that stream as hazardous
(§261.11). Since the Appendix VIII list of hazardous constituents is not
specific to any industry, it has greater broad based applicability than the
other waste-stream definitions and was therefore selected as the basis for
reviewing the composition and potential flue gas emissions of hazardous waste
materials. This Appendix VIII list is presented in Table 1.
There are 375 separate compounds listed as hazardous constituents in
Appendix VIII. These compounds range from pure metallic elements such as
beryllium, cadmium, chromium and lead, to complex compounds containing up to
six different elements such as cyclophosphamide (07^5012^02?) and
dimethoate (C5H^2N03PS2^* Tne Physical states of the Appendix VIII
compounds, their ability to be incinerated and the combustion products they
generate when exposed to the hot oxidizing environment in an incinerator vary
substantially. The combustion characteristics of chemically complex compounds
are especially difficult to quantify since, upon incineration, they may in
part break down irto a number of other complex substances, depending on the
specific combustion zone atmosphere. While much work has been done on
defining the combustion characteristics of Appendix VIII wastes, there is
still much more to do. For example, only 18 percent of these wastes have a
defined auto ignition temperature,^ a parameter useful in determining a
compound's ability to be incinerated. This study will not attempt to define
the limits of current research in this area. The Appendix VIII compounds will
be examined according to their elemental make-up and what reactions should
occur in an incinerator if the correct combustion conditions (time,
temperature and turbulence) are present and what typical incomplete combustion
byproducts may be formed if an ideal oxidizing atmosphere is not present.
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TABLE 1. APPENDIX VIII HAZARDOUS CONSTITUENTS
Appendix VIII
[Appendix VIII revised by 46 FR 27476,
May 20, 1981; corrected by 46 FR 29708.
June 3. 1981]
Hazardous Constituents
Acetonitnle (Elhanemtrile)
Acetophenone (Ethanone. 1-phenyl)
3-{alpha-Aceton>!benzyli-4-nydroxycoiirnarin
and salts (Warfarin)
Z-Acetylaminofl'.Jorene (Acetamide. N-(9H-
fluoren-2-yl)-)
Acetyl chloride (Ethar.oy! chloride)
l-Acetyl-2-thicurea (Acetamide. N-
(aminolhioxomethyl)-)
Acrclein (2-Propena!)
Acrylamide (2-Propenamide)
Acrylonitrile (2-Propeneni!nle|
Afiatoxins
Aldrir. (1.2.3.4.10.10-Hexach!oro-
1.4.4a,5,8.8r.z[c|acridine (3.4-Benzacridire)
Bcn7(ajanthracene (1.2-Benzanthracene)
Benzene (CyiJohexatriene)
Benzenearsonic acid (Arsonic acid, ph^r1,1-)
Benzene, dichloromethyl- (Benzul chloride)
BeiiipnL'ihiol (Thiophenol)
B^nzidme ([l.l'-Biphenvl]-4.4'diamine)
Beiizo[b]/luoranthene (2,3-
Benzofli;oranthene)
B, r-7.o[jinuorantht;ne (7,8-Ber.zofluorantheTie)
Ec:izo[a!pyrene (3.4-Benzopyrene)
p-Benzoquinone (1.4-Cyc!ohexadienedione)
Benzotrichloride (Benzene, trichloromethyl-)
Benzyl chloride (Benzene, (chloromethyl)-)
Beryllium and compounds. N.O.S.*
Bis(2-chloroethoxy)methane (Ethane, 1.1'-
[methylenebis(oxy)]bis[2-chloro-])
Bis(2-chloroethyl) ether (Ethane, 1,1'-
oxybis[2-ch!oro-I)
N.N-Bis'(2-chloroe!nyl)-2-naphthylamine
(Chlornaphazino)
Bis(2-chloroisopropyl) ether (Propane. 2.2'-
oxybis[2-chloro-]j
Bis(chloromethyl) ether (Methane,
oxybis(chloro-|)
Bis(2-ethylhexyl) phthalate (1.2-
Benr.enedicarboxylic acid, bis(2-
eliiy'.hoxyl) ester)
Bromoacetone (2-Propanone. 1-brorr.o-)
Bromomethiiue (Melhyl bromide)
4-Bromophenyl phenyl ether (Benzene. 1-
bromo-4-phenoxy-)
Brucine (Strychnidin-10-one, 2.3-dimethoxy-)
2-Butanone peroxide (Methyl ethyl ketone.
peroxide)
Butyl benzyl phthalate (1.2-
Ber.zrmedicarboxylic acid, butyl
phenylmethyl ester)
2-sec Butyl-4.6-dinitrophenol (DNBP) (Phenol.
2.4-dinitro-6-(l-methy!propyl)-)
Cadmium and compounds. N.O.S.*
Calcium chromate (Chromic acid, calcium
salt)
C-ilcium cyanide
Carbon disulfide (Carbon bisulfide)
Carbon oxyfluoride (Carbonyi fluoride)
Chloral (Acetaldehyde. tnchloro-)
Chlorambu'.il (Eutanoic acid. 4-(bis(2-
chloroethyljaminojbenzene-)
Chit rdcine t.ilphn and j^amma isomersl [4.7-
Mdhnnoindrin. 1.2.4.5.6.7.a.8-oc!Hchloro-
i.4 7.~,i-!otriihydro-| (alpha and gamma
iM!::'.rrs|
Chi'ir:nitted benzenes. N O.S.'
C!'.lonri4tL'd ethane. N.O.S.'
Chlonnaied fluorocarbons. N.O.S.'
Chlorinated naphthalene, N.O.S.'
Chlorinated phenol. N.O.S.'
Chloroacetaldehyde (Acetaldehyde. chloro-)
Chloroalkyl ethers. N.O S.'
p-Chinronniiine (Benzenamme. 4.ch!{jro-|
ChloriyNenxene (Benzene, cnioro-j
Cb'iireljenzii.ite [Benzeneacetic acid, 4-
chl(jro-alpha-(4-chlurophenyl)-alpha-
hydmxy- elhyl ester)
p-C'hlorn-in-crcsnl (Phenol, 4-chloro-3-methyl)
l-CilUiru-2.J-epoxvpropane (Ovirane. £•
(ei:iuruineth> 11 •]
2-Ch:oroeih\ 1 vmvl ether (Einene. (2-
i.hlnrueiho\v I-)
rMorufuim (Methane, tri. hluro-J
C! ioMi.T.elhdne (Mi-thy! chiornlej
Cliloiomethyl melhvl ether (Me!h.ine.
' The abbreviation N O.S (no! otherwise
sp«.'.;ified) signiHt'S rhose members of the ger.c:aJ
cidss not specifically listed by name in this
appt..ijix.
J Chlcironaphlhdiene (Naphthalene, bela-
chloro-)
^-rhiorophenul (Phennl. o-ch!oro-)
l-!i>-Chiorophenyt|thiourea (Thiourea, {2-
rhlnrophenyll-l
3-Chl[ir(ipropioni'i lie iPrupanenitnle. 3-
chloro-j
Chromium and compounds. N.O.S.'
Chrysene (1.2-Beii7phenanthrene)
Curus red No. 2 (2-Naphthol. l-((2.5-
hc acid] (Phenol, methyl-)
(;rjtun.ildehuii> |2-Butfn,il)
CA, tlophosphamide UH-^.^-2.-
Ov .tzrtphnsphonne |bis(2-
(.nioroethyl(dmino|-tetrahv'dro-. 2-oxide)
D,ii:n;imyr.m (5.12 \.iphthdcenedione, (8S-
cis)-fi-dcetyl-10-((3 .imino-2.3.6-trideoxy)-
iiipha-L-lyxo-hexopyranosyl)ox>] 7.8.9.10-
terr;ihydio-o,8.11-tnh>droxy-l-methoxy-)
ODD (Dichlorodiphenyldichloroelhanej
(Klhane. 1.1-dichloro-2.2-bis(p-
f !ilornphen> l|-|
DUE (Elhylene. 1 .l-dichloro-2.2-bis(4-
rh:.irophcnjl|-|
fin i '[)i,:hlorodiphnn ItrichUjroclhane)
IFllune. 1 l.l-tnchluro-2.2-bis(p-
chloruj hi'n>:|.)
Di il:,ile |S-!2,.)-dii-h!oroallyl)
Jnsdpriipi ithiocarbdmate)
Dih'-n7J.i.hjd( ndme (1 2.5,6-Dtbenzacndir.ej
Uihcn/i.i ijdcndme (1,2.7.8-Dibenzacndine)
Dilienzj,i.h{anthracene (1.2.3,6-
I3i!irnz;mlhr;icene)
7li-')ili;nzii[c.s|c,irba70le (3.4,5.6-
Oiber^c.trbdzole]
DiLit'nzoJd ejpyrcne (1.2.4.5-Dibenzpyrene)
Dilwnznja.hjpv rene 11.2.5,6-Dibenzpyrene)
rM.cnzujj iip\rene 11 2.7,8-Dibenzpyrpne)
1.2-Uibromo-3-chloropropane (Propane, 1.2-
dihromo-.'i-chloro-)
1.2 DibriimDethdne (Elhylene dibromide)
Dibromomethane (Methylene bromide)
Di-n-butyl phthalate (1.2-Benzenedicarboxylic
acid, dibutyl ester}
o-[3if-hlorobenzene (Benzene. 1.2-dichloro-)
m Dichlorobenzene (Benzene. 1.3-dichloro-)
p-Dichlorobenzene (Benzene. 1.4-dichloro-)
Dir.hlorobenzone \'OS.' (Benzene.
dii.hloro-. N O S.')
3 3'-Dichlorobenzidme ([l.l'-Biphcnyl|-4.4'-
diamine. 3.3'-dirhloro-]
1.4-Dichloro-2-butene (2-Butene. 1.4-dichloro-)
Dichiorodifluoromethane (Methane.
dichlorodifluoro-)
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TABLE 1 (continued)
l.l-Dichloroethane (Elhylidene dichloride)
V2-Dichloropthane (Ethylene dichloride)
trans-1.2-Dichlornethene (1.2-
Dichloroethylene)
Dichloroethylene. N.O.S.' (Ethene. dichloro-,
N.O.S.-)
1.1-Dichloroelhyiene (Ethene, 1.1-dichloro-j
Dichloromethane (Melhylene chloride}
2.4-Dichlorophenol (Phenol. 2.4-dichloro-)
2.5-Dichlorophenol (Phenol. 2.6-dichloro-)
2.4-Dichlorophenoxyacetic acid (2.4-D). salts
and esters (Acetic acid. 2.4-
dichlorophenoxy-, salts and esters)
Dichlorophenylarsine (Phenyl dichloroarsine)
Dichloropropane. N.O.S." (Propane, dichloro-.
N.O.S.-)
1,2-Dichloropropane (Propylene dichloride)
Dichloropropanol. N.O.S.' (Propanol.
dichloro-, N.O.S.")
Dichloropropene, N.O.S." (Propene, dichloro-.
N.O.S.-)
1.3-Dichioropropene (1-Propene. 1.3-dichloro-)
Dieldrin |1.2.3.4.10.10-hexachloro-6.7-epcxy-
l,4.4a.5.6.7,8.8a-octa-hydro-endo.exo-
1.4:5.8-Dimethanonaphthalene)
1.2:3.4-Diepoxybutane (2.2'-Bioxirane)
Diethylarsine (Arsine. diethyl-)
N.N-Diethylhydrazine (Hydrazine. 1,2-
dieihyl)
O.O-Diethyl S-methyl ester of
phosphorodithioic arid (Phosphorodithioic
acid, O.O-diethyl S-methyl ester
O.O-Qiethylphosphoric acid. O-p-nitrophenyl
ester (Phosphoric acid, diethyl p-
nitrophenyi ester)
Diethyl phthalate (1.2-Benzenedicarboxylic
acid, diethyl ester)
O.O-Diethyl O-2-pyrazmyl phosphorothioate
(Phosphorothioic acid, O.O-diethyl O-
pvrazinyl ester
Diethylstilbesterol (4.4'-Stilbenediol,
alpha.alpha-diethyl. bisfdinydrogen
phosphate. (E)-|
Ditis'drosafrole (Benzene. 1.2-
m<'thylenedioxy-4-propyl-)
3.4-Dihydroxy-alpha-(methyiamino)melhyl
benzyl alcohol (1.2-3enzenediol. 4-|l-
hydroxy-2-(methylamino)ethy!j-)
Diisopropylfluorophosphate (DFP)
(Phosphorofluoridic acid. bis(l-
methylethyll ester)
Dimethoijte (Phosphorodithioic acid, O.O-
dimethyl S-|2-(melhylamino)-2-oxoethyl]
ester
3,3 -Dimethoxybenzidine (fl.l'-Biphenyll-
4.4'diamine. 3-3'-dimethoxy-)
p-Dimethylamiaoazobenzene (Beixzenamine.
N..\-dimethyM-(phenylazo)-)
7,12-Dimethylbenzlalanlhracene (1.2-
Benzanthracene, 7,12-dimethyl-J
3.3'-Dimethylbenziriine |[l.l'-Biphenyl|-4.4'-
diamine, 3,3'-dimethyi-)
Dimethylcarbamoyl chloride (Carbamoyi
chloride, dimethyl-}
1.1-Dimethylhydrazine (Hydrazine. 1.1-
dimethyl-)
1.2-Dimethylhydrazine (Hydrazine. 1.2-
dimethyl-)
3.3-Dimethyl-l-(methylthio)-2-butanone. O-
j(methylamino) carbonyi|oxime
(Thiofanox)
alpha.alpha-Di.T.ethylphenethylamine
(Ethanamine. l.l-dimethyl-2-phenyl-)
2.4-Dimcthylphenol (Phenol. 2.4-dimethyl-)
Oimmhyl phthalale (1.2-BenzeaedicarboxyUc
acid, dimethyl ester)
Dimethyl sultate (Sulfunc acid, dimethyl
ester}
Dinitrobenzene, N.O.S.' (Benzene. Jmitro-,
N.O.S.-)
4.6-Dinitro-o-cresol and salts (Phenol. 2.4-
dinitro-6-melhyl-, and salts)
2.4-Dmitrophenol (Phenol. 2.4-dinitro-)
2,4-Dmitrotoluene (Benzene, l-methyl-2.4-
dinitro-)
2.6-Dinitrotoluene (Benzene, l-methyl-2.6-
dmitro-)
Di-n-octyl phthalate (1.2-Benzenedicarboxylic
acid, dioctyl ester)
i.4-Dioxane (1.4-Oiethylene oxide)
DiphenvUmme (Benzenamine. N-phenyl-)
1.2-Diphenylhydrazme (Hydrazine, 1,2-
diphenyl-)
Di-n-propy!nitrosamine (N-Nilroso-di-n-
pmpylamine)
Disulfoton (O.O-diethyl S-(2-(ethylthio)ethyl|
phosphorodithioate)
2.4-Dithiobiuret (Thioimidodicarbomc
dinmide)
Endosulfan (5-Norbomene, 2.3-dimethanol.
1.4.5.6,7,7-hexachloro-, cyclic sulfite)
Endrin and metabolites (1.2.3.4,10.10-
hexar.hloro-6.7-epoxy-1.4.4a,5.6.7.8.8a-
octahydro-.cndo.endo-l^'.S.S-
dimethanonaphthalene. and metabolites)
Ethyl carbamate (Urethan) (Carbamic acid.
ethyl ester)
Ethyl cyanide (propanenitrile)
Ethylenebisdithiocarbamic acid, salts and
esters (1.2-Ethanediyibiscarbarnodithioic
acid, salts and esters
Elhyleneimme (Azindme)
Ethylene oxide (Oxirane)
F.thylenethiourea (2-fmidazohdinethioneJ
Ethyl methacrylate (2-Propenoic acid. 2-
melhyl-. ethyl ester)
Ethyl methanesulfonate (Methanesulfonic
acid, ethyl ester)
Fluoranthene (Benzo(i,k|f!uorene)
Fluorine
2 Fluoroacetamide (Acetamide, 2-nuoro-S
Fluoroacetic acid, sodium salt (Acetic acid.
fluoro-. sodium salt)
Formaldehyde (Methviene oxide)
Formic acid (Methanoic acid)
Glyctdy(aldehyde (l-PTopanol-2.3-epoxy)
IIdlomethune. N.O.S.'
f loptdchlor (4." Methano-lH-indene.
1.4,5.6.7^.8-heptachloro-3a.4.7.7a-
tetruhydrc-)
Heptachlor epoxide (alpha, beta, and gamma
isomprs) (4.7-Methano-lH-indene.
1.4.5.6,7,8,8-hepl ichloro-2.3-epoxy-3a.4.7.7.
tetrahydro-. alpha. 1 eta. and gamma
isomers)
Hexachlorobenzene (Benzene, hexachloro-)
Hexachlorobutadiene tl.3-Butadiene,
1.1.2,3.4.4-hexachloro-)
Hexachlorocyclohexane (all isomers)
(Lindane and isomers)
Hexachlorocyclopentadiene (1.3-
CyctopentadienB. 1.2.3,4,5.5-hexachtoro-)
Hexachloroethane (Ethane. 1.1.1.2.2.2-
hexachloro-j
1.2.3.4.10.10-Hexachloro-l,4,4a.5.8.8a-
heKahydri>-1.4.5.8-endo.endo-
dimethanonaphthalene
(Hexachlorohexahydro-endo.endo-
dimethanonaphthalene)
Hexachlorophene (2,2'-Methylenebis(3.4.9-
trichlorophenol))
Hexachloropropene (1-Propene, 1,1.2.3.3.3-
hexachloro-)
Hexaethyl tetraphosphate (Tetraphosphoric
acid, hexaethyl ester)
Hydrazine (Diamine)
Hydrocyanic acid (Hydrogen cyanide)
Hydrofluoric acid (Hydrogen fluoride)
Hydrogen sulfide (Sulfur hydride)
Hydroxydimethylarsine oxide (Cacodyllc
acid)
Indenoll^.^-cdlpyrene (1 10-(1,2-
phenylenejpyrene)
lodomethane (Methyl iodide)
Iron dextran (Ferric dextran)
Isocyanic acid, methyl ester [Methyl
isocyanate)
Isoburyl alcohol (1-Propanol. 2-methyl-'
Isosafrole ,Benzene, 1.2-methylenedioxy-4-
allyl-)
Kepone (Decachlorooctahydro-l,3,4-Methano-
2H-cyclobula(cdlpentalen-2-one)
Lasiocarpine (2-Butenoic acid. 2-methyl-. 7-
((2,3-dihydroxy-2-(l-methoxyethyl)-3-
methyl-l-oxobutoxy)methyl)-2.3.5,7a-
tetrahydro-lH-pyrrolizm-1-y! ester)
Lead and compounds. N.O.S.'
