EPA-453/R-94-044a
Medical Waste Incinerators-Background Information for Proposed
Standards and Guidelines:
Control Technology Performance
Report for New and
Existing Facilities
July 1994
U. S. Environmental Protection Agency
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina
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DISCLAIMER
This report is issued by the Emission Standards Division,
Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency. It presents technical data of interest to a
limited number of readers. Mention of trade names and commercial
products is not intended to constitute endorsement or
recommendation for use. . Copies of this report are available free
of charge to Federal employees, current contractors and grantees,
and nonprofit organizations--as supplies permit--from the Library
Services Office (MD-35), U. S. Environmental Protection Agency,
Research Triangle Park, North Carolina 27711 ([919] 541-2777) or,
for a nominal fee, from the National Technical Information
Service, 5285 Port Royal Road, Springfield, Virginia 22161
( [703] 487-4650) .
iii
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TABLE OF CONTENTS
1 0 INTRODUCTION
1
2
n
911 The Chemical Reactions ....... 4
212 The Combustion Process ......... 6
2'2 ^raene'rafApproacAes to ^tion
2.2.2 ipecific Coitroi Practices ....... 10
3 0 ADD-ON AIR POLLUTION CONTROL SYSTEMS .... • • • ; £
3'1 f I r^ffc^ing Meciani-s '. '. ---- ; ;
312 Venturi Scrubbers ........ 49
o'-i'i Packed-Bed Scrubbers ......... 55
'•ll o?ner Wet -Scrubbing Systems ...... |4
32 SIT Ss^^issf-^ss' : ; ;i
3 '.2 '.3 Favors Affecting Performance . . . - - ^
•3, -3, DRY SCRUBBERS ..... . • : : * ..... . . 74
331 Dry Scrubbing Principles ........ 77
3*3*2 Dry Sorbent Injection ......... 83
3. 3 ".3 Spray Dryer Absorbers ..... • • •
89
4 o PERFORMANCE OF EMISSION CONTROL MEASURES . . ; - ^
A •} TEST PROGRAM SUMMARY . • • • , • . •
I ? 1 Facility and Test Condition ^ 90
Descriptions .......... _ 96
412 Test Data Summary . • ........ 10o
4.2 I CUSSION OF THE ^RESULTS ^ • •
SaS^ •
4 2., a Baici M«i ..
4*2.5 Metals Partitioning ........ ^ ^ 130
^S/lMllsro^CONTRoL LE^Ls" '. '. '. - - 1«
431 Particulate Matter ........ ^ 151
4* 3*. 2 Carbon Monoxide .......... ' ^ 155
4 3.3 Dioxins and Furans ........ ^ ^ 161
4 3.4 Hydrogen Chloride ........ ^ 16g
4.3.5 Sulfur Dioxide .......... "... 169
4.3.6 Lead ............... ... 173
4.3.7 Cadmium ............. ... 176
4.3.8 Mercury .............. . . • 180
43.9 Nitrogen Oxides ........
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TABLE OF CONTENTS
5.0 REFERENCES
Page
185
APPENDIX A.
APPENDIX B.
APPENDIX C.
APPENDIX D.
SUMMARY OF TEST PROGRAM OPERATING DATA
TEST PROGRAM EMISSION DATA SUMMARY
GRAPHS OF POST-COMBUSTION EMISSION DATA
GRAPHS OF POST-APCS EMISSION CONCENTRATIONS
VI
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LIST OF FIGURES
Figure 1. Relationship of temperature to excess air . .
Figure 2. Impact of temperature and fuel nitrogen on
NO emissions for excess air conditions
(calculated using EER kinetic set)
Figure 3. Theoretical temperature of the products of
combustion calculated from typical municipal
solid waste properties, as a function of
refuse moisture and excess air or oxygen
Figure 4. Impact ion
Figure 5. Diffusion •
Figure 6. Absorption
Figure 7. Simplified venturi scrubber configuration .
Figure 8. Schematic of wetted-approach venturi
scrubber
Figure 9. Schematic of wetted-approach, variable
throat venturi scrubber
Figure 10. Venturi scrubber illustrating the flooded
(wetted) elbow and exhaust gases passing to
a cyclonic separator
Figure 11. Venturi scrubber collection efficiency
versus differential pressure
Figure 12. Typical medical waste incinerator exhaust
gas particle size distribution
Figure 13. Schematic of countercurrent packed-bed
scrubber
Figure 14. Schematic of Rotary Atomizing™ scrubber on
a MWI
Figure 15. Schematic of rotary atomizer module ....
Figure 16. Schematic of an ionizing wet scrubber™ . .
Figure 17. The Hydro-Sonic® family of wet scrubbers .
Figure 18. Schematic of a pulse-jet baghouse
Page,
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18
33
34
35
37
39
40
41
44
45
51
57
59
61
63
67
vii
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LIST OF FIGURES (continued)
Page
Figure 19. Mechanisms of adsorption 75
Figure 20. Schematic of dry sorbent injection system . . 78
Figure 21. Schematic of spray dryer absorber system . . 85
Figure 22. Effect of waste type at Facility A on
post-combust ion Hg emissions 102
Figure 23. Effect on waste type on Hg emissions for all
intermittent/continuous MWI's 103
Figure 24. Effect of waste type at Facility A on
post-combustion HCl emissions 105
Figure 25. Relationship between CDD/CDF and CO
emissions 110
Figure 26. Relationship between CDD/CDF and PM
emissions 110
Figure 27. Effect of secondary/tertiary chamber
temperature and residence time on CDD/CDF
emissions 113
Figure 28. Effect of secondary/tertiary chamber
temperature and residence time on CO
emissions 114
Figure 29. Effect of secondary/tertiary chamber
temperature and residence time on PM
emissions 115
Figure 30. 24-hour real time CO and THC
concentrations--Facility A, test
condition 2, run number 2 122
Figure 31. 24-hour real time CO and THC
concentrations--Facility J, run numbers 5
and 6 122
Figure 32. 24-hour temperature plot--Facility A,
test condition 2, run number 2 ....... 123
Figure 33. 24-hour temperature plot--Facility J,
run numbers 5 and 6 123
Vlll
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LIST OF FIGURES (continued)
Figure 34.
Figure 35.
Figure 36.
Figure 37.
Figure 38.
Figure 39.
Figure 40.
Figure 41.
Figure 42 .
Figure 43 .
Figure 44.
Figure 45.
Figure 46 .
Figure 47.
Cooldown period- -Facility A, test
condition 2, run number 2
Cooldown period- -Facility J, run numbers 5
and 6
Plot of HC1 removal efficiency versus
stoichiometric ratio for Facility A .....
PM emissions for continuous, intermittent,
and batch MWI's with combustion controls . .
PM emissions for uncontrolled pathological
MWI ' S
PM emissions for continuous, intermittent,
batch, and pathological MWI's with add-on
controls
CO emissions for continuous, intermittent,
and batch MWI's with combustion controls . .
CO emissions for uncontrolled pathological
MWI's
CDD/CDF emissions for continuous,
intermittent, and batch MWI's with
combustion controls
CDD/CDF emissions for uncontrolled
pathological MWI's
CDD/CDF emissions for continuous,
. intermittent, batch, and pathological
MWI's with add-on controls
HC1 emissions for continuous, intermittent,
and batch MWI's with combustion controls . .
HC1 emissions for uncontrolled pathological
MWI'S " " * /
HC1 emissions for continuous, intermittent,
batch, and pathological MWI's with add-on
rontrols
Paae
125
125
136
147
149
152
153
154
1 CC
J.DD
158
T C Q
IbS
163
164
165
Figure 48
SO, emissions for continuous, intermittent,
and batch MWI's with combustion controls
167
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LIST OF FIGURES (continued)
Figure 49.
Figure 50.
Figure 51.
Figure 52.
Figure 53.
Figure 54.
Figure 55.
Figure 56.
Figure 57.
Figure 58.
Figure 59.
Figure 60.
S02 emissions for uncontrolled pathological
MWI's
Pb emissions for continuous, intermittent,
and batch MWI's with combustion controls
.Pb emissions for uncontrolled pathological
MWI's
Pb emissions for continuous, intermittent,
batch, and pathological MWI's with add-on
controls
Cd emissions for continuous, intermittent,
and batch MWI's with combustion controls
Cd emissions for uncontrolled pathological
MWI's .....