Lead acetate (Acetic acid, lead salt)
Lead phosphate (Phosphoric acid, lead salt)
Lead subacetate (Lead, bisjacetato-
O]tetrahydroxytri-)
Maleic anhydride (2.5-Furandione)
Maleic hydrazide (l,2-Dihydro-3.6-
pyridazinedione)
Maiononitrile (Propanedinitriie)
Melphalan (Alanine. 3-[p-bis(2-
chloroethyl)amino|phenyi-, L-)
Mercury fulminate (Fulminic acid, mercury
gait] '
Mercury and compounds, N.O.S.*
Methacrylomtrile (2-Propenenitrile. 2-methyl-
)
Methanethiol (Thiomethanol)
Methapynlene (Pyridine. 2-((2-
dimethylamino)ethyl|-2-thenylamino-)
Metholmyl (Acetimidic acid. N-
iimethylcarbamoyl)oxy]thio-. methyl ester
Methoxychlor (Ethane. l.l.l-.trichloro-2.2'-
bisJp-methoxyphenyl)-)
2-Methylaziridine (1,2-PropyIenimine)
3-Methylcholanthrene (Benz[j]aceanthrylene.
1.2-dihydro-3-methyl-)
Methyl chlorocarbonate (Carbonochloridic
acid, methyl ester)
4.4'-Methylenebis(2-chloroaniline)
(Benzenamine. 4.4'-melhylenebi9-(2-chloro-)
Methyl etnyl ketone (MEK) (2-Butanone)
Methyl hydrazine (Hydrazine. methyl-)
2-Methyllactonitrile (Propanenitrile. 2-
hydroxy-2-methyl-)
Methyl methacrylale (2-Propenoic acid. 2-
methy[-. methyl ester'
Methyl methanesultonate (Methanesulfonic
acid, methyl ester)
2-Me(hyl-2-(methyl!hioipropionaldehyde-o-
(methylcarbonyl) oxime (Propanal. 2-
methyl-2-(methyIthio)-. O-
[(methylamino)carbonyl|oxime)
-------
TABLE 1 (continued)
N-Me.thyl-N'-nitro-N-nitrosoguanidine
(Cuanidine, N-nitroso-N-methyl-N'-nitro-J
Methyl parathion (O.O-dimethyl O-(4-
nitrophenyi) phoaphorothioate)
Methylthiouracil (4-lH-Pyrimidinone. 2.3-
dihydro-6-methyl-2-thioxo-)
Mustard gas (Suifide. bis(2-chloroethyl)-)
Naphthalene
1.4-Naphthoquinone (1.4-Naphthalenedione)
V^Naphthylamine (alpha-Naph.thylamme)
2-Naphthylamine (beta-Naphlhylamine)
l-Naphthyl-2-thiourea (Thiourea. 1-
naphthalenyl-)
Nickel and compounds, N.O.S.'
Nickel carbonyl (Nickel tetracarbony!)
Nickel cyanide (Nickel (II) cyanide)
Nicotine and salts (Pyridine. (S)-3-(l-methyl-
2-pyrrolidinyl)-, and salts)
Nitric oxide (Nitrogen (II) oxide)
p-Nitroaniline (Benzenamine. 4-nitro-)
Nitrobenzine (Benzene, nitro-)
Nitrogen dioxide (Nitrogen (!V) oxide)
Nitrogen mustard and hydrochlohde salt
(Ethanamine. 2-chloro-, N-(2-c!iloroethyl)-
N-methyl-. and hydrochlonde salt)
Nitrogen mustard N-Oxide and hydrochloride
salt (Ethanamine, 2-chloro-. N-(2-
chloroethyl)-N-methyl-. and hydrochloride
salt)
Nitroglycerine (1,2.3-Propanetriol, tnnitrate)
4-Nitrophenol (Phenol. 4-nilro-)
4-Nitroquinoline-l-o\ide (Quinoline. 4-nitro-l-
oxide-)
Nitrosamine. N.O.S.*
N-Nitrosodi-n-butylamme (1-Butanamine. N-
butyl-N-nitroso-]
N-Nitrosodiethanolamine (Ethanol. 2.2'-
(nitrosoimino)bis-)
N-Nitrosodiethylamine (Ethanamine. N-ethyl-
N-nitroso-)
N-Nitrosodimethylamine
(Dirnethylnitrosamme)
N-Nitroso-N-ethylurea (Carbamide. N-ethyl-
N-nitroso-)
N-Nitrosomethylethylamine (Ethanamine. N-
methyl-N'-nitroso-)
N-Nitroso-N-methylurea (Carbamide. N-
methyl-N-nitroso-J
N-Nitroso-N-methylurethane (Carbumic acid,
methylnitroso-. ethyl ester)
N-Nitrosomethylvinylamine (Ethenamme. N-
methyl-N'-nitroso-)
N-NitrosomorphoIine (Morpholine, N-nitroso-
)
N-Nitrosonornicotine (Nornicotine, N-
nitroso-)
N-Nitrosopiperidine (Pyridine. hexahydro-. N-
nitroso-)
Nitrosopyrrolidine (Pyrrole, tetrahydro-. N-
nitroso-)
N-Nitrososarcosine (Sarcosme, N-nitroso-)
5-Nitro-o-toluidine (Benzenamine. 2-methyl-5-
nitro-J
Octamethylpyrophosphoramide
(Diphosphoramide. octamethyl-)
Osmium tetroxide (Osmium (VKIJ oxide)
7-Oxabicyclo[2.2.1]heptane-2.3-dicarboxyiic
acid (Endothal)
Paraldehyde (1.3.5-Trioxane. 2.4.6-trimethyl-)
Parathion (Phosphorothioic acid. O.O-diethyl
O-(p-nitrophenyl) ester
Pentachlorobenzene (Benzene, pentachloro-)
Pentachloroethane (Ethane, pentachloro-)
Pentachloronitrobenzene (PCNB) (Benzene.
pentachloronitro-)
Pentachlorophenol (Phenol, pentachloro-)
Phenacetin (Acetamide. N-(4-ethoxyphenyl)-)
Phenol (Benzene, hydroxy-)
Phenylenediamine (Benzenediamine)
Phenylmercury acetate (Mercury.
acetatophenyl-)
N-Phenylthiourea (Thiourea, phenyl-)
Phosgene (Carbonyl chloride)
Phosphine (Hydrogen phosphide)
Phosphorodithioic acid. O.O-diethyl S-
|(eihylthio)methyl| ester (Phorate)
Phosphorothioic acid, O.O-dimethyl O-[p-
((dimethylamino)sulfonyl)phenyl| ester
(Famphur)
Phthalic acid esters. N.O.S.' (Benzene. 1.2-
dicarboxylic acid, esters. N.O.S.' I
Phthalic anhydride (1.2-Benzenedicarboxyhc
acid anhydride)
2-Picoline (Pyridine. 2-methyl-)
Polychlonnaled biphenyl. N.O.S.'
Potassium cyanide
Potassium silver cyanide (Argentate(l-).
dicyano-. potassium)
Pronamide (3.5-Dichloro-N-(l.l-dimethyl-2-
propynyl)benzamide)
1.3-Propane sullone (1.2-Oxdlhiolane. 2.2-
dioxide)
n-Propylamine (t-Propanamine)
Propylthiouracil (Undecamethylenediamine.
N.N'-bis(2-chlorobenzyl)-. dihydrochloride)
2-Propyn-l-ol (Propargyl alcohol)
Pyridine
Reserpine (Yohimban-16-carboxylic acid.
ll,17-dimethoxy-18-[(3.4.5-
tnme!hoxybenzoyl)oxy|-. methyl ester)
Resorcinol (1.3-Benzenediol)
Saccharin and salts (1,2-Benzoisothiazolin-3-
onp. 1.1-dioxide. and salts)
SatroleiRcnzene. 1.2-methylonedioxy-4-al!y]-)
Selcnious a(.id (Selenium dioxide)
Selenium and compounds. N O.S."
Selenium sulfide (Sulfur selcnide)
Selenourea (Carbamimiduselenoit: acid)
Silver and compounds. N.O.S.*
Silver cyanide
Sodium cyanide
Streptozotocin (D-Glucopyranose. 2-deo\y-J-
(3-methyl-3-nitrosoureido)-)
Strontium sulfide
Strychnine and salts (Slrychnidm-10-one, and
salts)
1.2.4.5-Tetrachlorotienzene (Benzene, 1.2.4.5-
tetrachioro-)
2.3.7,8-Tetrachiorodibenzo-p-dioxin (TCDD)
(Uibenzo-p-dioxin. 2.3,7.8-teirachloro-)
Tetrachloroethane. N.O.S.' (Ethane.
tetrachloro-. N.O.S.')
1.1.1.2-Tetrachlorethane (Ethane. 1.1.1,2-
tetrachloro-)
1.1.2.2-Telrachlorethane (Ethane. 1.1.2.2-
tetrachloro-j
Tetrachloroethylene (Ethene, 1,1.2.2-
tetrachloro-1
Tetrdchloromethane (Carbon tetrachloride)
2.3.4.6.-Tetrachlorophenol (Phenol. 2.3,4,6-
tetrachloro-)
Tetraethyldithiopyrophosphate
(Dithiopyrophosphoric acid, lelraethyl-
ester)
Te(raeth>l lead (Plumbane. tetraelhyl-)
Tetraethylpyrophosphale (Pyrophosphoric
acide. tetraethyl ester)
Tetranitrumethane (Methane, letranitro-)
Thallium and compounds. N.O.S.'
Thallic oxide (Thallium (III) oxide)
Thallium (I) acetate (Acetic acid, thallium (1)
salt)
Thallium (I) carbonate (Carbonic acid.
dithallium (I) salt)
Thallium (I) chloride
Thallium (I) nilrate (Nitric acid. Ib.illmm (!)
salt)
Thallium selemte
Thallium (I) sulfale (Sulfunc ,iud. thallium (I)
salt)
Thioacetamide {Eth.infMhi.xtmuii-i
Thiosemicarbazide
(MydrazinecarbothiOciniidp)
Thiourea (Carbamide thio-)
Thiuram (Bis(dimethylthiocdrb
-------
This review will serve to highlight the advantages and disadvantages of waste
incineration that must be taken into account before the decision to incinerate
a waste is taken.
Three elements contained in many hazardous wastes are especially
noteworthy since they generate heat when completely oxidized or combusted.
'These elements and their heats of combustion (expressed as Btu per pound of
pure substance) are carbon (14,096 Btu/lb), hydrogen (61,031 Btu/lb) and
sulfur (3,984 Btu/lb).^ Compounds that contain these elements may release
heat upon combustion, although the exact heat release potential of any complex
compound cannot be simply calculated from the composition of the compound due
to the varying strength of the chemical bonds which may require significant
amounts of energy to break. Nonetheless, a prime goal of incineration is to
maximize the heat release by providing for complete combustion of these
substances. Carbon, when completely oxidized, will form carbon dioxide
(C02) and provide for the maximum release of energy. If insufficient oxygen
is available for combustion, then carbon will oxidize to carbon monoxide (CO)
or not oxidize at all and form a particulate emission of carbon particles,
thereby not only creating two atmospheric pollutants, but resulting in less
heat release, as unburned carbon releases no energy and carbon forms CO with a
release of only 3960 Btu/lb, a reduction of 72 percent when compared to the
heat released when C02 is formed. Similarly, if sufficient oxygen is
available, hydrogen will combust to water (1^0) and sulfur to sulfur dioxide
(802)> and to a lesser extent sulfur trioxide (SO^). The amount of sulfur
dioxide and sulfur trioxide produced is directly proportional to the sulfur
content of the waste material. Forty six of the Appendix VIII substances
contain sulfur. This constitutes approximately 12 percent of these
compounds. The sulfur composition of these forty-six compounds ranges from 8
to over 90 percent, so the potential for a high S02 concentration in the
incinerator flue gas exists if a pure stream of a substance such as hydrogen
sulfide (H2S-94%S) is burned.
Incomplete combustion of sulfur compounds will also form intermediate
combustion products such as hydrogen sulfide (t^S). As with carbon, less
heat will be released and atmospheric pollutants will be created. Providing
an ideal combustion environment, where sufficient oxygen is available to
produce only carbon dioxide, water, and sulfur dioxide from the combustion of
carbon, hydrogen and sulfur, is an important aspect of hazardous waste, or for
that matter, any type of incineration. Such an environment will maximize heat
release and minimize unnecessary pollutant formation.
Understanding this basic combustion principle is important since
approximately 90 percent of the Appendix VIII compounds contain carbon, 82
percent contain hydrogen and 12 percent contain sulfur. (Many compounds
contain more than one of these compounds; for example, 298 of the 375 Appendix
VIII hazardous constituents, or 80 percent contain both hydrogen and carbon).
The presence of carbon in a material by definition makes thaf an organic
substance. The complete combustion of a simple Appendix VIII organic waste
material such as toluene (Cjti.Q*) is relatively easy to effect and results
in the formation of carbon dioxide and water plus the release of heat.
-------
However, as the organic molecule becomes larger and additional elements become
attached, complete combustion becomes more difficult and the number of actual
and potential combustion products grows.
The fate of other elements in hazardous wastes is also important in order
to determine the make-up of incinerator combustion gases. Approximately 39
percent of the Appendix VIII wastes contain nitrogen. When combusted, this
nitrogen will either be released in the form of elemental nitrogen, N2, or
will form one of the many oxides of nitrogen primarily nitric oxide (NO) and
nitrogen dioxide (NC^)- It is interesting to note that both NO and N02
are Appendix VIII substances and therefore defined as hazardous for this
report. All nitrogen oxides will be collectively referred to as NOX,
without specific identification of the different oxide forms. The distinction
between NO and N02 is not critical from an emissions viewpoint; however it
is important for designers of air pollution control equipment. Nitrogen oxide
formations will occur from both bound nitrogen contained in the fuel (fuel
NOX) and nitrogen contained in the atmospheric air which is supplied to the
incinerator for waste combustion (thermal NOX)• Research to date on the
formation of fuel NOX has concentrated on conventional fuels such as
residual oil (0.2 to 0.8 percent by weight bound nitrogen) and coal (typically
1 to 2 percent nitrogen).5 This work has demonstrated that fuels with
higher nitrogen contents produce more fuel NOX, although the exact formation
mechanism and the specific increase in fuel NOX that results from a known
increase in fuel nitrogen content is not completely understood at this time.
While the overall contribution of fuel NOX to total NOX may not be
necessarily significant with conventional fuels, it can play an important role
in NOX from hazardous waste incinerators. Certain Appendix VIII wastes
contain large amounts of nitrogen (e.g., hydrazine-H4N2~87.5%N) and if
these compounds form the primary waste feed to an incinerator, substantial
amounts of nitrogen oxide emissions may result. One source estimates that for
chemical waste incineration, roughly 5 to 10 percent of organic bound nitrogen
will form nitrogen oxides,^ although this estimate could not be confirmed.
Special incineration systems have been designed to treat potentially high
NOX wastes. Such systems utilize a reduction furnace immediately after the
primary incineration chamber in order to reduce NOX to elemental nitrogen,
N2-2
The formation mechanisms associated with thermal NOX are more clearly
understood. Thermal NOX emission rates are dependent on factors such as
peak flame temperatures, gas residence time at peak flame temperatures and the
amount of atomic oxygen available at high temperatures.-' These
interrelationships are graphically displayed in Figure 1. Hazardous wastes
play an indirect role in thermal NOX formation. Compounds that are
especially stable require higher incinerator temperatures for complete
destruction. These higher temperatures will then result in the formation of
more NOX, regardless of the composition of the compound being destroyed. To
minimize total NOX formation, a hazardous waste incinerator should therefore
be operated at the lowest possible temperature that is necessary to provide
for complete destruction of the waste material.
-------
1000
800
600
400
200
100
30
60
40
o
z
20
10
TTT
- 4.0
\^" 2.0"
1.0
0? Concentration, %
I
Basis: 75% by vol N; (Wet)
1200
1600
2000
2400
2800
3200
3600
TEMPERATURE. F
Figure 1. Equilibrium NOX concentration.^
Another major subclass of Appendix VIII hazardous wastes are the
halogens, which include chlorine, fluorine, bromine and iodine. The principal
element of concern in this group is chlorine. Chlorine compounds,
specifically chlorinated organics, comprise approximately 28 percent of the
Appendix VIII hazardous constituents. The importance of these compounds is
underscored by the fact that current RCRA Regulations for incinerators (40 CFR
264, Subpart 0) specifically address the burning of chlorinated compounds.
The performance standards for hazardous waste incinerators included in these
regulations requires that "an incinerator burning hazardous waste containing
more than 0.5 percent chlorine must remove 99 percent of the hydrogen chloride
from the exhaust gas."°
The combustion of a waste containing chlorine will result in the
formation of either free chlorine, Cl2> or hydrogen chloride, HC1, depending
on the amount of hydrogen available and a number of other factors. Since
hydrogen chloride and other hydrogen halides are more readily scrubbed from
combustion gases than the halogens themselves, sufficient hydrogen should be
provided for this equilibrium conversion to take place. If the waste itself
contains insufficient hydrogen, auxilliary fuel or steam injection is needed
to supply the necessary hydrogen equivalents. The stoichiometric (absolute
minimum) requirements are 1 Ib H£ per 35.5 Ib Cl2 and 1 Ib H2 per 19 Ib
F2 in the waste.^
Due to this hydrogen requirement, the chlorine content of a hazardous
waste stream is closely monitored, and chlorinated wastes will be blended with
nonchlorinated substances to maintain the desired chlorine and hydrogen ratios.
10
-------
Another reason why hazardous waste streams, especially chlorinated
wastes, are blended "concerns the heating value of the waste mixture. The
heating value of a waste corresponds to the quantity of heat released when the
waste is burned, commonly expressed in Btu/lb. Just as carbon, hydrogen, and
sulfur in the pure form release heat upon combustion, so do organic wastes
have some finite heating value. To maintain combustion, the amount of heat
released by the burning waste must be sufficient to heat incoming waste to its
ignition temperature and to provide the energy necessary for the combustion
reactions to occur. One goal in hazardous waste incineration is to blend
wastes so that their combustion is self-sustaining and no auxilliary fuel is
required, thereby minimizing operating costs. While sustained combustion is
possible with heating values as low as 4000 Btu/lb (2222 calories/gram), the
generally accepted minimal heating value that is required to sustain
combustion without the use of auxilliary fuel is 8000 Btu/lb (4444
calories/gram).'» ^
The heating value of an organic waste will decrease if the moisture
and/or chlorine (or other halogen) content increases. Water has no heating
value and, in fact, withdraws heat from the system as it is vaporized and
heated up to the incinerator temperature. Chlorine also has no heating value
and the greater the percentage of chlorine in a waste, the lower will be its
heating content, although there is no simple mathematical relationship.
Figure 2 shows an empirical relationship between heating value and chlorine
content for pure substances. It is common practice in hazardous waste
incineration to blend wastes so that the chlorine content does not exceed 30
percent. This is done to maintain sufficient heating value for sustained
combustion and to limit free chlorine concentration in the combustion
EXPERIENCED RESULTS
1 ,000
60 70 80
1800
CHLORINE CONTENT
Figure 2. Heat of combustion of chlorinated hydrocarbon.
11
-------
Phosphorous ia another inorganic hazardous waste constituent that
requires special considerations. There are 22 Appendix VIII compounds
containing this element, and these compounds comprise approximately 6 percent
of all hazardous waste constituents. Phosphorous will be oxidized in an
incinerator environment to form phosphorous pentoxide, ?2®5' ^ 8a3 when
formed, P2^5 upon cooling forms a phosphoric acid mist with a particle
size in the submicron range." This particulate requires a high efficiency
air pollution control device for particulate control or a two stage scrubber
in which dilute phosphoric acid is used for particulate control in the first
stage and some form of acid gas scrubber is used for the second stage.^ in
either case, the cost of emission control equipment can add significantly to
the overall incineration system expenditure.
The formation of metallic salts, specifically alkali metal salts, during
hazardous waste incineration can cause substantial operating problems by
adhering to the internal surfaces of the incineration system. Alkali metal
salts, which are the salts of sodium and potassium, will attack the refractory
lining of an incinerator.6,12 Refractory constituents such as chromium,
alumina, silicate and magnesia react with the alkali salt to cause spalling of
the refractory, which in turn leads to a significant maintenance problem. In
addition, a mixture of alkali metal salts can form a eutectic compound that
has a lower melting point than either constituent. This can cause significant
operating problems, as the eutectic may condense on internal incinerator
surfaces causing plugging and fouling." For these reasons, alkali metal
compounds are typically segregated from other hazardous wastes and not
incinerated. One example of this policy is an industrial source which will
not feed residues containing more than 50 ppm sodium or other alkali metals to
its hazardous waste incinerator in order to protect the refractory.^
The elemental form of eleven metals as well as compounds containing an
additional five metals are among the compounds listed in Appendix VIII.
Metals have no heating value and when added to an incineration cause a net
heat drain since they must be heated to the incineration temperature. In
addition, when exposed to the high temperature oxidizing environment of an
incinerator, metals will form metallic oxides, which have a small mean
particle size, typically less than 5 microns. These fine particles are
difficult and costly to clean from the flue gas stream. These factors favor
removal of the metal constituents from a hazardous waste stream before
incineration.
One additional factor, beyond chemical composition and heat content, that
may affect whether an Appendix VIII compound is likely to be incinerated or
not is the potential byproducts that may result from incomplete combustion of
the compound. Ideally, a hazardous waste incinerator will provide for
complete combustion of all materials, producing just C02> ^0, S02>
NOX, and some trace amounts of metallic and/or inorganic oxides, depending
on the feed composition. However, improper operation and/or design of an
incinerator may lead to the emissions of products of incomplete combustion
(PIC's). PICs include carbon monoxide, hydrocarbons, aldehydes, ketones,
amines, organic acids, polycyclic organic matter (POM) and any other compounds
12
-------
which escape thermal destruction.10 PICs can pose a serious environmental
hazard in those cases where the original Appendix VIII substance decomposes to
a yet more toxic byproduct. Polychlorinated biphenyls (PCBs) can, under
certain conditions, form polychlorinated-dibenzo-p-dioxins (PCDD), an
extremely lethal substance. Similarly the hazardous material
hexachlorocyclopentadiene (HCCPD) is known to decompose into the even more
hazardous compound, hexachlorobenzene. The potential for generating such
toxic byproducts may play a part in the decision to incinerate a compound, and
such potential points out the need for proper design, operation and
maintenance of any hazardous waste incineration facility.
In summary, the flue gas composition of a hazardous waste incinerator is
largely dependent upon the composition of the waste feed material.
Approximately 90 percent of the hazardous waste constituents listed in
Appendix VIII are organic, and if properly combusted, will oxidize to
primarily carbon dioxide and water. Sulfur oxides will be formed in
proportion to the weight of sulfur in the feed material and nitrogen oxide
concentrations in the flue gas are dependent upon both feed material
composition (fuel NOX) and incinerator operating temperature (thermal
NOX). Chlorinated compounds, when incinerated, form both free chlorine and
hydrogen chloride, with the latter predominating when excess hydrogen is
provided. The same holds true for the other halogens. The incineration of
certain materials including metals and inorganics is avoided, when possible,
due to air pollution considerations, while the alkali metals will cause
operating and maintenance problems inside the incinerator if present in
excessive levels. Finally, certain complex hazardous wastes may form
extremely toxic byproducts if not completely combusted, so optimization of
incinerator design and operation is important.
The heating value of a waste stream is a prime concern in determining
whether incineration is an economically viable disposal option. Hazardous
wastes are blended so that combustion is as self-supporting as possible, and
auxiliary fuel requirements are kept to a minimum. Blending of waste streams
is also used to minimize the concentrations of materials which are difficult
to incinerate, such as inorganics and metals.
There are additional waste related factors that will affect incineration
and that have not been addressed here. The generation rate of each waste
stream that must be incinerated, its physical state (gas, liquid or solid) and
the incinerator operating temperature that is required to ensure complete
destruction, will be a key consideration for determining whether an
incinerator is used and what type of incinerator will be most effective. The
options that are available in this regard will be more fully addressed in the
next section. The affect that waste composition has on the decision to
incinerate is summarized in Table 2.
13
-------
TABLE 2. HAZARDOUS WASTE INCINERATION SUMMARY2
Incineration
Waste containing category
• Compounds containing metals poor
• Inorganic compounds poor
• Unknown percent of chlorine potential
• Carbon, hydrogen and/or oxygen, <30% by potential
weight chlorine, phosphorus, sulfur,
bromine, iodine, or nitrogen
• Carbon, hydrogen, <_30% by weight chlorine good
and/or oxygen
• Carbon, hydrogen, and/or oxygen good
14
-------
SECTION 3
INCINERATORS
The type of incinerator used to dispose of a hazardous waste material
will have an influence on the environment to which a continuous emission
monitor is exposed. Incinerators operate at different temperatures, pressures
and excess air levels and these factors will affect the relative concentrations
of flue gas constituents. While a variety of incinerator designs have been
used to dispose of hazardous wastes, this discussion will be limited to three
principal types currently used by the industry: liquid injection, rotary
kiln, and fluidized bed. These units are widely used due to the advantages
each type offers. While other, less common incinerator types such as molten
salt, pyrolytic and wet air oxidation units have been successfully employed to
destroy certain hazardous waste streams, the number of these novel incinerators
that are currently in use does not warrant an in-depth process description
here. This section will first review the applicable federal incinerator
regulations. At a minimum, incineration systems must be designed to meet
these standards. The three principal incinerator types will then be discussed
with emphasis on how they work, basic system components, and advantages and
disadvantages of each.
The Environmental Protection Agency has promulgated regulations under the
Resource Conservation and Recovery Act (RCRA) that specifically addresses
hazardous waste incinerators (40 CFR Part 264, Subpart 0). These regulations
require that any incinerator used to destroy hazardous waste must:**
• Achieve a destruction and removal efficiency (DRE) of 99.99 percent
for each principal organic hazardous constituent (POHC) designated
in the incinerator's permit.
• Remove 99 percent of the hydrogen chloride from the exhaust gas if
the hazardous waste feed contains more than 0.5 percent chlorine by
weight.
• Not emit particulate matter exceeding 180 milligrams per dry
standard cubic meter (0.08 grains per dry standard cubic foot) when
corrected for 12 percent C02-
The principal organic hazardous constituents that are monitored to determine
the incinerator's destruction and removal efficiency are selected from the
Appendix VIII hazardous constituents list and are established by the EPA
15
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regional office and the incinerator owner/operator based on the type and
concentration of wastes that will be burned. Compliance with this and the
other incinerator performance requirements is determined by a trial burn for
the unit. In addition, operating requirements are designated in the permit
which specify acceptable operating limits for carbon monoxide levels in the
stack gas, waste and air feed rates, and combustion zone temperatures.
Incinerator requirements have also been set forth in regulations
implementing provisions of the Toxic Substances Control Act (TSCA) for
polychlorinated biphenyls (40 CFR, Part 761, Subpart E, Annex I).15 These
regulations specify that an incinerator used to dispose of PCBs must meet the
following combustion criteria:
• Maintenance of the introduced liquids for a 2 second dwell time at
1200°C (j+ 100°C) and 3 percent excess oxygen in the stack gas; or
• Maintenance of the introduced liquids for a 1 1/2 second dwell time
at 1600°C (+_ 100°C) and 2 percent excess oxygen in the stack gas.
These PCS Annex I incinerator requirements also require the monitoring of
various operating and flue gas composition parameters.
It is important to note that while the RCRA regulations do not specify
combustion temperature/residence time values, the PCB regulations do. This is
attributed to (1) the extremely high thermal and chemical stability of the PCB
compounds which mandates extremely high temperatures to ensure complete
destruction of this molecule while ensuring that no toxic byproducts are
formed and (2) the extreme difficulty implicit in specifying combustion
temperature/residence time values for every Appendix VIII hazardous waste
constituent due to the lack of qualitative data on these combustion
characteristics. The specific incinerator temperatures that are required for
a hazardous waste incinerator are left to the EPA permit writer to decide,
based on the constituents of the waste to be burned, the combustion
characteristics of that waste and the potential for formation of incomplete
combustion products. In addition, the RCRA regulations allow for pollutant
removal efficiency as well as destruction efficiency, so the entire
incineration system, including control devices, must be reviewed in judging
the ability of an installation to destroy and remove Appendix VIII hazardous
wastes constituents.
A detailed, step by step review of factors that must be considered in
granting a hazardous waste incinerator permit is presented elsewhere in the
literature.^ This overview of the principal hazardous waste incinerator
designs is intended as a brief summary of the principal operating
characteristics so as to familiarize the reader with the major system
components.
LIQUID INJECTION
Liquid injection incinerators are currently the most commonly used type
of incinerator used for hazardous waste disposal.^ A recent survey of the
16
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hazardous waste incinerator industry indicated that approximately 64 percent
of all hazardous waste incinerators sold were liquid injection units. •1-°
This type of incinerator is made in numerous configurations, but they are
generally classified as vertical or horizontal units. Figure 3 presents the
details of a vertically fired unit while Figure 4 is a schematic of an entire
horizontally fired liquid injection incinerator system. The vertically
aligned liquid injection units are preferred when wastes are high in inorganic
salts and ash contents, while horizontal units may be used with low ash
wastes.10 xhe liquid injection incinerator is probably the most flexible
and labor free type of incinerator due to its compact construction and lack of
moving parts. As the name implies, the liquid injection incinerator is
confined to waste feeds which exhibit a viscosity less than 10,000 SSU, which
is generally the maximum allowed for pumping.^ some wastes are solids at
room temperature but melt when heated, are pumpable and have viscosities that
allow atomization in the liquid waste burner. Effective use of this, or any
other combustion device, requires that the waste be relatively homogeneous
with a relatively constant heating value. Liquid waste incinerators find
applications ranging from complete combustion of non-combustibles such as
contaminated water, to combustion of totally organic compounds, such as waste
solvents.1'
Complete combustion of a waste occurs in a liquid injection unit only if
the waste is adequately atomized and mixed with the oxygen source.
Atomization is usually achieved either mechanically using rotary cup or
pressure atomization systems, or via gas fluid nozzles using high pressure air
or steam. The combustion chamber is a refractory lined cylinder, with
atomized waste fed in at one end and exhaust gases exiting the other. To
ensure a reasonably steady and homogeneous waste flow, liquid injection
incineration systems are equipped with waste storage and blending tanks, as is
shown in Figure 4.
Typical combustion chamber residence times for these units ranges from
0.5 to 2.0 seconds. The operating temperature will range from 650 to 1750°C
(1200 to 3180°F), depending on the destruction requirements of the waste being
incinerated.
Table 3 summarizes the relative advantages and disadvantages of liquid
injection incinerators.
ROTARY KILN
Rotary kiln incinerators are popular for hazardous waste incineration
facilities due to their ability to handle both liquid and solid waste
streams. This versatility is a prerequisite for units installed at commercial
hazardous waste processing facilities, or at large manufacturing complexes
that generate a wide variety of hazardous wastes. They are especially
effective when the size or nature of the waste precludes the use of other
types of incineration equipment. Specifically, waste material such as glass
bottles, cardboard boxes, discarded packing cases, paper and other
unmanageable wastes are often co-incinerated in rotary kilns.1? Figure 5
presents a schematic of a rotary kiln incinerator facility.
17
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EFFLUENT DIRECTLY TO ATMOSPHERE
OR TO SCRUBBERS AND STACK FRESH AIR INTAKE
/ FOR TURBO-8LOWER
FREE STANDING
INTERLOCKING REFRACTORY
MODULES
TEMPERATURE MEASURING
INSTRUMENTS
TURSO-BLOWER
IGNITION CHAMBER
HIGH VELOCITY
AIR SUPPLY
AIR-WASTE ENTRAPMENT
COMPARTMENT
WASTE UNF
AND AFTERBURNER FAN
AIR CONE
UPPER NACELLE
DECOMPOSITION CHAMBER
DECOMPOSITION STREAM
AFTER-BURNER FAN
FLAMES ENS ITIZER
URSUHNCE COMPARTMENT
LOWER NACELLI
AUXILIARY FUEL LINE
ELECTRICAL POWER LINE
Figure 3. Vertically-fired liquid injection incinerator schematic
. 2
18
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20
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TABLE 3. LIQUID INJECTION INCINERATOR ADVANTAGES AND DISADVANTAGES2
Advantages
1. Capable of incinerating a wide range of liquid hazardous wastes.
2. No continuous ash removal system is required other than for air pollution
control.
3. Capable of a fairly high turndown ratio.
4. Fast temperature response to changes in the waste fuel flowrate.
5. Virtually no moving parts.
6. Low maintenance costs.
Disadvantages
1. Only wastes which can be atomized through a burner nozzle can be
incinerated.
2. Heat content of waste burned must maintain adequate ignition and
incineration temperatures or a supplemental fuel must be provided.
3. Burners susceptible to pluggage (burners are designed to accept a certain
particle size; therefore, particle size is a critical parameter for
successful operation).
4. Burner may or may not be able to accept a material which dries and cakes
as it passes through the nozzles.
Rotary kiln incinerators are cylindrical, refractory lined shells that
are mounted with the axis at a slight incline from the horizontal. This
incline, coupled with rotation of the kiln enables solid waste feed material
to gradually pass through the unit by gravity and promotes turbulence, waste
feed agitation and thorough mixing of the waste with combustion air for
maximum waste destruction. It is sometimes necessary to install a secondary
high temperature combustion chamber to complete the destruction of vapor phase
and particulate matter. This secondary chamber can also be used, without the
kiln, if the waste feed material is a flammable liquid. Rotary kilns come in
two basic designs: co-current and countercurrent. Co-current units have the
auxiliary fuel burner at the front (top) end of the incinerator, at the same
end as the waste feed. Countercurrent units have the fuel feed at the lower
end of the incinerator, and combustion gases run countercurrent to the flow of
waste through the incinerator. Both types will destroy a waste, however, for
a waste having low heating value (such as a high water content sludge), the
countercurrent design offers the advantage of controlling temperature at both
ends which minimizes problems such as overheating the refractory lining.2
Residence times within the rotary kiln vary from a few seconds for a highly
combustible gas to a few hours for a low combustible solid waste. Incinerator
temperatures can be varied from 800 to 1600°C (1470 to 2900°F) depending on
the requirements of the waste. Solid wastes, sometimes packed in fiber drums
are generally fed to the kiln by conveyor. Liquids and sludges are pumped in,
with liquids usually strained, then atomized with steam or air.
21
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Table 4 presents a comprehensive list of the relative advantages and
disadvantages of rotary kiln incineration. Due to its ability to handle
solid, liquid and gaseous wastes, the rotary kiln was the preferred
incineration technique for the first two approved commercial hazardous waste
incineration facilities operated by Rollins Environmental Systems at Deer
Park, Texas and Energy Systems Company at El Dorado, Arkansas. Both units
have successfully Incinerated obsolete or excess chemical warfare agents and
PCB compounds, with PCS destruction efficiencies exceeding 99.99 percent. *•*
FLUIDIZED BED
Fluidized bed incinerators are refractory lined cylindrical vessels that
contain a bed of inert, granular material, usually sand. Figure 6 presents a
typical fluidized bed schematic. The bed temperature is limited by the
softening point of the bed medium, which for sand is about 1100°C (2000°F).
Typical fluidized bed incinerator temperatures are in the 450 to 980°C (840 to
1800°F) range. Fluidized air is passed through a distributor plate at a
rate sufficiently high to cause the particles in the bed to act as a
theoretical fluid. Passage of the waste gases through the bed causes
additional agitation and ensures intimate mixing of all waste material with
the combustion air. Hazardous waste materials, including waste gases,
liquids, slurries and sludges are typically injected into or just above the
bed. Normally, bed design restricts combustion to the immediate area of the
bed. This maintains the "freeboard" area above the bed for separating of the
inert particles from the rising gases and for minor combustion of
devolatilized components.
FL'J: CAS
SAND
ACCESS DOOR
AUXILIARY BURNER
/ (OIL OR GAS!
— WASTE INJECTION
^ FUJIDIZING AIR
ASH REMOVAL
Figure 6. Typical fluidized bed incinerator schematic.
22
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TABLE 4. ROTARY KILN INCINERATORS ADVANTAGES AND DISADVANTAGES2
Advantages
1. Will incinerate a wide variety of liquid and solid hazardous wastes.
2. Will incinerate materials passing through a melt phase.
3. Capable of receiving liquids and solids independently or in combination.
4. Feed capability for drums and bulk containers.
5. Adaptable to wide variety of feed mechanism designs.
6. Characterized by high turbulence and air exposure of solid wastes.
7. Continuous ash removal which does not interfere with the waste oxidation.
8. No moving parts inside the kiln (except when chains are added).
9. Adaptable for use with a wet gas scrubbing system.
10. The retention or residence time of the nonvolatile component can be
controlled by adjusting the rotational speed.
11. The waste can be fed directly into the kiln without any preparation such
as preheating, mixing, etc.
12. Rotary kilns can be operated at temperatures in excess of 2500°F (1400°C),
making them well suited for the destruction of toxic compounds that are
difficult to thermally degrade.
13. The rotational speed control of the kiln also allows a turndown ratio
(maximum to minimum operating range) of about 50 percent.
Disadvantages
1. High capital cost for installation.
2. Operating care necessary to prevent refractory damage; thermal shock is a
particularly damaging event.