Cd emissions for continuous, intermittent,
batch, and pathological MWI's with add-on
controls
Hg emissions for continuous, intermittent,
and batch MWI's with combustion controls
Hg emissions for uncontrolled pathological
MWI's
Hg emissions for continuous, intermittent,
batch, and pathological MWI's with add-on
controls
NOy emissions for continuous, intermittent,
and batch MWI's with combustion controls
NOX emissions for uncontrolled pathological
MWT's
Page
168
170
171
172
174
175
177
178
179
181
183
184
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LIST OF TABLES
TABLE 1.
TABLE 2.
TABLE 3.
CONDITION
91
98
106
l>U3iJEj •» .
TABLE 5.
TZkRLiE 6
J_ f*± " -1— ' •*— 1 u *
TABLE 7.
TABLE 8.
faHTiP Q
l/^BljEi ^ •
TABLE 10 .
J_ J^JJJJA-* -^- **
TABLE 11.
TABLE 12 .
^^^^j^jij ^** •
TABLE 13.
TABLE 14.
TABLE 15.
TABLE 16.
Tatar .TT. 17 .
S^ssss rss « • •
COMPARISON OF POST -COMBUSTION EMIS^°?S FROM ^
SUMMARY OF BOTTOM ASH AND STACK GAS METALS ^
DISTRIBUTION
PERFORMANCE OF THE VS/PB AND FF/PB AIR
POLLUTION CONTROL SYSTEMS
FACILITY A HC1 PERFORMANCE SUMMARY
SUMMARY OF METAL EFFICIENCIES BY TEST
CONDITIONS AT FACILITY A • •
____. T^/"\T^ *^^JU?
SUMMARY OF CDD/CDF PERFORMANCE DATA FOR THE ^
DI/FF AT FACILITY A
HC1 PERFORMANCE DATA FOR FACILITY M
SUMMARY OF CDD/CDF AND METALS PERFORMANCE
FOR SD/FF SYSTEM
TESTED MWI FACILITIES
COMBUSTION CONTROL DATA VS. MWI TYPES ....
120
127
129
131
134
137
138
140
141
143
144
146
151
155
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TABLE 18.
TABLE 19.
TABLE 20.
TABLE 21.
TABLE 22.
TABLE 23.
LIST OF TABLES (continued)
HC1 EMISSION LIMITS FOR CONTINUOUS
INTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
S02 EMISSION LIMITS FOR CONTINUOUS
INTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
Pb EMISSION LIMITS FOR CONTINUOUS
INTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
Cd EMISSION LIMITS FOR CONTINUOUS,
INTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
Hg EMISSION LIMITS FOR CONTINUOUS
INTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
x EMISSION LIMITS FOR CONTINUOUS
INTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
Page
162
166
169
173
176
182
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1.0 INTRODUCTION
The main objectives of this report are to describe the
various emission control techniques used to control emissions
from medical waste incinerators (MWI's), to summarize the
emission test data generated during a comprehensive emission test
program, and to provide an emission test data analysis that
quantifies the performance of these techniques. Two general
types of emission control techniques are described: combustion
controls and add-on air pollution control systems (APCS's).
Combustion controls refer to the control of the combustion
process and the emission-generating mechanisms through proper
design, operation, and maintenance to minimize the generation of
emissions. Add-on APCS's control or remove pollutants from the
exhaust gas stream after the gas stream exits the MWI system.
This document is one of a series of reports written to provide
background information used to develop emission standards and
guidelines for MWI's under Section 129 of the Clean Air Act.
This report presents technical information on the emission
control techniques available to control emissions from MWI's.
Section 2.0 first describes the general approaches to combustion
controls and subsequently describes specific designs and/or
operational features that are employed to control the combustion
process. Section 3.0 describes the add-on APCS's. Section 3.1
describes wet scrubbers including the venturi and packed-bed
scrubbers in detail and briefly describes other types of wet
scrubbers including the Rotary Atomizing™ scrubber. Ionizing Wet
Scrubber™, the collision scrubber, and the Hydrosonic® scrubber.
Section 3.2 describes fabric filters. Section 3.3 describes dry
scrubbers including dry sorbent injection and spray dryer
systems. Finally, Section 4.0 summarizes available emission test
data and presents a test data analysis that quantifies the
performance of APCS's (venturi/packed-bed scrubber, fabric
filter/packed-bed scrubber, dry sorbent injection/fabric filter,
spray dryer absorber/fabric filter), and three combustion
controls (increased secondary chamber residence time, increased
secondary chamber temperature, and proper charging procedures).
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2.0 COMBUSTION: THEORY AND CONTROL
The emissions from an MWI are influenced strongly by the
combustion process conditions. Consequently, combustion control
can be an important element of MWI emission control measures.
This section describes the MWI combustion process and discusses
methods that are being used to control that process. Section 2.1
provides a brief overview of combustion theory and summarizes how
the process characteristics affect emissions. Section 2.2
describes general approaches to combustion control and describes
specific control practices that are typically used.
2.1 COMBUSTION THEORY
Combustion is defined generically as a chemical oxidation
reaction characterized by the evolution of energy as light and
heat. The medical waste combustion process is characterized by a
complex combination of chemical reactions that involve the rapid
oxidation of organic substances in the waste and auxiliary fuels.
The goal of the process is to achieve complete combustion of the
organic material, while minimizing the formation and release of
undesirable pollutants.
This section presents a brief overview of the combustion
process as it relates to medical waste incineration and describes
the key physical and chemical phenomena that occur in combustion
systems. It also identifies the key operating parameters and
discusses their effect on the combustion process.
2.1.1 The Chemical Reactions
Because medical waste is a heterogeneous mixture of general
refuse, pathological wastes, plastics, and laboratory wastes, the
specific chemical composition is unknown and varies with time.
However, the process can be described reasonably well by making
some simplifying assumptions about the key chemical reactions.
The organic portion of medical waste consists primarily of
carbon (C), hydrogen (H), and oxygen (0), with other elements
such as sulfur (S), chlorine (Cl), nitrogen (N), and a variety of
metals being found to a lesser degree. Key combustion reactions
involve these major waste constituents and the 02 in the
combustion air.
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The simplified equilibrium reactions that characterize the
MWT process are:
C + .0'
C02 + heat
2 H
02 -» 2 H20 + heat
1.
2.
3. H + Cl •* HC1 + heat
4. S + 02 -» S02 + heat
For equation 1, carbon monoxide (GO) also is formed if there
is incomplete combustion. For equation 3, the available
thermodynamic equilibrium data and bench- scale test data indicate
that organic chlorine reacts almost completely to form hydrogen
chloride (HC1) with small quantities of elemental chlorine (C12)
also produced. However, unless the H:C1 ratio in the feed is
very low, and external hydrogen sources (e.g., water vapor) are
unavailable, almost no C12 is formed.1 For equation 4, the
organic sulfur is oxidized during the combustion process to form
sulfur dioxide (S02) . Because HC1 is a stronger acid than S02,
it will react more quickly with available alkaline compounds.
Some S02 may react with available alkaline compounds; however,
the amount of S02 involved in such reactions is expected to be
negligible due to the high HC1 content of the flue gas.
Consequently, essentially all of the organic sulfur in the waste
will leave the combustion chamber as vapor phase S02 .
While these simplified reactions identify the major
combustion products, they do not present a complete picture of
the combustion process. Because of incomplete combustion,
dissociation, and the formation of thermal and fuel nitrogen
oxides (NOX) , the MWI exhaust gases will also contain trace
amounts of CO, NOX, methane (CH4) , C12, and a wide range of
organic compounds. Also, volatilization of inorganic compounds
or entrainment of inorganic compounds in the combustion gases
contaminate the exhaust gases with particulate matter (PM) ,
including metals. A major goal of combustion controls is to
minimize concentrations of compounds other than those identified
in Equations 1-4 to levels as low as possible.
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2.1.2 The Combustion Process
The primary objective of the MWI combustion process is the
complete combustion of all organic material in the waste feed.
As described in some detail in Section 2.2, MWI manufacturers and
operators use a variety of specific design and operating
techniques to achieve this goal. Despite this range of
techniques, the basic combustion process and the factors that
determine the ability of the process to achieve complete
combustion are reasonably consistent. As a background for the
more detailed discussion in Section 2.2, the paragraphs below
provide a brief description of the typical MWI process and
identify key factors that affect performance.