3. Airborne particles may be carried out of kiln before complete combustion.
4. Spherical or cylindrical items may roll through kiln before complete
combustion.
5. The rotary kiln frequently requires additional makeup air due to air
leakage via the kiln end seals.
6. Drying or ignition grates, if used prior to the rotary kiln, can cause
problems with melt plugging of grates and grate mechanisms.
7. High particulate loadings.
8. Relatively low thermal efficiency.
9. Problems in maintaining seals at either end of the kiln are a significant
operating difficulty.
10. Drying of aqueous sludge wastes or melting of some solid wastes can .result
in clinker or ring formation on refractory walls.
23
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The bed is preheated to start up temperature by a burner located above
and impinging on the bed. The large mass (relative to the mass of waste) and
high heat content of a bed very rapidly raises the waste to combustion
temperatures, which in turn transfers heat to the bed. The residence time of
waste material in the bed typically is on the order of 12 to 14 seconds for a
liquid hazardous waste.
Fluidized bed incinerators are subject to problems caused by low ash
fusion temperatures. This can be avoided by keeping operating temperatures
below the ash fusion level or by adding chemicals that raise the fusion
temperature of the ash to an acceptable level.^
Table 5 presents a list of the relative advantages and disadvantages of
fluidized bed incineration.
While there are only a few fluidized bed units now in operation, this
number is expected to increase due to the versatility of this device. The bed
material can be altered to meet the specific disposal needs of the incinerator
operator. For example, limestone may be used as a bed material when
organophosphates are incinerated. In this application the limestone acts as a
scrubber to capture phosphates from the process creating a nontoxic solid
residue rather than a sludge that would result from external scrubbing
devices.^0 Similarly, a catalytic bed media can be utilized in the case of
an unusually difficult to destruct waste. Sand has been successfully used as
the bed media in the incineration of chlorinated and flammable compounds with
a total halogen content of fuel in excess of 27 percent.**• In this
application, destruction and removal efficiencies of principal organic
hazardous constituent exceeded the required 99.99 percent.
The typical operating ranges for liquid injection, rotary kiln, and
fluidized bed incinerators are summarized in Table 6. The selection of a
specific unit depends on a variety of factors including capital and operating
cost, amount, composition and variability of hazardous waste material and the
combustion temperature/residence time destruction requirements of the wastes
to be incinerated. As is evident from Table 6, rotary kilns and liquid
injection incinerators must be used if the hazardous waste requires high
temperature exposure, while fluidized bed units may be the choice if a longer
residence time at a lower combustion temperature is sufficient to result in a
destruction and removal efficiency in excess of 99.99 percent. Therefore,
continuous emission monitoring equipment that is to be installed in the
combustion zone of a hazardous waste incinerator will be exposed to a more
severe temperature environment if utilized in conjunction with a rotary kiln
or liquid injection unit. Specific flue gas parameters that may be found in
each of the three principal incinerator types will be more fully discussed in
Section 5 of this report.
24
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TABLE 5. FLUIDIZED BED INCINERATION ADVANTAGES AND DISADVANTAGES
Advantages
1. General applicability for the disposal of combustible hazardous solids,
liquids, and gaseous wastes.
2. Simple design concept, requiring no moving parts in the combustion zone.
3. Compact design due to high heating rate per unit volume (100,000 to
200,000 Btu/hr-ft3 (900,000 to 1,800,000 kg/cal/hr-m3) which results
in relatively low capital costs.
4. Relatively low gas temperatures and excess air requirements which tend to
minimize nitrogen oxide formation and contribute to smaller, lower cost
emission control systems.
5. Long incinerator life and low maintenance costs.
6. Large active surface area resulting from fluidizing action enhances the
combustion efficiency.
7. Fluctuation in the feed rate and composition are easily tolerated due to
the large quantities of heat stored in the bed.
8. Provides for rapid drying of high-moisture-content material, and
combustion can take place in the bed.
9. Proper bed material selection suppresses acid gas formation; hence,
reduced emission control requirements.
10. Provides considerable flexibility for shockload of waste; i.e., large
quantities of waste being dumped in the bed at a single time.
Disadvantages
1. Difficult to remove residual materials from the bed.
2. Requires fluid bed preparation and maintenance.
3. Feed selection must avoid bed degradation caused by corrosion or reactions.
4. May require special operating procedures to avoid bed damage.
5. Operating costs are relatively high, particularly power costs.
6. Possible operating difficulties with materials high in moisture content.
7. Formation of eutectics is a serious problem.
8. Hazardous waste incineration practices have not been fully developed.
9. Not well suited for irregular, bulky wastes, tarry solids, or wastes with
a fusible ash content.
25
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TABLE 6. TYPICAL HAZARDOUS WASTE INCINERATOR OPERATING RANGES
Process
Temperature
range °C (°F)
Residence time
Liquid injection
Rotary kiln
Fluidized bed
650
(1200
800
(1470
450
(840
1750
3180)
1600
2900)
980
1800)
0.5-2 seconds
Liquids & gases - seconds
Solids - hours
Liquids & gases - seconds
Solids - hours
26
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SECTION 4
EMISSION CONTROL DEVICES
In addition to the combustion zone, two additional sites that may be used
for the placement of continuous emission monitors are those located
immediately before and after the air pollution control (APC) device.
Monitoring at these locations will typically be conducted to:
• provide a determination of the control device pollutant removal
efficiency, and
• provide a determination of facility compliance with applicable
emission regulations.
As previously stated, the Federal (EPA) emission requirements for a hazardous
waste incinerator include :°
• destruction and removal efficiency of 99.99 percent for each
principal organic hazardous constituent designated in the
inc inerat or ' s p enoi t ,
• removal of 99 percent of the hydrogen chloride from the exhaust gas
if the hazardous waste feed contains more than 0.5 percent chlorine,
and
• a particulate emission limitation of 180 milligrams per dry standard
cubic meter (0.08 grains per dry standard cubic foot) when corrected
for 12 percent
Continuous emission monitoring and stack (post-APC device) testing will be
used to determine compliance with these standards.
Typical operating parameters for the pre-APC and post-APC device
monitoring locations are dependent upon the type of device(s) installed. The
selection of these devices is in turn dependent on the applicable emission
regulations (local, state, and federal), the physical and chemical
characteristics of the hazardous waste stream being incinerated, the types and
amounts of pollutants generated, and the expected pollutant removal efficiency
of the APC devices. This section briefly discussed the principal APC devices
currently in use, their principals of operation, and their advantages and
disadvantages. This data will serve to provide background information for the
typical operating conditions that will be discussed in the next section of
this report.
27
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Air pollution control for the hazardous waste incinerators described in
the previous section can be categorized as being primarily for particulate or
gaseous emission control, although each device will remove some of the other
pollutant stream. The particulate emission control devices favored by the
hazardous waste disposal industry (based on existing installations) can be
limited to afterburners and venturi scrubbers, although select, individual
facilities may utilize electrostatic precipitators or fabric filters.
Inasmuch as afterburners are only used today with rotary kiln incinerators and
the principles of operation of these control devices are similar to liquid
injection incinerators, they need not be discussed in more detail here. The
venturi scrubber, which removes both particulate and gaseous emissions will be
addressed. Gaseous control devices to be reviewed include packed bed towers,
spray towers and plate columns (also known as tray towers). In addition, many
control devices are commonly preceded by a heat recovery or quench section.
Therefore, the purpose and nature of this pre-treatment will be addressed
first.
Flue gases will exit a hazardous waste incinerator at temperatures
ranging from 800 to 1100°C (1470 to 2000°F).9 Before these gases enter an
APC device, some form of gas cooling is practiced in a majority of hazardous
waste incineration facilities. This temperature reduction serves to lower the
volume of gases which must be handled by the APC device, and thereby lowers
the size of the device required. At the same time, the lower gas temperature
allows the use of low temperature materials of construction rather than more
expensive, high temperature alloys or refractory.^
Flue gas cooling is typically practiced in one of two principal ways.
The most common method, according to a recent survey of hazardous waste
incinerator manufacturers^ is heat recovery. This technique utilizes a
waste heat boiler or some similar device to transfer heat in the flue gases to
a second medium, either water or air. This practice recovers valuable energy
that can be utilized elsewhere in the process while simultaneously lowering
the flue gas temperature. The amount of energy recovered is dependent upon
the final flue gas temperature, which in turn is set by the APC device. If an
electrostatic precipitator is used, the outlet temperature from the heat
recovery section is usually maintained at approximately 290 to 310°C (550 to
600°F). If a fabric filter or a wet scrubber is used, then the outlet
temperature may be closer to 150°C (300°F).7
In place of, or at times, in addition to heat recovery, water quenching
is used to lower flue gas temperatures. For these devices, a simple water
spray system is used to adiabatically cool the flue gas 50 to 150°C (120 to
300°F).* if the gas is cooled below 95°C (200°F), acid resistant
construction materials such as fiber reinforced plastic (FRP) must be used to
minimize corrosion.^2 Quenching of the gas stream, especially before a wet
collection device, also serves to minimize the evaporative water losses that
occur in the principal scrubbing device. Without quenching, evaporative water
loss from caustic^or lime solution can lead to particulate emissions of sodium
or calcium salts.^
28
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VENTURI SCRUBBERS
One of the most predominant air pollution control devices for hazardous
waste incinerators is a venturi scrubber, also known as a gas atomized spray
scrubber. This device and other scrubbers are shown schematically in
Figure 7. A typical venturi scrubber contains a section of ductwork with a
converging central section (throat). Liquid is introduced at the throat and
is atomized by the movement of incinerator flue gas through the throat
section. The atomization breaks the liquid into fine droplets which allows a
larger surface area for particulate interception. It is the gas/liquid
contact that permits removal of gaseous contaminants, while it is the
collision of particulates in the flue gas and the water droplets which causes
particulate removal.
Quenching of the gas stream prior to a venturi scrubber is optional, as
the venturi may be used for this purpose. If the gas stream contains acid
gases, such as HC1, SO2 °r NOX, a caustic solution may be used in the
venturi to effect acid gas removal. However, significant amounts of HC1 can
be removed by water alone. For these cases, the interior surface of the
venturi is typically lined with a nonmetallic material such as fiberglass
reinforced plastic (FRP), rubber, carbon graphite, teflon or kynar
(polyvinylidene fluoride).' Venturi scrubbers are usually followed by some
form of mist eliminator to remove coarse water and acid mist droplets from the
effluent air stream. This mist eliminator may be a cyclonic separator or it
may be one of the other gaseous pollutant removal devices which will
subsequently be discussed. The waste stream applicability and relative
advantages and disadvantages of a venturi scrubber can be briefly summarized
as follows.
Applicable Waste Streams
Suitable for particles, and fairly effective in removing noxious gases
that are highly soluble (HC1, HF) or reactive with the scrubber solution
(S02, NOX, HCN).
Advantages
1. Simultaneous gas absorption and particulate removal
2. Suitable for high temperature, high moisture conditions
3. Particulate removal efficiency is high
4. Scaling not usually a problem
Disadvantages
1. Corrosion and erosion problems
2. Dust is collected wet and the wastewater will have to be treated
29
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3. Moderate to high pressure drop; large amount of energy needed
4. Requires downstream mist eliminator
PACKED BED SCRUBBERS
Packed bed scrubbers are used with hazardous waste incinerators because
of their high removal efficiency for gaseous emissions. With proper design,
packed towers can meet or exceed the federal 99 percent removal criteria for
hydrogen chloride. The nature of the design, however, does not allow for high
particulate loadings, and the packed bed can become clogged if inlet
particulate concentrations are high. A venturi scrubber is used for
particulate control in cases where some form of gas stream conditioning prior
to the packed bed is required.
The packed bed scrubber is a vessel filled with randomly oriented packing
material such as saddles or rings, as shown in Figure 7. The scrubbing liquid
is fed to the top of the vessel while the flue gas flows in either cocurrent,
countercurrent, or cross flow direction. As the liquid flows through the bed,
it wets the packing material and thus provides a surface area for particulate
mass transfer with the flue gas. Differences among packed bed scrubbers
include the flow mode, the packing material and the depth of packing. The
flow mode is dependent upon the particular application, while the depth of
packing determines the liquid/gas contact time and hence affects the removal
efficiency. Packing material comes in a variety of shapes and types including
rings, spiral rings and saddles. Packing materials are usually made of
plastic; ceramic or some other acid corrosion resistant material.
Packed scrubbers are most commonly used with liquid injection
incinerators because of the low particulate loading in the exhaust gas. When
used in conjunction with a rotary kiln or fluidized bed incinerator, they are
usually preceded by a venturi scrubber. The applicable waste streams and
relative advantages and disadvantages of packed bed scrubbers are summarized
below.^
Applicable Waste Streams
Most suitable for the removal of noxious gases in streams containing low
or no particulate loading.
Advantages
1. High removal efficiency for gaseous and aerosol pollutants
2. Low to moderate pressure drop
3. Engineering principles controlling the performance of packed bed
scrubbers are well developed and understood
4. Availability of corrosion resistant packings to withstand corrosive
materials
30
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GAS OUT
LIQUID
DOWNCOMER
"*
PLATES
FC =;
GAS If
f=!<0 LIQUID IN
LIQUID OUT
SPRAY TOWER
GAS IN
GAS
<) LIQUID iN
BACKING
ELEMENTS
/ GAS DISTRIBUTOR
Jf AND PACKING
SUPPORT
LIQtJin
LIQUID
VENTURI
O
LIQUID OUT
PACKED BED
GAS-ATOMIZED
(VENTURI) SCRU86ER
Figure 7. Examples of wet scrubber types.9
31
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Disadvantages
1. Low removal efficiency for fine particles
2. Not suitable for high temperature or high dust loading applications
3. Requires downstream mist eliminator
4. Potential scaling and fouling problems
5. Possible damage to the scrubber if scrubber solution pumps fail.
SPRAY TOWERS
Preformed spray towers are scrubbers in which a scrubbing liquid is
atomized by high pressure spray nozzles into small droplets and then directed
into the flue gas stream within a confined chamber. This device is shown
schematically in Figure 7. The waste gas stream usually enters the bottom of
the chamber and flows countercurrent to the scrubbing liquid, although both
cocurrent and cross—current modes have been used. As the scrubbing liquid
becomes smaller, the relative surface area increases and gas absorption is
enhanced. The gas/liquid interface may occur in a single path, or it may be
directed by a series of baffle plates. In addition, the scrubbing liquid may
be either water or a caustic solution to enhance gaseous pollutant capture.
Inertial impaction of solid particles into the water is the principle
particulate collection mechanism. It can be enhanced by operating with a high
relative velocity between the gas and the liquid collection medium; however,
very small particles do not have sufficient mass to enter a droplet. A summary
of the waste streams amenable to spray towers and the relative advantages of
this device follows.^
Applicable Waste Streams
Spray towers are suitable for gas streams with particles and gaseous
pollutants.
Advantages
1. Simultaneous gas absorption and dust removal
2. Suitable for high temperature, high moisture, and high dust loading
applications
3. Simple design
4. Rarely have problems with scaling
Disadvantages
1. High efficiency may require high pump discharge pressures
2. Dust is collected wet
32
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3. Nozzles are susceptible to plugging
4. Requires downstream mist eliminator
5. Structure is large and bulky
6. Lower particulate collection efficiency than a high pressure venturi
7. Lower absorption efficiency than a packed tower
PLATE SCRUBBERS
Plate scrubbers are verticle cylindrical columns with a number of plates
or trays inside as shown in Figure 7. Like all wet scrubbers, they utilize
intimate gas/liquid contact to remove gaseous contaminants. Each plate has
openings in the form of perforations or slots. The scrubbing liquid is
introduced at the top plate and flows across it, then down to the next plate.
A downcomer, located on alternate sides of each successive plate permits the
downward flow of the liquid. The scrubbing liquid exits through an outlet
located at the bottom of the unit. Incinerator gases enter the bottom of the
tower and pass up through the plate openings before exiting at the top. The
gas must have enough velocity to prevent the liquid from flowing through the
holes in the plates. Gas absorption is promoted by the breaking up of the gas
phase into little bubbles which pass through the volume of liquid in each
plate. Plate towers with two sieve trays are often used as an absorber/mist
eliminator in conjunction with a high energy venturi scrubber at many
hazardous waste incineration facilities.^ The applicable waste stream and
relative advantages and disadvantages of these units are presented below.^
Applicable Waste Streams
Most suitable for the removal of noxious gases with low particulate
loading.
Advantages
1. Simultaneous gas absorption and dust removal
2. High removal efficiency for gaseous and aerosol pollutants
3. Low to moderate pressure drop
4. Efficiency increases with multiple plates
5. Handles high liquid rates
Disadvantages
1. Low efficiency for fine particles
2. Not suitable for high temperature or high dust loading applications
33
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3. Requires downstream mist eliminator
4. Limestone scrubbing solution causes scaling
5. Not suitable for foamy scrubbing liquid
The choice of scrubber types for gaseous emission control is principally
determined by the contaminants to be controlled, the degree of emission
reduction required and the particulate loading in the polluted gas stream.
Where particulates are a significant problem, a venturi scrubber is typically
used upstream of one of the other principal gas collection devices. At most
hazardous waste incineration facilities, HC1 is the principal gaseous
contaminant requiring control. Waste streams containing other organic
compounds are generated in much smaller quantities and are sometimes handled
in special dedicated facilities. In addition, scrubbers designed to
control HC1 emissions are generally also effective in reducing other acidic
gaseous contaminants.
Plate towers, packed beds and gas atomized spray scrubbers (such as the
venturi scrubber) are all suitable for the removal of 99 percent of the
halogens from incinerator exhaust gas as well as for the control of ?2°5
and SO2 emissions. Preformed spray scrubbers are not capable of attaining
this high level of control for gaseous contaminants, although these devices
are more effective for particulate control.
The relative advantages and disadvantages of each air pollution control
device result makes the applicability of any device site specific. For
example, plate towers, packed beds and gas atomized spray scrubbers can all be
used to control gaseous emissions from liquid injection incineration. Because
of lower operating costs associated with lower pressure drops, the packed bed
scrubber is the choice at most liquid injection facilities." Packed beds
and plate towers are generally more effective than gas to atomized spray
scrubbers in reducing gaseous emissions, but less effective in controlling
acid mists. In addition, plate towers or packed beds, when used in
conjunction with gas atomized spray scrubbers, serve the dual function of
eliminating the entrainment of liquid droplets while further reducing gaseous
pollutant emission levels.
The comparative differences between the various scrubber types can be
summarized as follows.'
• For incinerator effluent gases containing corrosive contaminants,
the packed bed scrubber is simpler to construct than the plate tower
built of acid to resisting alloy material. Also, the packing
material can be readily changed to handle different kinds of
corrosive fluids.
• The depth of packing in packed beds can also be changed if removal
efficiency is lower than anticipated or if the carrier gas flow rate
or waste streams incinerated change. There is usually no
flexibility in increasing the number of plates in a plate tower.
34
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• Unless operated at very high liquid rates, the pressure drop in
packed bed scrubbers can be considerably lower than in plate towers
designed for the same efficiency.
• For scrubbers less than about 1 to 1.5 meters in diameter,
investment cost for packed beds are usually lower than for plate
towers. When the scale of operation is large, however, plate towers
are considered more economical.
• Plate towers are less susceptible to clogging problems and can be
cleaned of accumulated particles and dusts more easily.
* Serious channeling problems of gas and liquid streams are not
encountered in plate towers.
Based on each hazardous waste incineration facilities' specific waste
feed composition and applicable emission limitations, an air pollution control
system is designed. These systems, while containing different components,
will typically have a particulate control device followed by some form of
liquid scrubber for gaseous emissions. Prior to entering the initial control
device, the flue gas stream is typically cooled to 50 to 150°C (120 to 300°F)
by either direct water quench or some form of heat recovery. Exiting the last
control device, the flue gases are emitted at approximately 70°C (160°F) and
are saturated with water. While these approximations are site specific, they
enable us to generalize continuous emission monitoring test conditions.
35
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SECTION 5
OPERATING CONDITIONS
The specific operating conditions of interest with respect to continuous
emission monitors include the temperature, pressure, moisture content, excess
air level, and carbon dioxide, oxygen, and carbon monoxide concentrations of
the gas stream as well as the concentrations of three principal air
contaminants; sulfur dioxide (802), hydrogen chloride (HC1) and nitrogen
oxides (NOX). A range of values for each of these parameters will be given
for the three incinerator types under review and for the three monitoring
zones of interest. These ranges will be based on engineering evaluations of
the process under consideration and the types and compositions of hazardous
wastes that may be burned in each incinerator. Where possible, published test
data are included to provide actual test measurements as well as a comparison
of how any parameter measurement might vary in a given test. Unfortunately in
certain cases, such as the pre-air pollution control device zone, there are no
published test results and only engineering estimates can be given. In other
cases, such as combustion zone monitoring, the few test results that are
available have been obtained during the incineration of hard-to-incinerate
wastes such as PCBs and herbicide orange. The operating parameters recorded
during these tests may be more severe than, and not necessarily representative
of, typical hazardous waste incineration efforts. Nevertheless, where data
was available, it was reported.
The reported monitoring parameter ranges are intended to provide a
minimum and maximum for expected gas conditions. They should include most,
but not necessarily all conditions that may be experienced in a hazardous
waste burn. Individual incinerator operators may decide to operate at higher
temperatures or at greater excess air rates than here presented to ensure
complete destruction of the waste being incinerated. These situations were
not prejudged in the establishment of a range for each parameter. In like
fashion, the range of pollutant concentrations may be exceeded if a relatively
pure stream of a single pollutant compound; i.e. hydrogen sulfide, is
incinerated. Again it was judged that such an event is unlikely, and
therefore should not be used to define an unreasonably high maximum
concentration. With this background in mind, we can proceed to define
specific hazardous waste incinerator monitoring conditions, starting with the
combustion zone.
36
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COMBUSTION ZONE
Liquid Injection
The combustion zone characteristics of a liquid injection incinerator can
be the most extreme of the three types of incinerators studied. This can be
attributed to the simple design which permits high temperature operation and
their use in destroying a wide variety of hard-to-incinerate chlorinated
organics, including pesticides and PCBs. These compounds require high
temperatures for destruction efficiencies in excess of 99.99%. The specific
operating temperature is set by the hardest to destroy or the most hazardous
waste(s) to be incinerated and, as shown in Table 7, may vary from 650 to
1750°C (1200 to 3180°F). This temperature would be measured within the
combustion zone, but not directly in the flame. Flame temperatures can be
several hundred degrees centigrade higher than other combustion zone flue gas
temperatures.23
The operating pressure within the combustion zone is determined by
whether a forced draft and/or an induced draft fan is used to move combustion
air and flue gases. If only a forced draft fan is utilized, the chamber will
be under a few inches of positive pressure. Negative pressures are
encountered at installations with induced draft fans. According to a recent
survey of hazardous waste incinerator manufacturers, about half the vendors
supply liquid injection units which operate under slight vacuum while the
other half operates at a slight positive pressure.16
Combustion air flow rates for liquid injection incinerators range from 20
to 60 percent in excess of stoichiometric air requirements.2,16 ideally,
incinerator operators attempt to minimize the amount of excess air while
ensuring complete waste destruction as there is a decrease in thermal
efficiency with increased excess air rates. In certain cases, however,
thermal efficiency (and economic) considerations are secondary. In order to
guarantee thorough waste/oxygen mixing while minimizing the potential for
generating incomplete combustion by-products, incinerators may be operated at
higher excess air levels. The incineration of herbicide orange cited in
Table 7 is one such example. Since this chemical can potentially form
extremely toxic dioxins if not completely combusted, it was incinerated with
higher than normal excess air levels in the two liquid injection incinerators
on board the incinerator ship, Vulcanus. This approach appeared successful
since during the test series, no dioxins were detected in the combustion
zone.23
Excess air levels are also directly related to both oxygen and carbon
dioxide concentrations in the combustion gas. If there were no excess air,
and all available oxygen was consumed in waste incineration, then the oxygen
level would be zero and the carbon dioxide level would be a maximum. However,
the introduction of excess air ensures that there will be a measureable amount
of oxygen and that the carbon dioxide concentration of the combustion gas will
be diluted. This inverse relationship between oxygen and carbon dioxide for
various excess air levels is shown in Figure 8 for conventional fuels. The
exact relationship for a hazardous waste is dependent upon the hydrogen,
37
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38
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oxygen, carbon, and sulfur content of the waste, and will be similar to the
fuel curves presented in Figure 8. The range of oxygen concentrations for
liquid injection incinerators is from 4 to 9 percent, while the range for
carbon dioxide is from 8 to 16 percent.
The carbon monoxide levels within the combustion zone are a function of
the .degree of combustion of the waste. Without intimate waste/air mixing,
some of the carbon contained in the waste feed may escape the combustion zone
without being completely oxidized. This condition is more likely if the fuel
is not completely atomized, if the excess air level is too low or if the
turbulence that creates waste/air mixing is insufficient. Based on published
test data, carbon monoxide concentrations do not typically exceed 75 parts per
million (ppm). Yet, data from a series of experimental destruction tests
conducted on a range of pesticides indicates that carbon monoxide
concentrations in the several hundred parts per million range are not uncommon
and that peak values may reach several thousand ppm.25 while this
experimental incinerator was not a liquid injection unit, it was well
designed, as pesticide destruction efficiencies in all tests did exceed 99.99
percent. This appears to indicate that high carbon monoxide levels are
possible and that the specific CO level is somewhat dependent upon where the
samples are taken from in the combustion chamber. Localized zones of
relatively high CO levels may be present in a combustion chamber even if the
waste is essentially totally combusted. Due to the short gas residence times
of a liquid injection unit, these "hot spots" may occur and carbon monoxide
may be channeled out of the combustion chamber. An engineering estimate on
combustion zone carbon monoxide levels that may be encountered would therefore
range from zero to 500 ppm. Based on actual liquid injection incinerator
combustion zone monitoring data, however, CO levels below 100 ppm are more
likely.
The moisture content of the combustion gases is highly dependent upon the
moisture level of the waste being fired, and to a lesser extent on the
relative humidity of the combustion air and the water vapor formed during
waste combustion. The practice of incinerating a waste stream with a high
( 50 percent) moisture content is not economically attractive due to the high
cost of auxilliary fuel and the inherent inefficiency of heating and
vaporizing water. Yet it may be the easiest way to dispose of a wastewater
stream contaminated with organics, and is therefore not uncommon. The
moisture level within a combustion zone can vary considerably and levels
measured during actual tests vary from 8 to 15 percent, as indicated in
Table 7 none of these wastes contained a high moisture content, it is
estimated that moisture levels may be higher, and an expectable range would be
5 to 20 percent.
Sulfur dioxide and hydrogen chloride concentrations within the combustion
zone are also dependent upon individual facility firing practices. For
example, as a worst case, if the incinerator is used to incinerate only those
Appendix VIII substances with the maximum sulfur or chlorine concentrations
(hydrogen sulfide—94 percent S, hexachloroethane—89.6 percent Cl) and no
excess air is used, then the combustion gases could contain up to 26 percent
S02 or up to 16 percent HC1. These values would be theoretical maximum
40
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concentrations. Realistically, no incinerator would be operated without some
level of excess air and this would serve to dilute these concentrations.
Furthermore, hazardous waste incinerators would be expected to burn a mixture
of wastes, and the composition of the mixture would not be expected to
approach theoretical maximums, especially in the case of sulfur. The limited
amount of test data reported in Table 7 for these pollutants indicates
measured S02 levels up to 200 parts per million and hydrogen chloride levels
slightly in excess of 6 percent. Yet, these levels would seem to understate
the actual potential for SC>2 and HC1 emissions. The problem with setting
realistic ranges for both S0~2 and HG1 combustion zone concentrations is
determining what is representative. What combination of wastes will be
incinerated together, and based on their chemical composition, what are the
expected combustion zone SC>2 and HC1 levels? One insight into realistic
sulfur containing wastes that may require incineration is the aforementioned
study done on pesticide disposal." one of the pesticides incinerated in
this study was malathion, with a sulfur content of 19.4 percent. This
substance was diluted with solvent and burned at an effective (mixed) sulfur
concentration of 11 percent. The resulting combustion zone SC>2
concentration was in excess of 3000 ppm. Allowing for the fact that 90
percent of the Appendix VIII sulfur containing compounds have a sulfur content
less than 50 percent by weight, and that when incinerated, the sulfur content
of their mixture would be less than half of their pure substance
concentrations, it is estimated that the maximum sulfur content of a waste, as
fired (including the dilution affects of auxiliary fuel) would be
approximately 20 to 25 percent. Therefore, the estimated maximum combustion
zone sulfur dioxide concentration range will be 0 to 5000 ppm. Should a
compound with an extremely high sulfur composition such as f^S or carbon
disulfide (C&2—84 percent S) be burned in a relatively pure state, then
higher S02 concentrations will occur. This possibility is assumed to be
remote.
Similarly, the likelihood that the maximum chlorine content waste
(hexachloroethane) will be burned in a pure state is also remote. The
organochlorine waste cited in Table 7 has a chlorine content of approximately
63 percent, and resulted in a HC1 level of 6.2 percent in the combustion
gas.2" if a waste with a higher concentration of chlorine is burned, then
higher combustion gas HC1 would result, but auxiliary fuel would be required
to support combustion, and the products of fuel combustion would tend to
dilute the HC1 concentration. These factors should balance each other out,
and the resulting flue gas HC1 concentration would be about the same. For
this reason, it is estimated that the practical range of HC1 concentrations is
0-7 percent.
Nitrogen formation is dependent upon both incinerator operating
temperature (thermal NOX) and waste nitrogen content (fuel NOX). As
liquid injection incinerators can operate at higher temperatures than the
other two incinerator designs, these units will emit more thermal NOX. Data
taken during liquid incinerator tests to date report combustion zone NOX
emissions in the 500 ppm range. This is primarily thermal NOX since the
wastes contained little bound nitrogen. Combustion zone NOX concentrations
reported during the incineration of a pesticide that did not contain nitrogen
41
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exceeded 1300 ppm," so this level is perhaps closer to the maximum thermal
NOX concentrations that might be expected. However, the major unknown in
estimating total NOX from an incinerator is the contribution of fuel NOX.
Appendix VIII wastes can contain up to 85 percent bound nitrogen.
Incinerators burning wastes with high nitrogen contents have emitted NOX in
the 5000 to 10,000 ppm range, according to one incinerator manufacturer.^7
Yet, if the NOX levels become extreme, many incinerator operators will
install a reduction furnace before or after the incinerator combustion zone to
minimize NO., emissions. There appears to be no set NO,, level where a
A 0 /
reduction furnace is mandatory.'" Each incinerator installation is designed
to meet customer specifications which are, in turn, set by local air quality
regulations. Taking this wide variety of factors into account, combustion
zone NOX levels are estimated to vary from 0 to 5000 ppm, with most
incinerators emitting less than 1500 ppm.
Rotary Kiln
The reactions within a rotary kiln incinerator are less severe than those
of a liquid injection combustion chamber. Temperatures and pressures are
generally lower, and the excess air level and average gas residence times are
higher, leading to a more oxidizing environment and a diluted pollutant stream.
Typical combustion zone temperatures within the kiln can range from 260
to 1260°C (500 to 2300°F) as shown in Table 7. This wide temperature range
reflects the versatility of a rotary kiln in accepting and destroying at ideal
temperatures liquids, solids, and sludges. Since most rotary kiln hazardous
waste incinerators are operated with an afterburner to destroy residual
organics, it is important to note these temperatures as well. Afterburners
are typically operated at temperatures ranging from 870 to 1540°C (1600 to
2800°F).2 The limited test data available on rotary kiln burns indicates
that the incinerator can be operated at whatever temperature is required to
destroy the waste fired, and that, as in the case of the FOB burn, the kiln
section may be bypassed and the waste fired directly into the afterburner if
this is compatible with system design.
Rotary kilns operate at a slight negative pressure. 1*> The principal
air movement equipment in these systems is an induced draft fan which is
typically installed immediately before the stack and which causes the negative
draft (-1.0 in w.g.) inside the kiln. Solids are fed into the kiln by gravity
while liquids and sludges are injected under pressure. However, this pressure
serves principally to atomize and disperse the wastes and is readily
dissipated within the large volume of the kiln. When liquids are injected
directly into the afterburner, this unit may operate at a slight pressure,
much like a liquid injection incinerator. This condition is site, as well as
burn, specific.
42
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There is a wide variation in air volumes used in the operation of rotary
kilns.18 Some kilns are operated in a starved air mode (50 to 100 percent
of stoichiometric air). Others are operated with up to 150 percent of excess
air (250 percent of stoichiometric). This demonstrates some of the
versatility of these units. Since rotary kilns burning hazardous wastes are
always operated with an oxidizing secondary combustion chamber (afterburner),
the net result is an overall excess air usage of 50 to 200 percent. A recent
survey of hazardous waste incinerators1° showed that the smaller rotary
kilns (5 to 20 million Btu/hr) may or may not operate under starved air
conditions, but the larger units nearly always operate with excess air in the
kiln. Since it is usually desirable to maintain the afterburner at a higher
temperature than the kiln, and because only liquid wastes or auxiliary fuel is
fired in the afterburner, the excess air rate in this device can usually be
controlled to less than that in the kiln. Rotary kiln excess air rates will
typically vary from 100 to 210 percent while those maintained in the
afterburner will range from 80 to 180 percent.2
The higher excess air rates in a rotary kiln versus a liquid injection
incinerator result in higher kiln oxygen levels and lower carbon dioxide
concentration in the combustion zone. Based on the standard excess
air/oxygen/carbon dioxide relationships presented in Figure 8, rotary kiln
oxygen levels can be estimated to vary from 9 to 12 percent, while carbon
dioxide concentrations will range from 4 to 10 percent. Monitoring data taken
from actual rotary kiln test burns confirms these ranges.
The higher excess air level and longer residence time of rotary kilns
also serves to minimize the carbon monoxide concentration within the
combustion zone of these units. Carbon from both the waste and any auxiliary
fuel used is exposed for a longer time to an atmosphere which is richer in
oxygen. This enhanced oxygen environment promotes the reaction to carbon
dioxide at the expense of unburnt carbon and carbon monoxide and minimizes
carbon monoxide levels. An engineering estimate of actual carbon monoxide
levels within the combustion zone would be 0 to 100 parts per million.
The moisture levels within a rotary kiln combustion zone are like those
of the liquid injection unit, dependent primarily on the moisture level of the
feed. Identical wastes fired into either incinerator would result in
identical moisture levels. However, the increased excess air level of the
rotary kiln would generally tend to dilute these levels. The specific affect
of this increased excess air depends upon its moisture content. Excess air at
20°C (68°F) and 50 percent relative humidity would contain only 1 percent (by
weight) water, while the same air at 50°C (122°F) and 50 percent relative
humidity would contain over 4 percent moisture. Higher temperature combustion
air with a high relative humidity will lend a proportionally greater amount to
total moisture levels, but will never outweigh the affect of a high moisture
content waste. An engineering estimate of typical moisture levels within the
rotary kiln would therefore be from 3 to 15 percent.
Since sulfur dioxide and hydrogen chloride concentrations are depeadent
upon the composition of the waste, their formation is not affected, per se, by
43
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the type of incinerator used. However, once formed, these pollutants will be
diluted by the excess combustion air present. As rotary kilns operate with
3 to 5 times the excess air levels of liquid injection units, we can conclude
that pollutant concentration estimates developed for these units can be
diluted by a comparable factor. Therefore, an engineering estimate of sulfur
dioxide levels would be 0 to 1500 ppm and one for hydrogen chloride would be
0 to 2 percent. There is little or no actual combustion zone monitoring data
available to substantiate these estimates. Should the rotary kiln be used in
the starved air mode, as previously mentioned, then these estimates would hold
true only for the afterburner section.
Nitrogen oxide formation is less severe with rotary kiln incinerators
than with liquid injection units. Although the rotary kiln operates at a
higher excess air rate and therefore has a greater amount of oxygen available
for NOX production than the liquid injection incinerator, it generally
operates at a lower temperature and this is the controlling factor. As
discussed earlier, the incinerator operating temperature is the principal
variable in thermal NOX production and peak operating temperature of only a
few hundred degrees can produce a noticeable affect on NOX emissions. Fuel
NOX production from rotary kilns should be comparable to that of liquid
injection units, and may predominate if high nitrogen containing wastes are
burned. It appears that the most important parameters in determining fuel
bound nitrogen conversion appears to be the local conditions prevailing when
the nitrogen is evolved from the fuel. Under fuel to rich conditions, this
nitrogen tends to form N2> whereas under fuel to lean conditions,
significant amounts of NOX are formed.2° it is difficult, however, to
quantify the affect of this phenomena on NOX generation in the various
incinerators reviewed in this report. The few tests to date which have
measured combustion zone NOX levels in rotary kilns demonstrate lower levels
than similar data from liquid injection incinerators. An engineering estimate
of the maximum range of NOX levels that may be experienced in this zone is
0 to 2000 ppm, with typical levels below 1000 ppm.
Fluidized Bed
Fluidized bed incinerators operate with the least severe conditions of
any of the three types investigated. The temperature, pressure and pollutant
concentration levels within the combustion zone of these units are lower than
the other incinerator designs. However, there is limited data available on
combustion zone characteristics of fluidized bed incinerators when burning
hazardous wastes and the available test data at times contradicts published
design information. A review of combustion zone operating parameters for
these units should keep in mind the ambiguity of available data.