The basic MWI design typical of most newer systems is
comprised of two, or possibly three chambers which are referred
to as the primary, secondary, and tertiary chambers. Medical
waste is fed into the primary chamber of these multiple-chamber
units. This medical waste comprises a mixture of organic
material (including volatile organics and fixed carbon),
inorganic material (including metal compounds) , and water. As
this waste enters the primary chamber, it is exposed to a high-
temperature heat source (either an ignition burner or the burning
waste bed) and to combustion air. Key events that occur in the
primary chamber are:
1. Moisture in the waste is evaporated from the waste and
the water vapor temperature is raised to the temperature of the
primary chamber exhaust gases;
2. Volatile organic materials in the waste are released and
some amount of vapor-phase combustion occurs above the waste bed;
3. Fixed carbon is burned via surface oxidation reactions
in the waste bed; and
4. Inorganic materials (particularly metals) are
partitioned as entrained solids in the exhaust gas, vapors in the
exhaust gas, and solid materials in the ash.
In most MWI systems, the combustion air supplied to the
primary chamber is insufficient to complete the reactions
described in Section 2.1.1. Consequently, a fuel-rich, exhaust
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gas stream passes from the primary to the secondary chamber.
Additional combustion air is supplied to the secondary chamber
and the combustion reactions are carried towards completion.
How well this basic process achieves the goal of complete
organic combustion with minimal release of undesirable pollutants
is determined by three key factors that influence the combustion
process. In simplest terms, these factors are usually referred
to as time, temperature, and turbulence (or mixing). The
combustion reactions described in Section 2.1.1 are equilibrium
reactions. The degree to which these reactions move toward
completion is a function of reactant availability, reaction rate,
and time over which conditions are appropriate for the reaction
to occur. The reaction rates for all combustion reactions are
temperature dependent. The temperature at the point of
combustion must be sufficiently high to initiate the reaction,
and the degree of reaction completion depends on the time/
temperature envelop to which the reactants are exposed. The key
combustion reactions are oxidation reactions. Consequently,
oxygen must be in close contact with the material being combusted
for the reactions to proceed quickly. Turbulence is required to
expose unburned material (in both the waste bed and in the
secondary chamber) to the available oxygen in the incoming air.
Without waste-bed turbulence, much of the unburned organic
material (either volatile or fixed carbon) will be insulated
under layers of ash and will not have sufficient oxygen available
to complete the combustion process. The mixing created by
turbulence in the waste bed ensures that all combustible
materials contact the supply of oxygen at some point during the
burning cycle. Turbulence in the secondary chamber ensures that
volatiles and other unburned material are adequately mixed with
combustion air (oxygen) to complete the combustion process begun
in the primary chamber. Adequate secondary chamber temperature
and gas-residence time are also required to complete combustion.
Most combustion control measures described in Section 2.2 are
related to time, temperature, and turbulence.
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One other relationship that is an important prerequisite to
understanding combustion controls is the relationship between
combustion air and temperature. The stoichiometric amount of
combustion air is the quantity of air needed to provide exactly
the theoretical amount of oxygen for complete combustion of
carbon and hydrogen in the waste. Theoretically, 100 percent
stoichiometric air coincides with the condition of maximum
temperature (>1650°C [3000°F]) in the chamber. A graphical
representation of the relationship between combustion temperature
and excess air level is shown in Figure 1. As the amount of
combustion air is increased above the stoichiometric point
(excess air), the combustion temperature is lowered because
energy is used to heat the combustion air from ambient
temperature to the combustion chamber temperature. The greater
the volume of the excess air, the greater the "heat loss" due to
raising the air temperature. As the amount of excess air is
decreased, the combustion temperature increases until it becomes
maximum at the stoichiometric point. Below the stoichiometric
point, as the amount of combustion air is decreased, the
temperature decreases because complete combustion has not
occurred. Because the complete combustion reaction (which is
exothermic) has not occurred, the maximum heat is not generated.
Typically, the primary chamber of an MWI is operated in the
substoichiometric region of the curve, while the secondary
chamber is operated in the excess air region.
2.2 COMBUSTION CONTROL
Combustion controls are defined as any design features or
operating practices that are used by MWI manufacturers and
operators to reduce or limit the quantities of undesirable
pollutants emitted with the MWI exhaust gases and to maximize the
destruction, or burnout, of organic material in the solids bed.
In addition to enhancing the quality of gaseous exhausts and
solids discharge, the control measures are designed to minimize
the operation and maintenance costs of the incineration system.
These goals are often compatible in that the well-controlled
combustion conditions that lead to low emission levels and good
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TEMPERATURE
MAXIMUM
TEMPERATURE
DEFICIENT AIR
EXCESS AIR
PERCENT EXCESS AIR
Figure l. Relationship of temperature to excess air.-
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ash quality' also tend to limit damage to the MWI system, thereby
promoting lower operation and maintenance costs.
The remainder of this section discusses the combustion
control mechanisms that have been implemented by different
manufacturers and operators to control emissions from MWI's. The
discussion is divided into three parts. The first provides a
general overview of the different combustion control approaches
that have been used. The second describes specific control
practices and presents the available information on the
effectiveness of these practices in controlling all pollutants of
interest that are emitted from MWI's. The final subsection
provides a brief overview of how these different specific control
practices are related.
2.2.1 General Approaches to Combustion Control
Each MWI manufacturer has developed a package of features in
its design that is aimed at controlling air emissions and ash
quality. The mixture of controls varies among manufacturers,
making each combustion system unique in its approach to
combustion control. While each system is unique and a wide
variety of specific practices are used, all of the systems
comprise some combination of three general approaches:
(1) controlling the rate of primary chamber chemical reactions,
thereby controlling the release rate of volatile organics and the
degree of ash burnout; (2) controlling waste bed turbulence,
thereby limiting entrainment of particles from the waste bed; and
(3) controlling secondary chamber combustion conditions, thereby
promoting the complete combustion of volatile organic material.
These general approaches are implemented by including design or
operating features that control some combination of the following
parameters: temperature of the reactants and reaction products,
residence time of reactants at reaction temperatures, and gas
turbulence and solids mixing of the reactants in the primary and
secondary chambers of the MWI.
When medical waste is charged to the primary chamber and is
exposed to a high-temperature heat source, such as an already
burning waste bed or auxiliary burners, numerous physical/
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chemical reactions occur in and above the waste bed. These
reactions include vaporization of moisture in the waste, the
volatilization of organic material in the waste, both gas-phase
and surface chemical reactions that involve pyrolysis and
oxidation of organic material, volatilization of inorganic
material in the waste, and the entrainment of solid materials in
the combustion gases. Reactions continue in the secondary
chamber for those gases and solid particles released from the
waste bed. By controlling the key parameters of temperature,
residence time, gas turbulence, and solids mixing of the
reactants within each chamber, the rate and level of completeness
of the physical/chemical reactions are also controlled.
Combustion control within an MWI is usually based on
maintaining temperatures in both chambers within specified limits
by controlling the combustion air rate to each chamber, the waste
feed rate, and the auxiliary fuel burner operation. Limiting
combustion air in the primary chamber to below stoichiometric
conditions prevents rapid combustion, decreases the temperature,
and allows a quiescent condition within the primary chamber that
minimizes entrainment of PM. In the secondary chamber, however,
high temperatures can be maintained in a turbulent condition with
excess air (i.e., greater than stoichiometric levels) to ensure
complete combustion of organics in the gases emitted from the
primary chamber.
Combustion controls are generally aimed at reducing CO and
organic emissions and limiting PM and metals emissions.
Generally, these combustion control measures have little or no
effect on emissions of HC1 and S02- In both cases, most of the
chlorine and sulfur will be converted to HC1 and S02 under the
entire range of combustion conditions which normally occur in an
MWI.
There are varied degrees of combustion control for MWI's,
depending not only on the manufacturer, but also on the type and
size of the incinerator. Combustion control systems vary from
simple, manually-controlled, manually-fed units to highly
complex, automatically-controlled, automatically-fed, continuous
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units. The" specific combustion control practices used, their
interrelationships, and their effects on the emission levels of
specific pollutants are discussed below.
2.2.2 Specific Control Practices
Manufacturers and operators of MWI's use a variety of
techniques to address the combustion control objectives
identified in Section 2.2.1. The techniques that have been
widely applied to MWI's include feed rate control, control of
combustion air volumetric flow and distribution, temperature
control in the primary and secondary chamber, control of solids
retention time in the primary chamber and gas residence time in
the secondary chamber, enhancement of gas mixing in the secondary
chamber, control of solids mixing in the primary chamber, sizing
and location of combustion air ports in the primary chamber,
primary chamber steam injection, and operator training. The
subsections below describe how each of these techniques is
implemented and present qualitative assessments of the effect of
the different techniques on pollutant emissions.