Two combustion zone temperatures are generally referred to with respect
to fluidized bed incinerators: bed and freeboard. Bed temperatures refer to
the temperature within the bed of granular material where the waste is
introduced. Bed temperatures are generally in the range of 450 to 810°C (840
to 1490°F).2 The freeboard zone is the area directly above the bed where
the hot combustion gases separate from the bed material. Combustion of wastes
44
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is completed in this zone and temperatures are higher than bed temperatures,
typically ranging from 600 to 980°C (1110 to 1800°F).2 As noted in Table 7,
testing has been conducted on a fluidized bed unit which was operated at
temperatures in excess of this range. While uncommon in its high temperature
and excess air levels, this test series serves to emphasize that the typical
parameter ranges stated in Table 7 are not absolute ranges and may in certain
situations be exceeded.
The pressure within a fluidized bed unit will vary, depending on where
the measurement is taken, since both forced and induced draft fans are used.
The waste being incinerated is usually injected into the bed under pressure.
In addition, the fluidizing air which acts to suspend the bed material is also
injected by forced draft fan into the bed under pressure. Consequently, there
is a positive pressure within the bed itself. This pressure decreases as the
air flows into the freeboard space above the bed, and the action of the
induced draft fan dominates. The specific bed pressure and whether it is
positive or negative therefore depends upon the monitoring location within the
bed. A typical pressure reading could vary from +1.0 in. w.g. (in the
bed)—2.0 in. w.g. (in the freeboard space).
There is somewhat of a contradiction in the literature concerning excess
air rates for fluidized bed incinerators. Theoretically, these units can be
run at low air levels, from 10 to 50 percent in excess of stoichiometric
1 f\ 1 7
requirements.i0»1/ In fact, one of the advantages of these incinerators is
the low excess air requirements which minimizes the size and therefore the
expense of the related air pollution control equipment. This relative
advantage is contradicted by the data obtained from actual hazardous waste
tests, as presented in Table 7. These data (two sets of tests conducted on
each of two separate units) indicate excess air levels in the combustion zone
exceeding 100 percent for each test series. The fluidized bed units for these
tests were operated primarily to ensure complete (99.99 percent) destruction
of the influent waste stream. Combustion air, far in excess of the amount
required for complete waste destruction, was probably used as a precautionary
measure and the economic penalties associated with handling and cleaning this
larger volume airstream were accepted. For this analysis, we will assume that
these higher excess air levels were atypical and that the actual levels that
will be encountered in the field will be closer to the normal range of 10 to
50 percent.
This excess air rate assumption will also affect our estimates for oxygen
and carbon dioxide levels in the combustion zone. Excess air levels of 10 to
50 percent translate to oxygen levels of between 2 and 8 percent and carbon
dioxide concentrations ranging from 10 to 17 percent of the combustion gases.
Should the fluidized bed unit be run with high excess air levels, as those for
which test data is presented in Table 7, then the oxygen levels would approach
14 percent and the carbon dioxide levels 10 percent.
Regardless of the assumed excess air levels, carbon monoxide
concentrations are low in the fluidized bed incinerator. The intense
agitation of the bed material promotes turbulence and good mixing of waste and
45
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fuel, thereby minimizing the formation of incomplete combustion products such
as carbon monoxide. As is evident in Table 7, there is only one data point
for fluidized bed combustion zone carbon monoxide level, which is a maximum
concentration of 25 ppm. Allowing for the fact that the high excess air level
for this test series may have depressed typical expected CO concentrations, it
is estimated that a typical carbon monoxide range would be 0 to 100 ppm.
Moisture levels are affected by both the moisture content of the waste,
the water vapor formed by the combustion of hydrogen, and the relative
humidity of the combustion air. Since one of the advantages of the fluidized
bed incinerator is its ability to handle high water content wastes such as
sludges, it is expected that the moisture content of the incinerated waste
could approach 80 to 90 percent. An engineering estimate of the range of
expected flue gas moisture levels would therefore be 5 to 25 percent. No data
on actual combustion zone moisture concentrations could be found in the
literature.
Estimates of both sulfur dioxide and hydrogen chloride concentrations
should be based, as before, on the maximum sulfur and chlorine concentrations
of the Appendix VIII waste and the amount of dilution air attributable-excess
air. Following this technique, the maximum SC>2 and HC1 concentrations in
the combustion zone of a fluidized bed incinerator should be higher than the
other incinerators, since the normal excess air level is lower. However,
there are other factors that would play a part, should these pollutant levels
become excessive. Specifically, the bed material can be altered to allow for
the adsorption of acid gases, by adding lime or some other caustic solid.
Since this can be accomplished with only minor modifications to the system,
and since adsorption of acid gases in the bed would reduce the need for
further protection of incinerator internals downstream, such a practice would
probably be adopted for wastes with high sulfur and/or chlorine contents in a
fluidized bed incinerator. Based on this assumption, it is estimated that the
range of sulfur dioxide concentrations, as measured in the freeboard space,
would be in the 0 to 1000 ppm range, and HC1 levels would be 0 to 1 percent.
Nitrogen oxide concentrations in the combustion zone of a fluidized bed
incinerator will be the lowest of any of the three incinerator designs
reviewed. This is attributable to the relatively low temperature and low
excess air level at which these units are operated. Only one of the test
series conducted on fluidized bed units while burning hazardous wastes
measured NOX levels. This test reported a maximum concentration of 25 ppm.
Based on currently available data, a best engineering judgement of combustion
zone NOX concentrations is 0 to 1500 ppm. This range assumes that the
thermal NOX level is much less than the other incinerator designs and that
when a high nitrogen content hazardous waste is burned, the contribution of
fuel NOX is comparable.
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PRE-APC DEVICE MONITORING LOCATION
Monitoring hazardous waste combustion flue gas parameters before an air
pollution control device has not been reported in the literature. The
principal purpose of such monitoring would be to verify control device
efficiency. Estimates of expected flue gas characteristics must therefore be
made using best engineering judgement, based on combustion zone conditions and
changes that may occur to the gas stream between the combustion zone and the
air pollution control device.
As discussed in Section 3, some form of heat recovery or water quenching
is usually practiced on the gaseous effluent of hazardous waste incinerators
to reduce total flue gas volume. Therefore, as a point of reference, the
pre-control device monitoring zone will be defined as being located after this
cooling zone, and immediately proceeding the control device. This definition
enables us to limit our analysis of monitoring parameters to the affects of
flue gas cooling or conditioning. As will be shown, only a few flue gas
parameters are changed when the temperature of the gas stream is lowered, and
due to the similarity of flue gas cooling devices, these changes will be
similar for the various types of incinerators. The various parameters and
their ranges of values will be defined, again by incinerator type. All
parameter estimates at the monitoring zone immediately before the air
pollution control device (pre-APC device) are presented in Table 8.
Liquid Injection
A liquid injection incinerator will be followed by a heat recovery device
or a quench section/conditioning tower depending on the magnitude and extent
of pollutants generated. During waste incineration, if the gas stream is not
excessively corrosive, a heat exchanger will be used to recover valuable
energy, otherwise the gas stream will be simply cooled using water sprays.
Heat recovery units, either heat exchangers or waste heat boilers, simply
lower the temperature of the flue gases by transferring the heat to another
medium, such as air (e.g. heat exchanger) or water (e.g. waste heat boiler).
These units are commonly used when no appreciable amount of S02> NOX, or
HC1 or other pollutants are generated that can potentially erode internal
metal surfaces, or when the outlet temperature of the heat recovery device can
be maintained above the condensation temperature of the acid gases, thereby
limiting corrosion and erosion.
A quench or conditioning section utilizes the evaporation of water to
lower the flue gas temperature and reduce the volume of flue gas that must be
treated. Since the concentrations of gaseous constituents in the flue gas
(02, C02j CO) and gaseous pollutants (S02, HC1, NOX) are measured on a
dry, water free basis, these concentrations will not be altered. However, it
must be noted that the addition of water will add to the total mass of the
flue gases and on an absolute basis, these concentrations will be altered.
Since a continuous emission monitoring system will usually condition the gas
stream (remove moisture) before measuring its components, the convention of
stating gaseous concentrations on a dry basis will be retained. A quench
47
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section is typically used before a scrubber, when flue gas volume reduction is
the prime concern. A conditioning tower also utilizes water to lower gas
temperature, but the final gas temperature is higher and will vary depending
on whether an electrostatic precipitator or a fabric filter is installed for
particulate control. With this background in mind, we can examine specific
flue gas parameters.
Due to design considerations, the flue gas temperature exiting a heat
recovery device is usually limited to a minimum of approximately 150°C
(300°F). This will be the typical temperature if a fabric filter or a
scrubber follows heat recovery. If an electrostatic precipitator is the
collection device in use, or if acid gas condensation is to be avoided, the
typical heat recovery exit temperature is 315°C( 600°F). A quench tower is
almost always followed by a wet collection device, either an absorber for acid
gas removal, or a venturi scrubber for combined particulate and gaseous
pollutant cleaning. Quench tower exit temperatures will vary from 65 to 175°C
(150 to 350°F), although if the lower temperature is reached, acid gases will
begin to condense on internal surfaces and some form of corrosion protection
must be employed. In certain cases where a venturi scrubber is utilized, no
quenching is employed and the gas temperature at this monitoring location can
approach 1090°C (2000°F).29 These cases are somethat uncommon and have not
been affected in the estimated average temperature range.
As noted in Table 8, the pressure of the combustion gases that exit the
liquid injection incinerator can range from -4 to +10 inches, water gauge (in.
w.g.). This pressure will become increasingly negative as the gases get
closer to the inducted draft fan inlet. At the Pre-APC device monitoring
location, the range of potential pressure can be estimated to equal the sum of
the incinerator pressure, plus the pressure drop across the cooling section.
Waste heat boilers have an estimated pressure drop of from 2 to 6 in. w.g.,
depending on the number of sets of tubes, the existence of an airheater, etc.
When added to the furnace outlet pressure, this results in an estimated
monitoring zone pressure from -10 to +8 inches, water gauge. Quench towers
have a much lower pressure drop, from 0.1 to 0.5 in. w.g. Therefore, if these
devices are used, the overall pressure at the monitoring zone may vary from
-5 to +10 in. w.g. It must be emphasized that these estimates assume that the
position of the fan is downstream of the air pollution control equipment, near
the exhaust stack. If the fan is located between the incinerator and the
cooling section or if multiple fans are used, then the aforementioned
estimates may not hold true. The most common process flow arrangement is that
which has an induced draft fan located immediately before the exhaust stack
and is used to determine monitoring zone parameters for all values stated in
this section.
Any changes in the excess air, oxygen and carbon dioxide concentrations
of the flue gas at this monitoring location will occur if there are leaks in
the ductwork and/or the cooling equipment. If the system is operated at a
negative pressure in the cooling region, any leakage would cause an
49
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infiltration of outside air into the flue gases and result in higher amounts
of excess air and oxygen, and a lower carbon dioxide concentration. For this
study, however, we will assume that the incinerator and its associated systems
are rigorously inspected and maintained and that any noticeable deterioration
of the system is immediately repaired. This assumption precludes the influx
of ambient air and allows us to estimate that the excess air, oxygen and
carbon dioxide percentages of the flue gas are identical to those at the
combustion zone. Excess air would be in the 20 to 60 percent range, oxygen
from 4 to 9 percent, and carbon dioxide from 8 to 16 percent.
Carbon monoxide (CO) concentrations will be lower in the Pre-APC device
monitoring location than they will be in the combustion zone. Carbon monoxide
destruction is related to both temperature and residence time, as shown in
Figure 9. The longer CO is allowed to remain in high temperature oxidizing
environments, such as that which is present in the flue gas exiting the
incinerator, the lower will be the final CO concentration. While this
elevated flue gas temperature is only maintained until the gases pass through
the cooling sections, this additional residence time should be sufficient to
Ibwer CO concentrations appreciably. The extent of this reduction can only be
estimated, and this engineering estimate would place CO concentrations at
between 0 and 100 ppm, or a reduction of approximately 80 percent.
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Figure 9. Carbon monoxide destruction efficiency.
50
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The moisture content of the gases will of course be greatly influenced by
the type of cooling device used. Waste heat boilers add no moisture to the
gas stream, and the gas compositions of the flue gases after these devices is
within 5 to 20 percent the same as that exiting the incinerator. Use of a
quench chamber adds significant amounts of water to the gas stream. Depending
on the temperature of the gases as they leave the quench section, from 35 to
40 percent of the volume of the total gas stream is water added in the quench
chamber. When added to the moisture present in the waste, the total moisture
content at this monitoring location is estimated to be 40 to 60 percent.
There will be no change in the sulfur dioxide, hydrogen chloride or
nitrogen oxide concentration of the flue gases between the combustion zone and
the Pre-APC device monitoring zone. While the temperature and therefore the
volume of flue gases will be greatly reduced, the pollutant volumes will be
reduced proportionately and therefore the pollutant concentrations will remain
unchanged (assuming ppm levels of pollutants). Due to the lower temperature,
there may be a change in the concentration of nitrogen dioxide since it is
water soluble, but the overall NOX concentrations will not be appreciably
affected. Furthermore, it is assumed that if a quench section is used, only
enough water is added to lower the temperature. Excess water added in the
quench will serve to lower the flue gas below the dewpoint of these pollutants
and will scrub some of the gaseous pollutants from solution, thereby reducing
their concentrations. This is assumed not to happen since it would require
that some method of removing and neutralizing these gases be provided in this
section. Nonetheless, facility operators will often line their quench
chambers with an acid resistant material to protect the internal surfaces
should an operating problem occur that results in excess water addition and
the subsequent condensation of acid gases.^2 jf j,y design or accident,
water is added in the quench chamber far in excess of what is needed to simply
cool the gases, then the concentrations of SC^, NOX and especially HC1
will be lower than those estimates in Table 8. These Table 8 figures
therefore could be considered maximum values. The estimates established for
the three gaseous pollutants at the combustion zone will be unaffected by
cooling and will remain unchanged; 0 to 5000 ppm for 862, 0 to 7 percent for
HC1 and 0 to 5000 ppm for NOX.
Rotary Kiln
An analysis identical to that for liquid injection incinerators was
conducted for rotary kiln units. The parameter ranges presented for the
combustion zone in Table 7 will serve as an initial set of conditions and the
affects of cooling on these conditions will be discussed.
Flue gases exiting a rotary kiln will be treated similar to those from
liquid injection incinerators; they will be cooled by means of a waste heat
boiler or a quench chamber/conditioning system. Due to its versatility, a
rotary kiln may be used for a wide range of waste types and compositions.
Waste heat recovery is less likely to be practiced when the waste quantity and
composition fluctuate widely, as might be expected in a diversified industrial
complex.30 Fluctuations affect the reliability of the heat recovered and
thus the economics of this auxilliary system. When practiced, waste heat
51
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recovery lowers the flue gas temperature to approximately 150 to 315°C (300 to
600°F) depending on the type of device utilized. A quench chamber can lower
the temperatures even more, to the 65 to 175°C (150 to 350°F) range. As with
liquid injection processes, the temperature at the Pre-APC device monitoring
location depends upon the type of APC device installed, and this device
depends on the type and amount of pollutants generated.
As stated earlier, the pressure drop across a waste heat recovery boiler
may range from 2 to 6 in. w.g. and for a quench chamber from 0.1 to 0.5 in.
w.g. When added to the slight negative pressure that exists at the rotary
kiln outlet, the pressure at the Pre-APC devicejaonitpring location will vary
from -2.5 to -8.0 in. w.g. for waste heat applications from -0.6 to -2.5 in.
w.g. for quench chamber installations.
As with liquid injection incinerators, rotary kilns are assumed to be air
tight, with no leakage of ambient air into the flue gas stream. While
maintaining a tight air seal at the incinerator end may be an operational
problem for rotary kilns,^0 the potential air infiltration at this point has
been accounted for in the high excess air rates estimated for these units
under combustion zone conditions. The excess air rate, and oxygen and carbon
dioxide levels, will be assumed identical to those at the combustion zone; 80
to 210 percent excess air, 9 to 12 percent oxygen, and 4 to 10 percent carbon
dioxide.
The carbon monoxide concentration for rotary kilns is also estimated to
be reduced due to the increased residence time at the high temperature
oxidizing atmosphere the carbon monoxide will experience. Since the oxygen
concentration is even greater with rotary kilns than it is for liquid
injection incinerators, the reduction in carbon monoxide should be
proportionately greater. Yet, as the CO concentration is lowered, oxidation
of the residual amount remaining becomes more difficult. Therefore, it is
estimated that the carbon monoxide concentration at this point is lower in
rotary kilns than it is for liquid injection units, even if the percent
reduction from the combustion zone to this monitoring site is not as great.
An estimated CO range would be 0 to 50 ppm.
The moisture content of the flue gas will be dependent on whether heat
recovery or water quenching is used to cool the gas stream. As with liquid
injection incinerators, the flue gas from rotary kilns will maintain its
moisture content if some form of dry cooling, such as heat recovery, is used.
The combustion chamber moisture level of 3 to 15 percent would be maintained
in these cases. If, however, water quenching is employed, then the flue gas
stream moisture content will be raised by, 35 to 40 percent, or to a total of
approximately 40 to 50 percent.
Concentrations of the specific pollutants of interest in this study,
sulfur dioxide, hydrogen chloride and nitrogen oxides, are measured on a dry
basis, and should not be affected by any increase in flue gas moisture
content. As stated before, these pollutant levels would be affected if
excessive water is added in the quench chamber and the flue gas temperature
falls below the dew point of these compounds. But, we have assumed that this
52
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does not occur and that the pollutant concentrations, on a dry basis,
essentially remain the same as those in the combustion chamber; 0 to 1500 ppm
for S02, 0 to 2 percent for HC1, and 0 to 2000 ppm for NOX.
Fluidized Bed
The flow of combustion gases from a fluidized bed incinerator is similar
to that from the other incinerator types. The gas stream is passed through
either a heat recovery device or a water/quench conditioning section where the
temperature is lowered to a level compatible with the air pollution control
device into which the gas stream will flow. These final temperatures are
identical to those previously described for the other incinerators; 150 to
315°C (300 to 600°F) for gases exiting a dry heat recovery device, and 65 to
175°C (150 to 350°F) for gases leaving a water quench. Again, the exact
temperature will depend upon the type of air pollution control device
installed.
The pressure of the gas stream also depends on whether a heat recovery
device or a quench chamber is used. As discussed earlier, there is a wide
range of possible pressure losses, depending on which type of cooling
equipment is used. Quench chambers, which employ water sprays, have a low
pressure drop, ranging from 0.1 to 0.5 in. w.g. Simple air to air heaters
have a slightly higher pressure drop, some 1 to 3 in. w.g. while waste heat
recovery boilers have the greatest loss of pressure, some 2 to 6 in. w.g. All
fluidized bed units will utilize a blower or fan to supply combustion/
fluidizing air at the base of the bed, and a second fan, typically located
immediately before the exhaust stack. The likelihood that this second fan
will be located between the combustion zone and the air pollution control
device is slight. Therefore, there is little likelihood that there will be an
increase in gas pressure either before of after the cooling section. The
pressure drop across the cooling device will serve to lower the existing
combustion zone pressures. The estimated gas pressure at the pre-APC device
monitoring zone location will range from -1.0 to -8.0 in. w.g. For
installations with heat recovery devices to -2.5 to +0.9 in. w.g. for
processes that utilize water quenching. The small relative difference in the
range of gas pressures for fluidized bed units vis a vis the other
incinerators is maintained at this monitoring location.
The discussion of excess air rates, and oxygen and carbon dioxide
concentrations that was presented earlier for the other incinerators holds
true for fluidized bed units as well. Assuming there are no leaks where
ambient air can infiltrate and dilute the flue gases, the range of these
parameters will remain unchanged at 10 to 50 percent excess air, 2 to 8
percent oxygen, and 10 to 17 percent carbon dioxide.
Carbon monoxide levels should be lower at this monitoring location due to
the increased opportunity for further oxidation. Since the flue gas oxygen
concentration for fluidized bed incinerators is lower than that for rotary
kilns, the carbon monoxide reduction may not be as great. Yet, it is assumed
that a minimal reduction of 50 percent does take place, and that the estimted
range of carbon monoxide concentrations at this monitoring location will be
0 to 50 ppm.
53
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Flue gas moisture levels are dependent on the addition, if any, of water
in the cooling zone. For dry cooling devices, no moisture is added, and the
combustion zone moisture content estimate of 5 to 25 percent is maintained.
For quench chambers, an additional 35 to 40 percent, by volume, moisture is
added, thereby raising the total moisture content to 40 to 65 percent.
Finally, without the addition of ambient air, the concentrations of
sulfur dioxide, hydrogen chloride, and nitrogen oxides on a dry basis will be
the same as for the combustion zone; 0 to 1000 ppm for S(>2> 0 to 1 percent
for HCl,and 0 to 1500 ppm for NOX.
POST APC DEVICE
The final monitoring zone of concern with respect to continuous emission
monitoring parameters is the stack or post air pollution control device site.
By the time hazardous waste incinerator effluent gases reaches this point,
they will have been conditioned, cooled and cleaned. Final stack gas quality,
from an air pollution standpoint, will be set by applicable Federal, state and
Icoal air quality regulations. The federal regulations for hazardous waste
incinerators were stated in Section 4. Since hazardous waste incineration is
still an emerging technology, many state and local regulations have yet to
establish regulations limiting stack emissions. As a result, a wide range of
possible flue gas concentrations is possible. None-the-less an estimate of
stack parameters can be stated, based on standard air pollution strategies.
Once again, this analysis will proceed from the last monitoring zone, located
before the APC device, to the stack site, and will quantify the effects of air
cleaning on flue gas parameters. All flue gas parameter estimates are
reported in Table 9.
Liquid Injection
As with the pre-APC device mentoring zone, flue gases at the stack
location can be generally categorized as being either "dry" or "wet." These
designations refer not only to the method of flue gas cooling, but also to the
type of air pollution control employed. Dry APC devices which include
electrostatic precipitators (ESPs) and fabric filters will be used when
particulates are the only emission of concern. Electrostatic precipitators
will typically be operated in the 150 to 315°C (300 to 600°F) range while
fabric filters have a practical upper operating limit of 145°C (290°F).^
Both devices have a lower temperature limit that is set to avoid condensation
of water or any acid gas in the flue gas on the internals of the device. In
addition, fabric filters have the additional consideration of bag plugging due
to condensation of organics, water and/or acid gases. While the specific
minimum temperature is determined by the flue gas composition and the
corresponding acid gas dew points, a practical minimum temperature is
approximately 90°C (200°F). Allowing for a 10 percent loss in temperature
between the air cleaning device and the stack, it is estimated that dry
collection devices will have stack temperatures in the 80 to 280°C (175 to
535°F) range.
54
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Wet collection devices will have a much narrower temperature range.
Regardless of the inlet temperature to the device, the maximum outlet
temperature will be 100°C (212°F). The flue gas in this condition would be
completely saturated with water and would most likely be vented through some
form of mist eluminator to remove entrained water droplets. Temperatures as
low as 65°C (150°F) have been reported at the scrubber outlet,^ and this is
a realistic lower limit for these devices. Again allowing for a 10 percent
temperature reduction from the scrubber and/or mist eliminator, to the stack,
the temperature range for wet collection devices would be 60 to 90°C (140 to
195°F).
The flue gas pressure at the stack monitoring location will depend on
both the affects of the prime air movement fan and the natural draft and
related negative pressure that occurs in a stack due to the stack height.
Incinerator systems typically utilize an induced draft fan, located between
the final AFC device and the stack, to pull combustion gases through the
entire system. This fan will discharge air into the stack with a slight
positive pressure, typically 0 to 2 inches, water gauge. As the flue gas
enters the stack this pressure dissipates, and the stack draft begins to
predominate. Stack draft is a natural negative draft that occurs in the stack
due to elevated temperature of the stack gases and the height of the stack.
The stack draft will typically range from 0 to -2.0 in. w.g. The actual
pressure of the flue gases will therefore depend on these two factors, and
where the measurement is being taken. A positive pressure will be measured
closer to the fan outlet while the pressure will be increasingly negative as
the gases move up the stack and the natural draft affect takes over. A range
of stack pressures, regardless of the type of air cleaning employed would
therefore be -2.0 in. w.g. to +2.0 in. w.g.
The excess air rates and related oxygen and carbon dioxide concentrations
at the stack monitoring location should not change dramatically from the
pre-APC device site. This is attributable to restrictions in total system air
flow which are established by the induced draft fan. Since the fan is
designed for overall system air flow requirements, any substantial leakage of
ambient air into the system will overload the fan. This condition will
potentially lead to poor system performance in terms of lower pollutant
collection efficiencies and should be noticed by changes in key process
parameter indicators, such as pressure drop and temperature. Thus, while some
air leakage before the fan is possible, extensive leakage is unlikely to be a
long term problem. Air infiltration between the fan and the stack is more
likely to account for such leakage. It is estimated that the total excess air
rate will increase by approximately 20 percent, thereby changing the range for
this parameter from 40 to 80 percent. No actual test data could be found to
substantiate this estimate. In addition, it is recognized that individual
facilities may have higher excess air rates, depending on operating and
maintenance conditions. The corresponding range of oxygen concentrations for
this excess air estimate will be approximately 6 to 10 percent, for both dry
and wet APC devices. The range of carbon dioxide concentrations at the stack
site will be different depending on whether a wet scrubber is used, and also
depending on the alkali which is used in conjunction with the scrubber. Carbon
56
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dioxide is, itself, an acid gas. It will react with alkaline solutions and,
to a limited extent, be scrubbed from the flue gases. For example, the
overall mass transfer rate for CC>2 removal in a sodium hydroxide scrubbing
solution is as much as one third that of the more common acid gas, sulfur
dioxide.^ Due to the number of variables involved in calculating the exact
COo removal efficiency in a system, only a qualitative estimate can be
made. It is projected that a standard C02 range for dry systems will be
7 to 11 percent, while the range for wet systems may be closer to 6 to 10
percent.
Carbon monoxide is assumed to be unchanged by either the dry or the wet
collection devices. While some additional oxidation may occur, the relatively
low temperature of the flue gas as it traverses the APC device does not favor
significant conversion of CO to CC^- Therefore, the estimated range for CO
remains at 0 to 100 ppm.
The moisture content of the flue gases will depend on the type of APC
device employed. For dry devices, no additional water is added and the
estimated moisture content remains at 5 to 20 percent. For wet collection, an
interesting phenomena can occur across the collection device; if the outlet
temperature of the device is at the lower end of the range stated in Table 9,
the moisture content of the flue gas may, in fact, decrease. This is
attributable to the decreased ability of flue gases (and air) to retain
moisture at lower temperatures. Flue gas which is saturated at 90°C (190°F)
will contain 63.5 percent moisture. The same gas at 60°C (140°F) will contain
only 20 percent moisture. These two saturation capacities will therefore
define the maximum moisture content of the flue gases at the stack monitoring
location. The scrubber, in cooling the stack gas also acts as a condenser in
removing moisture from this gas. The resulting moisture levels (assuming
saturation of the flue gas) at the temperatures stated in Table 9, will vary
from 20 to 63.5 percent.
Estimation of stack gas acid gas levels is another area where there are a
number of indeterminate variables, each of which can affect concentration
estimates. The first of these variables is applicable regulation. The
Federal Regulation for hydrogen chloride is clear; 99 percent removal.
Applying this removal efficiency to the maximum estimated HC1 content given in
Table 8, we can estimate a stack gas HC1 range of from 0 to 700 ppm (0 to 0.07
percent). Due to the high degree of solubility of HC1 in water, removal
efficiencies in excess of 99 percent have been reported for scrubbers
utilizing water alone. Scrubbers employing a caustic solution have reported
collection efficiencies as high as 99.9 percent.^ For dry collection
systems, the maximum hydrogen chloride content is set by the corrosion
resistance of the equipment. For example, HC1 concentrations into ESPs are
kept below 1000 ppm and usually average 300 ppm.^ When the 20 percent
excess air dilution estimate is factored into the HC1 levels, the standard HC1
ranges would therefore be 0 to 400 ppm (0.04 percent) for dry APC devices and
0 to 560 ppm (0 to 0.056 percent) for wet collection.
57
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There are currently no broad-based sulfur dioxide emission limitations
for hazardous waste incinerators. Some states, such as New York, require that
any industrial incinerator remove greater than 90 percent of all acid
gases,32 including SOo- Many states have no such emission restriction.
As a result, it is difficult to make an estimate on stack gas 302
concentrations, especially for dry collection devices. Without knowledge of
specific applicable state regulations, a conservative estimate must assume
that no S02 removal is required and that the pre-APC device 502
concentration estimate of 5000 ppm remains unchanged except for the dilution
of additional excess air, resulting in a stack gas level of 4000 ppm. This
concentration is roughly twice the S02 level found in the stack gas of a
power generating facility burning coal with a sulfur content of 4 percent.
When wet scrubbers are employed, sulfur dioxide emissions will be removed
together with HC1. Sulfur dioxide removal efficiencies of up to 40 percent
have been reported at power stations, for scrubbers which were employed
primarily for particulate emission control.34 The use of alkali solutions
in scrubbers can boost S0£ removal efficiencies over 90 percent.^3
Technology, principally developed for the electrical power industry, is
currently available to lower flue gas sulfur dioxide emissions to virtually
any level desired.-" For the purpose of this report, it is assumed that
once a wet scrubber is to be installed for a hazardous waste incinerator, it
will be designed for S0£ removal efficiencies in excess of 80 percent.
Adding the additional dilution affect of infiltrating excess air, the range of
expected stack gas SO2 levels is estimated to be from 0 to 800 ppm.
Nitrogen oxide emissions are not amenable to control by scrubbing or
other post generation removal techniques. Excessive NOX emissions, if
present, must be addressed at the incinerator with the installation of a
reduction furnace. While the literature reports NOX removal efficiencies of
up to 25 percent can be obtained with certain scrubber designs, such removal
requires NOX levels in excess of 10,000 ppm. ^ This elevated NOX
concentration is unlikely in hazardous waste incinerator effluents, and thus
this scrubber efficiency is not applicable. Consequently the estimated NOX
range at the stack for both dry and wet processes will be the 5000 ppm level
assumed before the APC device diluted by an additional 20 percent excess air,
or 0 to 4000 ppm.
Rotary Kiln
Once the incinerator combustion gases exit the combustion chamber, the
control is dependent upon flue gas composition and not on the type of
incinerator employed. As a result the stack gas quality from all incinerator
designs is similar and the rationale that was presented for liquid injection
incinerators is equally applicable for rotary kiln and fluidized to bed units.
The estimated stack temperature is primarily a function of the type of
APC device employed. Electrostatic precipitators and fabric filters are
associated with higher temperatures due to the problems of acid gas
condensation previously discussed. Wet scrubbers operate at lower
temperatures due to the cooling affects of water. Allowing for these factors
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and a temperature loss from the control device to the stack, estimated
temperature ranges are 80 to 280°C (175 to 535°F) for dry collection, and 60
to 90°C (140 to 190°F) for wet air pollution control.
The analysis presented under liquid injection incinerators for stack gas
pressure is also applicable for rotary kiln effluents as the location of the
prime air movement fan in the system is identical. Stack pressure will vary
from 2.0 to +2.0 in. w.g., depending on where in the stack the measurement is
taken.
The assumptions in which the stack gas excess air rate and the oxygen and
carbon dioxide concentrations were previously based also holds true for rotary
kiln incinerators. Excess air should remain relatively constant through the
APC device, and then increase slightly due to potential leakage. For both wet
and dry control this increase is estimated at 20 percent, bringing stack
excess air estimates to between 100 and 230 percent.
The corresponding oxygen concentration for these excess air rates is also
identical for both wet and dry APC control, varying from 10 to 14 percent.
The carbon dioxide levels will be slightly different between dry and wet
devices due to the absorbtion of CC>2 in a wet scrubber. It is estimated
that incineration systems using dry AFC devices will have stack gas CO2
concentrations ranging from 3 to 8 percent, while those employing scrubbers
will have a 2 to 7 percent C02 range.
Carbon monoxide levels are assumed to be unchanged across the APC
device. The range given in Table 8 for the pre to APC location will be the
same at the stack; 0 to 50 ppm.
Flue gas moisture levels will be affected as discussed earlier; for dry
collection, the moisture content will remain at 3 to 10 percent. For wet
collection devices, the stack gas is assumed to be saturated with moisture at
the stack temperature, thereby setting the moisture content between 20 to 63.5
percent. Should the stack gas be reheated to avoid condensation of acid gases
on the stack walls,^" this moisture content may be somewhat lower.
Hydrogen chloride emissions will be limited by corrosion factors, in the
case of dry APC devices, and by federal regulatory requirements, as far as wet
scrubbers are concerned. Dry devices have a practical maximum HC1 limit of
approximately 500 ppm. Should HC1 concentrations in excess of this limit be
projected for a dry APC device, then dry scrubbing, waste blending or some
similar control technique will be used to minimize emissions into the device.
Dry scrubbing, for example, is capable of removing in excess of 99 percent of
HC1 and 85 percent of 862 from a gas stream.37 We will assume that the
500 ppm HC1 limit will be the maximum concentration that dry flue gas streams
will contain at the control device inlet, and that the addition of 20 percent
excess air between the fan and the stack will reduce this concentration to 400
ppm, or 0.04 percent.
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As discussed earlier, federal regulations require 99 percent control for
HC1. As the rotary kiln HCl emissions have been diluted by the higher excess
air rates of these units, both APC device inlet and outlet HCl emissions are
lower than similar liquid injection incinerator emissions. Ninety nine
percent control on a maximum inlet KCl emission level of 2 percent will result
in an outlet concentration of 200 ppm. If this concentration is further
reduced by the 20 percent excess air infiltration estimate, stack gas HCl
levels will range from 0 to 160 ppm (0 to 0.016 percent).
There is a wide range of potential stack gas SO2 emission rates. For
dry APC devices, a worst case (maximum emission) scenario would have no change
in S02 rates across the APC device, and a slight reduction at the stack
monitoring location due only to the affects of dilution air. This worst case
range would therefore be 0 to 1200 ppm. Should dry scrubbing be practiced,
the uncontrolled emission rate given in Table 8 could be reduced as much as
85 percent.
Wet scrubbers can be designed to remove as much SO2 as required. If we
assume that a scrubber installed for HCl control will remove at least 80
percent of the flue gas SC>2> the APC device outlet emissions will total
300 ppm. If we further assume, as before, that this level is diluted by an
additional 20 percent fugitive excess air, the stack gas SC>2 range will be 0
to 240 ppm.
Finally, NOX levels are conservatively assumed not to be affected by
any form of wet or dry scrubbing. Stack gas NOX levels will be reduced only
by the additional 20 percent excess air. Stack gas NOX concentrations for
both dry and wet devices are estimated at 0 to 1600 ppm.
Fluidized-Bed
The estimated stack gas temperature and pressure for fluidized to bed
units is identical to those values proposed for liquid injection and rotary
kiln incinerators. Systems using dry APC devices will have stack temperatures
ranging from 80 to 280°C (175 to 535°F), while those with wet devices will
probably experience temperatures in the 60 to 90°C (140 to 190°F) range.
Stack pressures, regardless of device, will vary from -2.0 to +2.0 inches,
water gauge.
The excess air rate is again assumed to remain essentially unchanged
until the fan. After this point an additional 20 percent excess air rate is
assumed to account for potential leakage into the stack. Resulting stack gas
excess air rate therefore ranges from 30 to 70 percent.
This increased excess air rate will translate into a stack oxygen
concentration of from 5 to 9 percent for all types of systems. Carbon dioxide
concentrations will vary depending on the type of air cleaner employed.
Systems using dry APC devices will experience stack gas CC>2 in the 8 to 12
percent range. Wet devices, with some CC>2 absorption, will have slightly
lower values, varying from 7 to 11 percent.
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As with the other systems, carbon monoxide is assumed not to change
across the APC device. A maximum CO concentration of 50 ppm can be
anticipated in the fluidized bed stack.
The correlation between stack gas moisture levels and type of APC device
utilized is the same for fluidized bed incinerators. Dry cleaning systems
will see their moisture levels essentially unchanged at 5 to 25 percent. Wet
systems will typically demonstrate levels in the 20 to 63.5 percent range,
assuming the stack contains a saturated flue gas. Stack gas moisture contents
will be lower if the gas is not completely saturated or if flue gas reheating
is employed for visible plume dissipation.
The analysis technique described for the pollutants of concern was also
employed to estimate fluidized bed stack gas composition. The extent of
pollutant removal and dilution will remain the same, although the actual
emission rates are different than the other incinerator designs.
Hydrogen chloride in dry systems is estimated to be a maximum of 400 ppm
(0.04 percent). Wet scrubbers, with 99 percent minimum control will produce
maximum stack levels in the 100 ppm range. Accounting for additional dilution
air, this level will be approximately 80 ppm (0.008 percent).
Sulfur dioxide emissions are assumed to be unaffected by dry AFC
devices. The stack gas level of S02 is affected only by additional dilution
air and will, at a maximum, reach 800 ppm. Wet systems will scrub an
approximate 80 percent of the S02 from the flue gas. When the remaining
S02 is further diluted by a 20 percent air leakage rate, the resulting stack
gas S0£ range is 0 to 160 ppm.