2.2.2.1 Control of Feed Rate. Each incinerator system is
designed for a particular thermal input rate with the thermal
input coming from the waste feed and, when necessary, auxiliary
fuel burners. Under ideal conditions, the incinerator operates
with a constant thermal input. Under actual conditions, however,
the medical waste feed is a heterogeneous mixture with variable
volatile content, fixed-carbon content, ash content, moisture
content, and heating value. Incinerator operating conditions are
varied to the extent possible with changing waste characteristics
in order to promote controlled combustion and minimize pollutant
emissions. Rates of thermal and volatiles release from the waste
feed are controlled by controlling the combustion air rates in
combination with control of waste feed quantity and frequency.
This section describes waste feed control measures, while the
combustion air control measures are described in Section 2.2.2.2.
The effects of waste feed rates on combustion conditions and
emissions are closely tied to waste feed characteristics.
Increasing the feed rate with low-density, high-heating-value
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wastes (plastics, rubber, paper) results in higher gas-phase and
solid-phase combustion rates, higher temperatures, higher
volatiles release rates, and higher gas velocities in the primary
chamber. Also, the higher.temperature and resulting increase in
volatiles release rates generate gas volumes that are likely to
exceed the excess air capacity and volumetric capacity of the
secondary chamber. All of these effects of increased waste feed
rates raise the potential for high-PM emissions from entrainment,
lower secondary chamber residence times, and the discharge of
incomplete combustion products to the environment. Increasing
the feed rate with high-density, low-heating-value wastes
(fluids, tissue, bones) generally creates lower primary chamber
temperatures due to the heat required to vaporize moisture and
the low amount of heat being released from the waste. With
wastes of this type, auxiliary fuel burners must often be
operated to maintain the temperatures in both chambers. The
large volume of water vapor and the small amount of combustible
gases coming from the waste bed coupled with lower primary
chamber temperatures increase the likelihood of the discharge of
incomplete combustion products.
The methods used to control the feed rate for MWI's differ
between batch-duty units and intermittent- or continuous-duty
units. Batch-duty MWI's are designed to accept a single load of
waste at the beginning of the incineration cycle, and feed rate
control is simply a matter of how much waste is loaded into the
primary chamber at that time. If the waste being charged has a
significantly higher heating value than that specified for design
purposes, the primary chamber must be loaded at less than
volumetric capacity to decrease the thermal input from the batch
charge. These units range in size from 331 to 1,724 kg/batch
(150 to 3,800 Ib/batch) and typically are loaded manually. Some
batch MWI's also have options for charge door lock-out tied to a
preset timer or to the primary chamber temperature to prevent the
operator from opening the door before the cycle is complete.
The intermittent- and continuous-duty MWI's typically have a
mechanical charging device (ram feeder) that permits waste
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charging while the MWI is operating. Some small intermittent
units, however, do not have a mechanical loading device but are
charged manually, and some manufacturers offer a continuous
mechanical charging device (auger feeder) for charging their
continuous-duty MWI's. The ram feeder loading device feeds small
charges of waste material to the primary chamber at regularly
timed intervals. The size of each waste charge is controlled by
the size of the hopper and the amount of waste the operator
places into the hopper. The charging frequency can be controlled
manually or by a preset timer on the control panel. Also, the
charging cycle can be locked out or overridden by a control loop
that responds to temperature in the primary chamber or the
temperatures in both the primary and secondary chambers. To
approach a steady thermal input, manufacturers recommend a
charging procedure consisting of multiple charges at equally
timed intervals. The recommended charge size is 10 to 25 percent
of the rated hourly capacity, charged at 5- to 15-minute
intervals. The charging frequency may then need to be adjusted
to respond to variations in the waste composition.
2.2.2.2 Control of Combustion Air. For most MWI's, the
primary combustion controls are driven by control loops that
maintain the temperatures in the primary and secondary chambers
of the incinerator within specified limits. The control
parameter of greatest importance in maintaining these
temperatures within setpoints is the combustion airflow rate in
each chamber.
The combustion air in the primary chamber is typically
controlled to below stoichiometric amounts. As stated in
Section 2.1.2, limiting the combustion air in the primary chamber
to below stoichiometric conditions (generally 40 to 70 percent of
stoichiometric) limits the combustion rate by limiting the amount
of oxygen available for both solid-phase and gas-phase oxidation
reactions. By limiting these combustion reactions, the heat
release rate to the primary chamber is reduced with a
corresponding decrease in temperature. Also, limiting the
combustion airflow and the resulting combustion rate allows a
12
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quiescent condition to exist within the primary chamber that
limits the entrainment of PM in the combustion gases exiting to
the secondary chamber.
The combustion air in the secondary chamber is typically
controlled to greater than stoichiometric amounts (generally
150 to 250 percent of stoichiometric [i.e., 50 to 150 percent
excess air]). Consequently, the secondary chamber is said to
operate with excess air. Combustion gases are maintained at
higher temperatures in a turbulent condition with excess oxygen
to ensure complete combustion of the volatile organic compounds
and CO emitted from the primary chamber. Because the secondary
chamber temperature is operating in an excess air mode,
increasing the amount of combustion air to the secondary chamber
decreases the secondary chamber temperature.
Controlling the combustion air in an MWI permits a staged
combustion system for minimizing pollutant emissions from the
combustion process. By limiting the combustion air and the
temperature in the primary chamber, the formation of fuel NOX and
thermal NOV and the entrainment of particulate matter are
Jt
limited. Enough combustion airflow is maintained to ensure
minimum temperatures for the destruction of pathogens in the
waste and fixed-carbon burnout in the primary chamber. In the
secondary chamber, the combustion air is controlled at levels
that permit enough excess air for the required temperature, gas
turbulence, and residence time of the combustion gases both to
ensure the destruction of pathogens that have been entrained in .
the primary chamber exhaust and to complete the reaction of
organics in the exhaust gas stream.
The conversion of fuel-bound nitrogen to NOX (fuel NOX)
depends in large part on the local availability of oxygen to
react with the volatile species, the amount of fuel-bound
nitrogen, and the chemical structure of the fuel-bound nitrogen.
Because of the substoichiometrie amount of combustion air in the
primary chamber with the fuel, the formation of fuel NOX is
minimized. Combustion air control affects organics destruction,
metals volatilization, thermal NOX generation, and ash burnout
13
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only through the effects of combustion air on temperature and
turbulence. The effects of temperature and turbulence on these
phenomena are described in subsequent sections.
Combustion air control is usually based on the temperatures
of the primary and secondary chambers. Thermocouples within each
chamber are used to monitor the temperatures continuously; this
information is then used to adjust the combustion air rate to
maintain the desired temperatures. Many manufacturers also use
timers and information about the loading and burndown cycles to
control the combustion air. Some manufacturers have also used
parameters such as gas flow, opacity, and oxygen concentration to
Q
control combustion air, but these mechanisms are not typical.
The level of combustion air control varies from manually
setting the combustion airflow dampers for each chamber to fully
modulating the combustion airflow over the entire operating
range. On some systems, the control settings are actuated by the
feedback from a monitored parameter (e.g., temperature), by a
specified time in a cycle (e.g., charge-door opening), or by a
control timer. The more advanced, elaborate combustion air
control systems offer more control of the temperature and hence
the combustion rate in the incinerator, but they are also more
complicated and more costly. The simple, manually set combustion
airflow dampers are generally set for an average charge of
medical waste with a typical composition. As the waste
composition varies and the combustion of the waste charge
proceeds, the combustion airflow through these dampers remains
constant. Consequently, over the duration of a burn cycle, the
percentage of stoichiometric air varies constantly in both
chambers, resulting in changes in the combustion rate,
temperature, turbulence, residence time, and pollutant emissions.
In contrast, the automatically controlled, fully modulated,
combustion air control systems permit continuous monitoring of
the chamber temperature and the control of the combustion airflow
rate according to that temperature. These changes in the
combustion airflow rate also modulate the combustion rate and
tend to smooth out temperature swings in both the primary and
14
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secondary chambers. The increased stability tends to minimize
the increases in pollutant emissions that can result from these
temperature swings found in less automated mi's.
Many of the newer, automatically controlled systems also
stop the combustion airflow to the primary chamber when the
charging door is opened, thereby compensating for the amount of
combustion air that enters through the charge door with the
charge. Many of these systems also operate with the combustion
airflow damper to the secondary chamber fully open at the time of
charging to ensure .maximum excess air to combust the initial
release of volatiles that accompanies a fresh charge.
2.2.2.3 Prmt-.r-ol of Primary Chamber Temperature. Combustion
control for the primary chamber of an MWI is typically based on
controlling the temperature in that chamber. A thermocouple
within the primary chamber is used to monitor the temperature
continuously. Feedback from the monitoring is then used on some
systems to control the combustion air rate at levels that
maintain a specific setpoint temperature within the chamber.
Control of the incinerator feed rate, use of auxiliary fuel
burners, and water injection are other methods that may be used
to control the primary chamber temperature.
The primary chamber must be operated at a temperature
sufficient to sustain combustion and to combust the fixed carbon
in the waste bed. The temperature in the primary chamber is
maintained by the combustion of the fixed carbon within the waste
bed, the combustion of a portion of the combustible gases in the
primary chamber just above the waste bed, and, when necessary,
auxiliary fuel burners. The typical operating ranges noted in
the literature are 400° to 980°C (750' to 1800«F).2'4'5 The
lower setpoint is needed to maintain fixed-carbon combustion and
volatiles release from the waste bed, while temperatures below
the upper setpoint minimize slagging and refractory damage.
The volatiles release rate and the gas- and solid-phase
combustion rate are temperature dependent. Controlling the
temperature level in the primary chamber also controls the
combustion rate and the volatiles release rate from the waste bed
15
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at the time- of charging. If the temperature in the primary
chamber is not controlled, the resulting rapid volatiles release
immediately increases the volume of combustion gases leaving the
chamber, promotes the entrainment of both organic and inorganic
materials, reduces the gas residence time, and increases the
requirement for combustion air in the secondary chamber. Taken
together, these phenomena are likely.to result in increased PM,
CO, metals, and trace organics emissions.
The formation of NOX from nitrogen in the combustion air
(thermal NOX) is limited in both chambers by limiting the peak
flame temperatures to less than 1649°C (3000°F) , typically
through combustion air control. The formation of thermal NOX is
highly temperature dependent and proceeds rapidly at temperatures
in excess of 1649°C (3000°F) (see Figure 2). The theoretical
flame temperature is the maximum flame temperature attainable
with a stoichiometric amount of air and no heat losses and is
typically in the range of 1649° to 1927°C (3000° to 3500°F) (see
Figure 3). The actual flame temperatures, however, for
substoichiometric and excess air conditions with the typical heat
losses due to radiation, convection, conduction, arid
dissociation, are expected to be in the range of 1260° to 1371°C
(2300° to 2500°F). Temperatures in this range are less conducive
to thermal NOX formation than the peak temperatures associated
with stoichiometric air supply.6'7
Primary chamber temperatures affect both the amount of
metals being volatilized and the amount of metals being entrained
in the exhaust gases leaving the primary chamber. Increasing
primary chamber temperatures shifts the metals partitioning
towards the volatile fraction and the entrained particle fraction
and away from the ash fraction. Further, metals that volatilize
at primary combustion chamber temperatures tend to selectively
condense on small particles in the flue gas, a phenomenon known
as fine particle enrichment. Also, higher primary chamber
temperatures usually occur with conditions that cause increased
particle entrainment (i.e., increased waste bed turbulence,
increased combustion airflow, and increased volatiles release
16
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10,000
1000
100
Q.
Q_
o 10
1.0
0.1
3140 2813
T(°F)
2509 2310
2112 1941
MAX
EXPECT
ED
ADIA-
BATIC
TEMP.
0.5% FUEL N
30% EXCESS AIR
r. 0.5 SEC.
THERMAL NO
FUEL N
0.45 0.50 0.55 0.60 0.65 0.70
103/T(K"1)
Figure 2. Impact of temperature and fuel nitrogen on NOX
emissions for excess air conditions (calculated using
EER kinetic set).
17
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4000
u.
e>
D.
LU
o
Ul
§
o
3000
2000 -
1000 .
Moisture
15%
% Excess Oxygen: 0
10
12 14
50
SA 100
150
200
250
300
Vo Excess Air:
50
100
150
250
Figure 3. Theoretical temperature of the products of
combustion calculated from typical municipal solid
waste properties, as a function of refuse moisture
and excess air or oxygen.
(Reproduced from a paper titled "Minimizing Trace Organic
Emissions from Combustion of MSW by Use of Carbon Monoxide
Monitors" by Floyd Hasselriis presented at the ASME
Solid Waste Processing Division Conference in 1986.)
18
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rates). Hence, the amount of entrainment, volatilization, and
enrichment of metals in the smaller-diameter PM is expected to
increase if primary chamber temperatures are raised.
Typically, the primary chamber temperature is controlled by
controlling the feed rate and the combustion air as described in
previous sections. Other alternatives include using auxiliary
fuel burners and/or water injection. For systems that rely
primarily on airflow control, auxiliary fuel burners may be used
as necessary to maintain a minimum setpoint temperature. The
control of the auxiliary fuel burners varies substantially from
unit to unit. The least complex systems consist of simple on/off
switches that activate the burner or shut it off as setpoints are
reached. More sophisticated systems fully modulate the burners
from low fire to high fire based on the primary chamber
temperature. Some manufacturers also offer a water injection
system for rapidly decreasing primary chamber temperatures that
exceed specific maximum setpoints. These systems are generally
simple on/off switches.
For batch-type MWI's, manufacturers control the temperature
by switching the burners and combustion air between high/low or
g n Q
on/off settings based on a series of timers. '
2.2.2.4 Control of Secondary Chamber Temperature. The key
secondary chamber combustion control parameter for MWI's is
temperature. Typically, a thermocouple is used to monitor the
temperature continuously near the secondary chamber outlet. That
information is then used to modulate the amount of combustion air
supplied to that chamber and, in some cases, to modify primary
chamber operations to control the volatiles release rate.
Because the secondary chamber is operated in an excess-air
condition, increasing temperatures trigger an increase in the
combustion airflow rate to bring temperatures back to the
setpoint. (See Figure 1.) This increased combustion air reduces
the secondary chamber temperature because energy is required to
heat the excess air from ambient to flue-gas temperatures.
The primary function of the secondary chamber is to complete
the combustion process initiated in the primary chamber. This
19
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function is"best accomplished if the secondary chamber is
operated within a specified temperature range. If temperatures
are too low, the gaseous and solid organics may not be completely
destroyed. Consequently, the system may emit excessive levels of
PM, CO, and organic emissions. If the temperatures are too high,
refractory damage may occur, residence time may be decreased, and
auxiliary fuel may be wasted. The limited data on pathogen
destruction indicates that pathogens can be destroyed at the
temperatures achievable in MWI's. Experimental work at the
University of Dayton Research Institute indicates that
temperature is the primary factor that affects the decomposition
of organics and that a threshold temperature exists above which
an organic compound rapidly combusts. The threshold temperature
found for polychlorinated dibenzo-p-dioxin (CDD) and
polychlorinated dibenzofurans (CDF) and potential precursors
(e.g., hexachlorobenzene) is near 930°C (1700°F).7 Thermal NOX
formation is highly temperature dependent but only becomes
significant at temperatures in excess of 1650°C (3000°F). As
stated in Section 2.2.3, thermal NOX formation is limited by
limiting the peak flame temperatures within the secondary chamber
to less than 1650°C (3000°F). Typically, upper setpoint
temperatures in the MWI secondary chamber (about 1200°C [2200°F]
keep flame temperatures below those levels, thereby limiting
thermal NOX formation, and prevent refractory damage. In
summary, a secondary chamber temperature operating range of 980°
to 1200°C (1700° to 2200°F) promotes effective destruction of the
organics and pathogens, conserves auxiliary fuel, prevents
refractory damage, and avoids thermal NOX formation.
The methods used to control the temperature in the secondary
chamber include controlling the feed rate and combustion air (See
Sections 2.2.2.1 and 2.2.2.2) and the use of secondary chamber
auxiliary fuel burners. The temperature in the secondary chamber
is typically controlled by modulating the combustion airflow.