Finally, NOX emissions are estimated to be unaffected by any type of
APC control. The stack gas concentration is diluted by infiltration air to a
maximum level of 1200 ppm.
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SECTION 6
CONCLUSIONS
Continuous emission monitors (CMS) that are used to measure the
performance of a hazardous waste incinerator must be equipped to experience a
wide range of environments. Depending on where in the total incineration
system the GEM is placed, it can potentially encounter temperature extremes of
up to 1700°C (3000°F), moisture levels between from 3 to 65 percent and acid
gas levels that may simultaneously reach several thousand parts per million
for each of several different pollutants. In addition, the GEM and its
associated support apparatus must be sufficiently versatile to be adapted to
the hot, confined atmosphere at the combustion zone outlet, as well as to the
exposed sampling location of an exhaust stack. Obtaining representative flue
gas samples from a hazardous waste incinerator presents a difficult and unique
challenge that requires a thorough knowledge of the system and comprehensive
planning for the wide range of conditions that may be experienced.
This report has attempted to define the limits of flue gas conditions
that may be encountered in an incineration system that is combusting Appendix
XIII hazardous waste constituents. This has been a difficult task given the
wide number of variables that can dramatically change the flue gas composition
from one facility to another and from one burn to another at the same
facility. Nonetheless, estimates based on a knowledge of the waste and the
equipment used for incineration and air pollution control have been made, in
order to define "worst case" situations. Continuous emissions monitors that
are designed to withstand these maximum flue gas conditions should be equipped
to measure any combination of intermediate values.
Perhaps the greatest variable in hazardous waste incineration is the
waste itself. Unlike municipal solid waste or sewage sludge, whose
composition, combustion, and emission characteristics are well documented,
Appendix VIII hazardous wastes are relatively unknown. While the chemical
structure of all 375 Appendix VIII substances has been identified,
characteristics such as auto-ignition temperatures, heats of combustion,
time/temperature destruction requirements and incomplete combustion products
have only recently begun to be studied in depth. Moreover, the affect that
blending of various hazardous constituents has on the incinerability of any
individual waste constituent is not well known. Hazardous waste is unlike
municipal solid waste, specific industrial manufacturing waste, municipal
sewage sludge and conventional fossil fuels in that it is not homogeneous.
The 375 hazardous constituents can be blended to form an inexhaustable number
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of potentially incinerable waste streams. These streams in turn can produce
an unlimited combination of pollutant emission concentrations. The task of
quantifying the extremes in these pollutant levels was further hampered by the
general lack of well documented, published test data. The data that is
available was usually associated with a one-of-a-kind research test, and these
results are not necessarily representative of what might occur in the field.
To ensure that the worst case pollutant emission levels were stated in this
study, all judgements concerning emissions were conservative, in that they may
have overstated the maximum possible emission rate. For example, estimates of
5000 ppm for NOX and SOX emissions and a 7 percent HC1 concentration from
liquid injection incinerators may have vastly over-stated the levels that will
ever be seen from these units in actual test conditions. Nevertheless, using
the rationale presented in the body of the report, such levels may potentially
be encountered. To ensure that the GEM is adequately prepared for the
absolute worst case situation, the highest potential pollutant level was used
as a maximum value.
A similiar ambiguity existed for hazardous waste incinerators. Hazardous
waste incineration is, itself, not new. Through mid-1981, up to 342 hazardous
waste incinerators were in active service. " All but two of these units are
employed at specific industrial sites. The technologies employed by these
incinerators was, for the most part, also not new, with virtually two thirds
of active hazardous waste incinerators using the common liquid injection
design. The basic design and operating principles of these incinerators are
well documented and have been presented in Section 3. The key variable with
incinerators is, however, actual operation. From the limited test data that
is available, it appears that incinerators are not always run as designed.
They may be operated with higher temperatures or excess air levels than
required to ensure complete waste destruction, or they may be run at less than
optimum capacity, and this would change such parameters as excess air rates
and oxygen and carbon dioxide concentrations. In arriving at the parameter
estimates presented in Tables 7 through 9, basic assumptions on incinerator
operation were assumed; that it operated at or near peak thermal and
combustion efficiency, that it was well monitored, maintained and run, and
that operating values were close to design values. Individual hazardous waste
incinerators may be encountered, whose flue gas parameters fall outside those
stated in Tables 7 through 9. However, based on currently available data,
such cases are thought to be the exception and not the rule.
Section 4 presented the principal air pollution control device that may
be used in conjunction with a hazardous waste incinerator. At least one APC
device is required with most incinerators, but a number of installations
(especially commercial incinerators), require two devices, in series with each
other. The selection of any device will be based on applicable emission
regulations, the type and variability of the wastes burned and the type of
incinerator employed. The most commonly used devices include the venturi
scrubbers and packed tower scrubbers. The former is particularly effective
with high particulate loadings in the exhaust gases, and the latter is most
effective in removing soluble acid gases providing the particulate loading is
low. Fabric filters have temperature limitations and do nothing to gases.
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ESPs are very effective for particulate removal but have a high capital
cost.^ Due to these restrictions, fabric filters and ESPs were not
discussed in depth in thia report. Nevertheless, if these "dry" devices are
employed, the characteristics of the flue gas stream will change dramatically,
so a distinction had to be made between "wet" and "dry" air pollution
control. Finally, heat recovery devices are becoming an integral part of most
new incineration systems,'' so a further distinction was required to
differentiate between gas streams that were cooled by heat recovery and those
that used quench chambers to lower gas temperature by water cooling.
The focal point of the report is the definition of actual GEM parameters
for the three monitoring zones of interest, which is reported in Section 5.
The most extreme conditions for all three incinerator designs will be found in
the combuston zone. Temperatures are at an extreme in this zone for all
incinerators and maximum concentrations of all pollutants will be found here.
This high temperature/high pollutant (especially acid gas) combination makes
sampling a particularly difficult task, as the sampling probe must be shielded
from the corrosive properties of the acid gases while the probe as well as the
gas stream must be cooled and conditioned. Liquid injection incinerators
present the greatest sampling challenge, as the range of potential
temperatures, pressures and pollutant levels are the highest of all three
incinerator designs. By comparison, fluidized bed incinerators have the least
severe conditions, with lower temperature, air flow and pollutant emissions.
Due to the difficulty of sampling the actual combustion zone of a rotary kiln,
these incinerators must have combustion samples obtained downstream of the
associated afterburner.
The second sampling zone is located after the flue gas cooling device but
before the air pollution control. This site can be characterized by the
uniform temperatures that will follow either heat recovery or water quenching,
regardless of the type of incinerator used. Systems employing heat recovery
will have higher temperatures at this point in order to avoid potential acid
gas condensation on internal heat exchanger surfaces. Some systems may employ
both heat recovery and water quenching in series. For these systems, the
water quenching parameter data will apply. In addition, certain incinerator
systems that employ venturi scrubbers may utilize neither form of heat
recovery. Flue gas temperatures for these systems may approach 1090°C
(2600°F) at this monitoring location. Such installations are thought to be
atypical, and were therefore not included in setting standard temperature
ranges.
The pressure variation at this second monitoring site will be the
greatest of any of the locations, and will depend upon the pressure drop of
the cooling device. All other GEM parameters at this location, with the
exception of moisture content, will be the same as those of the combustion
zone. Flue gas moisture content will depend on whether a dry or wet cooling
device is used. For dry devices, there will be no change in moisture levels.
For water cooling, moisture levels may represent as much as 65 percent of the
total flue gas volume. Again, individual incineration facility practices will
dictate exact moisture levels.
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The final GEM sampling site, will be located after the APC device, usually
in the exhaust stack. Here, flue gas temperatures will be at their lowest
level of the entire system, pressures will be within a fairly narrow range,
and excess air rates will be at their greatest. The moisture level of the gas
stream may be equal to or somewhat lower than the pre-APC device location.
The carbon monoxide content of the gas stream will also be at the lowest level
of any point in the entire system. Concentrations of acid gases can vary
considerably, depending on what, if any, emission limitation must be met. The
establishment of ranges for SC^ HC1 and NOX at this final monitoring
point was the most difficult part of this assignment, as regulations in this
area are still under development by many states. As a result stack emissions,
particularly for SC>2 and NOX, can run the gamut from essentially
uncontrolled to control down to one-tenth or one one-hundredth of uncontrolled
levels. Consequently, the estimates presented in Table 9 for acid gas levels
could be as much as one or two orders of magnitude higher than what might be
observed in the field. The range of possible variables that play a part in
estimating emission rates as well as the desire to define absolute worst case
emission rates precludes defining the range of emission rates any tighter.
In summary, this report has attempted to define ranges of values for the
commonly encountered continuous emission monitor parameters. Due to the
number of potential wastes, the equipment and operating variables that affect
monitoring parameter ranges, and the general lack of comprehensive emission
test data, this effort has had to principally rely on engineering estimates to
define flue gas composition during incineration of Appendix VIII hazardous
waste constituents. As more experience is gained in this field, these
estimates can be further refined to reflect actual operating conditions.
65
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REFERENCES
1. U.S. Environmental Protection Agency, Regulations for Hazardous Waste
Management, 40 CFR Parts 260-265, 267.
2. Bonner, T. A., et al. Engineering Handbook for Hazardous Waste
Incineration, SW-889, U.S. Environmental Protection Agency, Cincinnati,
Ohio, June 1981.
3. Cudahy, J. J., L. Sroka, W. Troxler. Incineration Characteristics of
RCRA Listed Hazardous Wastes. U.S. Environmental Protection Agency,
Office of Research and Development, Cincinnati, Ohio, July 1981.
4. Marks. Standard Handbook for Mechanical Engineers, 7th Edition,
McGraw-Hill, New York, 1976.
5. Axworthy, A. E., et al. Chemistry of Fuel Nitrogen Conversion to NOX
in Combustion. EPA-600/2-76-039, U.S. Environmental Protection Agency,
Research Triangle Park, N.C., February 1976.
6. Kiang, Y. S., A. A. Metry, Hazardous Waste Processing Technology. Ann
Arbor Science, Ann Arbor, Michigan, 1982.
7. Waste Disposal by Thermal Oxidation. John Zink Company, Process Systems
Division, Tulsa, Oklahoma, 1981.
8. Environmental Protection Agency, Regulations for Owners and Operators of
Permitted Hazardous Waste Facilities, 40 CFR Part 265, Subpart 0 -
Incinerators.
9. Draft Permit Writers Guidelines for Hazardous Waste Incineration. U.S.
Environmental Protection Agency, Cincinnati, Ohio, April 1980.
10. Oppelt, E. Timothy. Thermal Destruction Options for Controlling
Hazardous Wastes. Civil Engineering, September 1981, pp. 72-75.
11. Santoleri, Joseph J. Chlorinated Hydrocarbon Waste Recovery and
Pollution Abatement. Proceedings of 1972 National Incinerator
Conference, New York, N.Y., June 4-7, 1972, pp. 66-74.
66
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12. Brady, J. D. Scrubbing and Filtration Systems to Control Gaseous and
Particulate Emissions from Hazardous Waste Incinerators. Paper presented
at the A.P.C.A., Mid-Atlantic States Section Conference on "The Burning
Issue of Disposing of Hazardous Wastes by Thermal Incineration," Newark,
N.J., April 29-30, 1982.
13. Wall, C. J., J. T. Graves, E. J. Roberts. How to Burn Salty Sludges.
Chemical Engineering, April 14, 1975, pp. 77-82.
14. Morth, A. J. Industrial Incineration Experience. Paper presented at the
A.P.C.A., Mid-Atlantic States Section Conference on "The Burning Issue of
Disposing of Hazardous Wastes by Thermal Incineration," Newark, N.J.,
April 29-30, 1982.
15. Environmental Protection Agency, 40 CFR Part 761. Polychlorinated
Biphenyls (PCBs) Manufacturing, Processing, Distribution in Commerce, and
Use Prohibitions.
16. Frankel, I., N. Sanders, and G. Vogel. Profile of the Hazardous Waste
Incinerator Manufacturing Industry. Draft Report prepared by the Mitre
Corportion for the U.S. Environmental Protection Agency, Cincinnati,
Ohio, August 1981.
17. Hitchcock, D. A. Solid Waste Disposal: Incineration. Chemical
Engineering, May 21, 1979, pp. 185-194.
18. Destroying Chemical Wastes in Commercial Scale Incinerators. Final
Report, Phase II, prepared by TRW, Inc., for the U.S. Environmental
Protection Agency, Washington, B.C., November 1977.
19. Ackerman, D. G., et al. Guidelines for the Disposal of PCBs and PCB
Items by Thermal Destruction. Draft Final Report prepared by TRW, Inc.
for U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina, May 1980.
20. Freeman, H. M., et al. Evaluation of Selected Innovative Thermal
Hazardous Waste Destruction Processes. Paper presented at the A.P.C.A.,
Mid-Atlantic States Section Conference on "The Burning Issue of Disposing
of Hazardous Wastes by Thermal Incineration," Newark, N.J., April 29-30,
1982.
21. Esposito, R. G. Fluidized Bed Incineration of Hazardous Liquids and
Solids. Paper presented at the A.P.C.A., Mid-Atlantic States Section
Conference on "The Burning Issue of Disposing of Hazardous Wastes by
Thermal Incineration," Newark, N.J., April 29-30, 1982.
22. Lewis, C. R., et al. Incineration of Industrial Wastes. Chemical
Engineering Deskbook Issue, October 18, 1975.
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23. Ackerman, D. G., et al. At Sea Incineration of Herbicide Orange Onboard
the M/T Vulcanus. EPA-600/2-78-086. U.S. Environmental Protection
Agency, Research Triangle Park, N.C., April 1978.
24. Guidelines for Industrial Boiler Performance Improvement.
EPA-600/8-77-003a. Federal Energy Administration, Washington, D.C., U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina,
January 1977.
25. Ferguson, F. L., et al. Determination of Incinerator Operating
Conditions Necessary for Safe Disposal of Pesticides. EPA-600/2-75-041.
U.S. Environmental Protection Agency, Cincinnati, Ohio, December 1975.
26. Wastler, T. A., et al. Disposal of Organochlorine Wastes by Incineration
at Sea. U.S. Department of Commerce, Maritime Administration for U.S.
Environmental Protection Agency, EPA-430/9-75-014, July 1975.
27. Telecon. Rakesh Gupta, Trane Thermal Company, Conshohocken, PA, with R.
Mclnnes, GCA/Technology Division, June 25, 1982.
28. Pershing, D. W., and J. 0. L. Wendt. Pulverized Coal Combustion: The
Influence of Flame Temperature and Coal Composition on Thermal and Fuel
NOX. Sixteenth Symposium (International) on Combustion. The
Combustion Institute, 1976.
29. Gregory, R. C. Design of Hazardous Waste Incinerators. Chemical
Engineering Progress, April 1981, pp. 43-47.
30. Ottinger, R. S., et al. Recommended Methods of Reduction,
Neutralization, Recovery, or Disposal of Hazardous Waste. Volume III,
Disposal Process Descriptions - Ultimate Disposal, Incineration, and
Pyrolysis. EPA-670/2-73-053c. U.S. Environmental Protection Agency,
Cincinnati, Ohio, August 1973.
31. Babcock and Wilcox. Useful Tables for Engineers and Steam Users.
Eleventh Edition, 1969.
32. Shen, T. T., M. Chen, and J. Lauber. Incineration of Toxic Chemical
Wastes. Pollution Engineering, October 1978, pp. 45-50.
33. Strauss, W. Industrial Gas Cleaning. 2nd Edition. Pergamon Press, New
York, 1975.
34. Dennis, R., D. R. Roeck, and N. F. Surprenant. Status Report on Control
of Particulate Emissions from Coal Fired Utility Boilers. GCA/Technology
Division for Utility Air Regulations Group, May 1978.
35. Kaplan, N., and M. A. Maxwell. Removal of SO2 From Industrial Waste
Gases. Chemical Engineering Deskbook Issue, October 17, 1977, pp.
127-135.
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36. Fabian, H. W., P. Reher, and M. Schoen. How Bayer Incinerates Wastes.
Hydrocarbon Processing, April 1979, pp. 183-191.
37. Seaverns, G. A., and D. R. J. Roy. Air Pollution Control Technology for
Hazardous Wastes Incineration. Paper presented at the A.P.O.A.,
Mid-Atlantic States Section Conference on "The Burning Issue of Disposing
of Hazardous Wastes by Thermal Incineration," Newark, N.J., April 29-30,
1982.
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TECHNICAL REPORT DATA
(Please read Inunctions on the reverse before completing)
ERA-60°0 / 8- 84- Ollb
2.
3. RECIPIENT'S ACCESSION'NO.
4. TITLE AND SUBTITLE Feasibility Study for Adapting Present
Combustion Source Continuous Monitoring Systems to
Hazardous Waste Incinerators; Vol. 2. Review and
Estimation of Incineration Test Conditions
6. REPORT DATE
March 1984
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert Mclnnes, Edward F. Peduto, John W.
Podlenski, Frank Abell, and Stephen Gronberg
8. PERFORMING ORGANIZATION REPORT NO.
GCA-TR-82-60-G(2)
9. PERFORMING ORGANIZATION NAME AND ADDRESS
GCA/Technology Division
213 Burlington Road
Bedford, Massachusetts 01730
1O. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-3168, Task 55
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD CO
Task Final; 10/81 - 9/82
VERED
14. SPONSORING AGENCY CODE
EPA/600/13
is. SUPPLEMENTARY NOTES lERL-RTP project officer is Merril
919/541-2559. Volume 1 is an adaptability study and
D. Jackson, Mail Drop 62,
-1- document.
guidelines
i6. ABSTRACT
repOrt gives results of an adaptability study of commercially available
sample conditioning and measurement systems, in the form of a guidelines document
to be used by EPA and industry personnel. As part of EPA- sponsored research pro-
grams to investigate sampling and analysis methods for hazardous waste inciner-
ation (focused on adapting existing methods for identifying and quantifying constit-
uents listed in 40 CFR 261), the adaptability of existing continuous emission moni-
toring systems (GEMS) involves such measurement categories as SO2, SOS, NOx,
CO, CO2, O2, HC1, and organic materials. Study results indicate that commercially
available extractive continuous monitors can be adapted to incinerators through pro-
per sample conditioning. Available CEMS provide the ranges and sensitivities
needed to accurately measure concentrations of the organic and inorganic compo-
nents of interest.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Croup
Pollution
Monitors
Incinerators
Wastes
Toxicity
Measurement
Samples
Treatment
Pollution Control
Stationary Sources
Continuous Monitors
Hazardous Waste
Sample Conditioning
13B
14G
06T
14B
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
75
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
70
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