Also, when necessary, the auxiliary fuel burners are operated to
maintain a minimum setpoint temperature. Auxiliary burner
control varies from a single on/off switch driven by the lower
20
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setpoint to' fully modulating burners that range continuously over
low-fire to high-fire in response to secondary chamber
temperature. Also, since instantaneous peaks in the flow of
combustion gases generated in the primary chamber can occur, a
recommended operating practice is to keep the secondary chamber
auxiliary burner on at all times to ensure that the volatile
gases from the primary chamber combust completely during these
peak conditions.11
2.2.2.5 Control of Primary Chamber Retention Time. The
nonvolatile combustible portion of the waste (fixed carbon) is
burned on the primary chamber hearth at high temperatures. The
fixed carbon is burned in surface oxidation reactions. This
solid-phase reaction requires higher temperatures and longer
exposure times than do the gas-phase reactions that occur above
the bed in the primary chamber and continue in the secondary
chamber.
After the volatilization of the waste material in the
primary chamber is complete, sufficient time must be provided for
the remaining fixed carbon combustion in the waste bed to be
completed. For batch and intermittent duty incinerators, there
is typically a burndown cycle that is controlled by a preset
timer and temperature feedback from the primary chamber. During
this cycle, the amount of fixed carbon remaining in the waste
slowly decreases. To combust this remaining fixed carbon, a
preset minimum temperature is maintained for a predetermined time
period. The thermal input needed to maintain temperature during
this time is supplied by fixed-carbon combustion and, when
necessary, auxiliary fuel burners. The desired burndown time is
preset by a timer, and the burndown cycle is initiated either
manually by a switch or through an automatic system that
"initiates" the burndown cycle automatically by restarting the
burndown cycle every time the charge door is opened. In this
automatic system, burndown is tied to the last charge. A typical
burndown period for batch and intermittent units is in the range
of 2 to 4 hours.10'12
21
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For continuous-duty incinerators there is no distinct
burndown period since the waste is continuously moving through
the system. However, during shutdown, some continuous-duty
incinerators with stepped hearths and internal transfer rams use
a distinct burndown procedure. After the last charge in a given
campaign, each ram goes into a sequential burndown mode. The
internal ash rams, starting with the initial or drying hearth,
are operated in a mode that progressively increases the distance
of each stroke over a prescribed time period until all the waste
has been transferred to the next hearth. At this point, the
underfire air to the initial or drying hearth is shut off, and
the same sequence of operations is applied to the next hearth
until all waste material is discharged to the ash pit. This
burndown sequence is usually preset by the manufacturer but can
be changed if ash quality is poor.
Three alternatives to the fixed-hearth systems described
above are the rotary kiln, the Pulse-Hearth™ and the stoker. For
the rotary kiln the retention time of the waste for burndown is
determined by the rate of rotation and the angle of incline or
rake of the kiln. One manufacturer of continuous-duty MWl's uses
a Pulse-Hearth™ for moving waste material through the primary
chamber. The retention time of the waste for burndown in this
system is controlled by the frequency of the hearth pulses that
move the waste along the hearth. Another manufacturer provides a
stoker system to move waste through the primary chamber. The
stoker comprises a series of overlapping, alternating stationary
and movable grates. While a movable grate positioned over a
stationary grate is advancing, a movable grate positioned under
that stationary grate retracts to form a step 15 inches high.
This action causes waste to fall and mix as it moves across the
length of the stoker.
2.2.2.6 Control of Secondary Chamber Gas Residence Time.
In the modern MWI, the secondary combustion chamber serves as a
reaction vessel to complete conversion of the organic materials
released from the primary chamber. Although some of the
carbonaceous material in entrained particulate matter may
22
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combust, most of the chemical reactions in the secondary chamber
are gas-phase reactions that involve volatile organic materials
released from the waste and oxygen in the secondary combustion
air. The specific reaction chains by which the organic material
is converted to C02 and H20 are not fully understood and are
likely to be quite complex. However, they are generally assumed
to behave according to first order reaction kinetics. Under such
an assumption, the rate of conversion of organic material to CO2
and H20 is a function of the temperature/time envelope provided
by the secondary combustion chamber. If the residence time is
not sufficient, given the system's operating temperature,
complete combustion of the organics and conversion of CO to C02
will not be accomplished.
The residence time in the secondary chamber is a function of
the size of the chamber and the volumetric flow through the
chamber. In its simplest form, the average residence time can be
calculated as:
At.
S
Eq. 1
where:
At - secondary chamber residence time, sec;
S -3
V = secondary chamber volume, m ,• and
O = combustion gas flow rate at secondary chamber
s ^
conditions, irr/sec.
The primary mechanism used to control residence time is
appropriate sizing of the secondary chamber during the design
process. Information collected from manufacturers indicates that
systems are sized to have secondary chamber residence times of
0.25 to over 2 seconds under normal operating conditions. The
two approaches that have been used to increase residence time are
to increase the size of a single chamber or to construct two
smaller chambers in series. For this latter approach, the two
chambers are typically called the secondary and tertiary chamber.
respectively. In theory, the two approaches should provide
23
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equivalent residence times and emission reductions. No data that
demonstrate differences have been identified.
Volumetric flow also affects residence time. Typically,
this flow is not controlled directly in MWI's. Rather, it is a
function of the feed rate, combustion air, and temperature
control systems described earlier. Consequently, controlling
these parameters to levels that are within design specifications
is the key to achieving design secondary chamber residence times.
Secondary chamber residence times affect the control of
organic emissions, CO concentrations, and, to a lesser extent, PM
emission rates. Residence time does not affect metals or acid
gas emissions. Increases in residence time at a given
temperature decreases emissions of CO and organic pollutants, if
properly mixed, by giving the oxidation reactions more time to
move to completion. Increased residence time can also decrease
PM emissions by providing additional time for the fixed carbon in
entrained particles to combust and by allowing more complete
combustion of condensible hydrocarbons.
2.2.2.7 Control of Secondary Chamber Mixing. The reaction
rate for organic materials in the secondary chamber is a function
of the temperature/time envelope provided by the chamber, but the
reaction will proceed toward completion only if the gas phase
organics from the primary chamber are well-mixed with the oxygen
from the secondary chamber combustion air. Hence, complete
combustion of the organics and CO in the secondary chamber
requires turbulent mixing of the primary chamber exhaust and
secondary chamber combustion air. As described in the paragraphs
below, manufacturers have used a variety of techniques to promote
turbulent mixing in the secondary chamber.
Two general types of techniques are used by manufacturers to
promote secondary chamber mixing. First, all manufacturers use
the location, direction, and velocity of the secondary air ports
to promote turbulent flow, although specific designs vary among
the different manufacturers. In addition, some manufacturers use
constrictions or physical barriers such as baffles in the
secondary chamber to increase gas velocity and create turbulent
24
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flow. Note' that both types of techniques are related to the
design rather than the operation of the facility. However, the
system operation does play a key role in maintaining turbulent
conditions in that the different mechanisms designed to promote
mixing are related to combustion air and combustion gas
velocities. If the system operating rate drops to the point that
gas velocities drop below minimum design specifications,
insufficient mixing can result.
Each manufacturer has a unique system for introducing
combustion air to the secondary chamber. Most MWI's contain a
short, narrow passage between the primary and secondary chambers
that is known as the flame port. Many designs introduce most of
the secondary air into this flame -port at a direction
perpendicular to the flow of the primary chamber exhaust gases.
The high gas velocities in this area are purported to generate a
well mixed stream. While many systems introduce the major
portion of secondary combustion air into the flame port, other
designs introduce the air at different locations in the secondary
chamber. Common designs include high-velocity air jets at
multiple axial locations that introduce combustion air in a
direction perpendicular to the gas flows at velocities sufficient
to penetrate to the center of the chamber and airports near the
flame port opening that introduce air tangential to the gas
stream to promote cyclonic flow. One system introduces secondary
combustion air through a device known as a thermal exciter.13
Although these designs have different geometries, they are all
designed to achieve complete penetration of the primary chamber
exhaust gas cross-section by the combustion air and to promote
gas turbulence throughout the secondary chamber.
In addition to careful introduction of secondary air, some
manufacturers use physical restraints in the secondary chamber to
promote turbulence. One manufacturer uses a long, narrow,
cylindrical secondary chamber to increase gas velocities and
thereby promote turbulence. Other designs include locating
baffles at multiple positions along the chamber and using a
refractory choke ring about halfway along the cylindrical chamber
25
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to generate" turbulent flow. No quantitative measures of the
effect of these physical measures on gas turbulence are
available.
A well-mixed gas stream is needed to ensure intimate contact
of organics in the gas stream with oxygen. Mixing also provides
a more uniform temperature profile throughout the chamber and
minimizes potential "short-circuiting" by portions of the gas
stream. Good mixing reduces both organic and CO emissions and
may provide some reduction in PM emissions. However, no
quantitative measures of mixing are available.
2.2.2.8 Control of Solids Mixing in the Primary Chamber.
Solids mixing can have conflicting impacts on the control of
emissions from MWI's. On the one hand, good mixing of the solids
in the bed is needed to promote uniform temperatures in the bed,
enable release of all volatile organic materials, and provide
contact between all solid surfaces and the primary combustion air
to ensure complete fixed carbon burnout. In contrast, excessive
bed turbulence can lead to increased particle entrainment and,
consequently, increased PM and metals emissions. Consequently,
bed mixing or turbulence must balance these effects.
The two principal types of mechanisms that are used to
control solids mixing are the physical processes that are used to
move the waste along the primary chamber hearth and turbulence
generated by injection of primary combustion air into the bed.
Primary combustion air injection systems are discussed in
Section 2.2.2.9. The paragraphs below discuss the physical
mechanisms used to promote appropriate bed turbulence in three
types of units--the fixed-hearth system (both single and multiple
hearth) , the pulse-hearth system, and the rotary kiln system.
The basic concepts for these three systems are described in
Section 2.2.2.5; the discussion below focuses on system
parameters that affect solids mixing.
The most common MWI configuration is the fixed-hearth
system. Historically, these systems were constructed with a
single hearth and had either no ram (smaller, batch-fed units) or
a single feed/ash ram. Feed/ash ram systems are found on larger
26
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MWI's both to move waste/ash through the MWI effectively and to
provide solids mixing. Newer designs contain multiple (three to
four) hearths with a separate ram for each hearth. Single-hearth
systems may have only a feed ram where new waste charges provide
solids mixing. In general, these multiple-hearth systems mix
solids in the bed better than do the single-hearth systems. The
degree of turbulence in the bed of these systems can be
controlled by controlling ram speed and ram stroke length. An
increase in either of these parameters is likely to increase
turbulence in the bed.
One alternative to the fixed-hearth design is the pulse-
hearth design. Solids on these hearths are mixed via the pulsing
action used to move the solids along the hearth. The degree of
solids turbulence is a function of the pulse intensity. The
manufacturer of this system claims to achieve better solids
mixing than is achieved in fixed hearth units, but no data have
been received to support this claim.
In the past 3 years, a limited number of rotary kiln MWI's
have been installed in the United States. The rotary action
generates substantially greater solids mixing than is achieved in
either the fixed-hearth or the pulsed-hearth system. Within a
given kiln, the degree of turbulence in the waste bed is a
function of the rotational speed of the kiln, the angle of
incline or rake of the kiln, waste characteristics, and the waste
feed rate.
Ideally, control of solids mixing (or turbulence) in the
primary chamber should be optimized to address conflicting
objectives--maximizing ash burnout and minimizing particle
entrainment in the exhaust gas from the primary chamber. In
general, increasing mixing increases burnout, but it also
generates higher concentrations of particles in the exhaust gas.
2.2.2.9 Sizing and Location of Combustion Air Ports in the
Primary Chamber. The sizing and location of primary chamber
combustion air ports are designed to address three objectives
concurrently--to provide uniform airflows in the bed to control
volatiles release, to promote complete fixed-carbon burnout, and
27
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to minimize" particle entrainment in the primary chamber exhaust
gas. Also, systems are designed to maintain bed temperatures at
levels that limit clinker formation and refractory damage.
Generally, combustion air is introduced to the primary
chamber as "underfire" air, but some systems introduce the
majority of primary chamber air through ports located immediately
above the waste bed. While most systems do introduce underfire
air into the side or bottom of the waste bed, the designs vary
widely with respect to location of the injection ports, port size
and geometry, and distribution of airflows along the combustion
zone. Locations of the air ports include the side walls below
bed levels, openings in the hearth itself, and the centerline of
the ash ram. Geometries range from thin slots in the side walls
that run the length of a hearth to small-diameter, circular
openings in the hearth and the side walls to large-diameter low-
velocity openings in the side walls and ash rams. Manufacturers
also have different methods for distributing air along the
hearth. Some systems introduce air uniformly along the total
length of the hearth or along all hearths in a multiple hearth
system (with the possible exception of the first hearth). Other
systems vary the flow rates along the length of the hearth, with
some systems providing higher flows at the charging/drying hearth
and others providing higher flows at the discharge end.
Irrespective of the specific mechanism employed, the
underfire air system design has three key impacts on emissions.
First, the degree to which the system can operate in a consistent
fashion without plugging or malfunctioning, affects how well the
release of volatiles to the secondary chamber can be controlled.
Controlling the release of volatiles to the secondary chamber
affects CO and organic pollutant emissions. To reduce the
potential for air port plugging, some continuous MWI's are
designed with a mechanism that allows combustion air ports to be
rodded or cleaned out while the MWI is in operation.
Intermittent and batch MWI's require that the air ports be rodded
out on a daily basis prior to the start of the burn. Second, the
degree to which the system provides good oxygen contact with ash
28
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surfaces as' the ash moves toward the discharge end of the chamber
affects ash burnout. Finally, the turbulence generated by the
combustion air system affects particle entrainment and PM
emissions.
2.2.2.10 Steam In-iection in the Primary Chamber. Some
manufacturers use steam injection into the ash bed to facilitate
burnout of fixed carbon in the ash bed and at the same time help
prevent hot spots and clinker formation on the hearth.14'15 The
steam is injected into the ash bed through the underfire air
ports. The steam reacts with the fixed carbon in the waste/ash
bed to produce CO and hydrogen (H2)• This reaction is an
endothermic reaction (absorbs heat), thus reducing the
temperature in the ash bed. (The'normal oxidization reaction of
oxygen with carbon is exothermic and evolves heat, causing the
ash bed temperature to rise and potentially resulting in hot
spots adjacent to the air ports). The steam injection promotes
complete burnout of the ash, and also helps to prevent hot spots
in the ash bed adjacent to the air ports which might promote
slagging.
Different techniques are used by different manufacturers for
injecting steam. One manufacturer uses a series of staged
hearths in its large incineration designs. The steam is injected
through underfire ports in the last hearth in lieu of air.15
Another manufacturer of an intermittent-duty incinerator mixes
the steam with the underfire air, which is distributed throughout
the entire area of the hearth.14 During operation, steam
injection is not used during the first part of the incineration
cycle. Once an ash bed is developed, the steam injection is
activated, and the steam is injected with the combustion air; the
amount of air injected is reduced by the volume of steam
injected.
2.2.2.11 Operator Training. Previous sections identify key
operating parameters for the incineration systems and indicate
the relationship between these parameters and potential
emissions. No studies have been conducted to determine the
effect of operator training (or the lack thereof) on emission
29
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levels. Nonetheless, it is reasonable to presume that operator
training can result in the reduction of emissions. An operator
who understands how the key operating parameters affect emissions
and who knows the preferred operating procedures can operate and
maintain the incinerator and APCS in a manner that minimizes
emissions.
Using proper waste charging procedures for an incinerator is
an example of an operation that can affect emissions. Training
of the operator responsible for charging of the incinerator helps
to ensure that the incinerator is charged in such a manner as to
minimize emissions. The operator should be trained in the proper
handling procedures and steps for charging the unit to minimize
fugitive emissions during charging. These procedures typically
are provided by the manufacturer in the MWI operation manual.
Also, maintaining the proper frequency and size of each charge
insures that the proper charge rate (heat input rate) is
maintained, thereby enhancing controlled combustion. Many newer
incinerators use sophisticated controls that result in an
automated operation with few functions under the direct control
of the operator. For example, the system may include the
automatic control of the secondary burner and combustion air
rates as a result of temperature output from the secondary
chamber thermocouple. Also, some newer systems include an
automated feed system which controls the frequency and weight of
the charges. However, using automated controls does not
alleviate the need for operator training; it simply refocuses the
areas in which training is required. Although the operator may
not need to understand the theoretical aspects of how the
automated control system operates, someone responsible for the
operation of the unit must understand how the system is designed
and intended to operate, how to establish proper setpoints, and
how to recognize the telltale signs of a malfunction or need for
calibration/adjustment.
Operator training with respect to proper maintenance and
operation is important. If the incinerator and its combustion
control system are not properly maintained, then the system will
30
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not operate" properly. The result is likely to be increased
emissions. For example, if the primary chamber underfire air
ports are not maintained such that they remain clear of debris,
the combustion air distribution will be affected and will affect
the primary chamber temperature and, ultimately, emissions and
ash quality.
3.0 ADD-ON AIR POLLUTION CONTROL SYSTEMS
Many APCS's consist of one add-on control device to control
particulate matter (PM) and another to control acid gases
(primarily hydrogen chloride [HC1] gas). These add-on control
devices can be wet scrubbers, dry scrubbers, or fabric filters.
The following sections describe these add-on control devices.
Each section contains a general description of the control device
physical characteristics (i.e., the various pieces of equipment
and how they fit together), how the control device cleans the
flue gas of its primary pollutant(s) and its effectiveness, the
key operating parameters, and a qualitative discussion of how
much co-control of other pollutants can be achieved.
Additionally, each section contains a qualitative discussion of
the factors that affect the performance of the control device in
controlling PM, acid gases, metals, and CDD/CDF, including
specific design features and gas stream characteristics.
This section describes wet scrubbers, dry scrubbers, and
fabric filters and their application to MWI's. Section 3.1
describes venturi, packed-bed, and other types of wet scrubbers.
Section 3.2 describes pulse-jet fabric filters. Section 3.3
describes dry sorbent injection and spray dryer dry scrubbers.
3.1 WET SCRUBBERS
A venturi scrubber in combination with a packed-bed scrubber
is the most common wet scrubber system used to control emissions
from MWI's. Venturi scrubbers are used primarily for PM control
and packed-bed scrubbers are used primarily for acid-gas control.
However, both scrubber types achieve some degree of control of
both PM and acid gases. A large amount of information and
emission test data are available for these scrubber types. Other
types of wet scrubbers that have found limited application to
31
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control emissions from MWI's include the Rotary Atomizing™
scrubber, the Ionizing Wet Scrubber™, the Calvert collision
scrubber, and the steam-ejector scrubber.
Section 3.1.1 describes wet scrubbing mechanisms. Venturi
and packed-bed scrubbers are described in detail in Sections
3.1.2 and 3.1.3. The other scrubbers mentioned above with
potential application to MWI's are briefly described in
Section 3.1.4.
3.1.1 Wet Scrubbing Mechanisms
Wet scrubbers collect particles primarily through the
mechanisms of impaction and diffusion and remove gaseous
pollutants primarily through absorption. The following
subsections describe these mechanisms.
3.1.1.1 Collection of PM. Wet scrubbers capture relatively
small dust particles with relatively large liquid droplets.
These droplets are produced by injecting liquid at high pressure
through specially designed nozzles, by aspirating the particle-
laden gas stream through a liquid pool, or by submerging a
whirling rotor in a liquid pool. These droplets collect
particles through two primary collection mechanisms: impaction
and diffusion. With both of these mechanisms, PM collection
increases with an increase in relative velocity (liquid- or gas-
phase input) and a decrease in liquid droplet size.16
In a wet scrubbing system, dust particles with diameters
greater than 1.0 micrometer (/im) tend to follow the streamlines
of the exhaust stream. However, when liquid droplets are
introduced into the exhaust stream, particles cannot always
follow these streamlines as they diverge around the droplet
(Figure 4}. The particle's mass causes it to break away from the
streamlines and impact on the droplet. Impaction is the
predominant collection mechanism for scrubbers with a gas stream
velocity greater than 0.3 m/sec (1 ft/sec), which is well below
the gas stream velocity, experienced in most scrubbers.17'18
Very small particles (less than 0.1 /xm in diameter)
experience random movement in an exhaust stream. These particles
are so tiny that they are "bumped" by gas molecules as they move
32
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Gas streamlines
Particle
/ \ Droplet
Figure 4. Impaction
18
in the exhaust stream. This bumping, or bombardment, causes the
particles to move first one way and then another in a random
manner, i.e., to diffuse through the gas. This irregular motion
(or diffusion) can cause the particles to collide with a droplet
and be collected (Figure 5),19 The rate of diffusion depends on
relative velocity, particle diameter, and liquid droplet
diameter. Collection by diffusion increases as particle size
decreases. This mechanism enables certain scrubbers to remove
the very tiny particles (smaller than 0.1 Jim) effectively.19
In summary, impaction is the predominant PM collection
mechanism for particles greater than 1.0 /mi while diffusion is
the predominant mechanism for particles smaller than 0.1 jmi. For
particles between 0.1 and 1.0 /im, neither mechanism dominates;
particles in this size range are collected by both mechanisms.
However, particles in this size range are not collected as
efficiently as are either larger particles by impaction or
smaller particles collected by diffusion.18'19
3.1.1.2 Absorption of Gaseous Pollutants. The process of
dissolving gaseous pollutants in a liquid is referred to as
absorption. Absorption occurs when mass is transferred as a
result of a concentration difference between the liquid and the
gas from which the contaminant is being removed. Absorption
33
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Particle
Gas streamlines
\ Droplet
Figure 5. Diffusion.19
continues as long as a concentration differential or lack of
equilibrium exists. In absorption, equilibrium depends on the
solubility of the pollutant in the liquid.20
To remove a gaseous pollutant by absorption, the exhaust
stream must be brought into contact with a liquid. Figure 6
illustrates the three step process involved in absorption.
First, the gaseous pollutant diffuses from the bulk area of the
gas phase to the gas-liquid interface. Second, the gas molecule
moves (transfers) across the interface to the liquid phase. This
step occurs extremely rapidly once the gas molecules (pollutant)
arrive at the interface area. Third, the gas molecules diffuse
into the bulk area of the liquid, thus making room for additional
gas molecules to be absorbed.
The rate of absorption depends on the diffusion rates of the
pollutant in the gas phase (first step) and in the liquid phase
(third step). Gas diffusion and, therefore, absorption can be
enhanced by:
1. Providing a large interfacial contact area between the
gas and liquid phases;
2. Providing good mixing of the gas and liquid phases
(turbulence), and
34
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Gaseous
pollutant
Figure 6. Absorption
20
3. Allowing sufficient residence, or contact, time between
20
the phases for absorption to occur.
A very important factor affecting the amount of a pollutant
that can be absorbed is its solubility. The solubility of the
pollutant governs the amount of liquid required and the necessary
contact time. More soluble gases require less liquid. Also ^
more soluble gases will be absorbed faster. (For example HC1 ,s
absorbed more rapidly than S02 in water because HC1 x. much more
soluble.) Solubility is a function of both the temperature and,
to a lesser extent, the pressure of the system. As temperature
increases, the amount of gas that can be absorbed by a liquid
decreases. For this reason, some absorption systems use xnlet
quench sprays to cool the incoming exhaust stream, thereby
increasing absorption efficiency. Pressure affects the
solubility of a gas in the opposite manner. When the pressure of
a system is increased, the amount of gas absorbed generally
21
*
increases .
3.1.2
i grubbers
This section provides a general description of a venture
scrubber system including equipment components, the gas cleaning
process, and key operating parameters followed by a discussion of
the factors affecting the performance of the venturi.
35
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3.1.2.1 General Description. A venturi scrubber system
typically is made up of the following components:
1. Scrubber vessel;
2. Cyclonic separator;
3. Induced-draft (ID) fan;
4. Liquid recirculation system; and
5. System controllers.
These components are described in the following paragraphs.
Venturi scrubbers are designed to remove PM primarily by
impaction through high-energy contact between the scrubbing
liquid and the suspended PM in the gas stream.22 Figure 7
illustrates a simplified venturi scrubber vessel consisting of a
converging section, a throat section, and a diverging section.23
The high-energy contact is achieved by directing the scrubbing
liquid and the gas stream to the throat section. The gas stream
to be scrubbed enters the converging section (or quench) and as
the gas flows towards the throat and the cross-sectional area
decreases, the gas velocity and turbulence increase.23'24 The
exhaust gas, pulled through the throat by the system's ID fan and
forced to move at extremely high velocities in the throat, shears
the liquid from the throat walls and atomizes the liquid into a
large number of small droplets.23'24 (Another method of
producing droplets is to atomize the liquid by supplying high-
pressure liquid through spray nozzles with small orifices),24
Impaction of the PM on the droplets occurs in the venturi throat
and the exhaust stream exits through the diverging section where
it is forced to slow down.23
In venturi applications on MWI's, either a special quench
section and/or the converging section of the scrubber vessel acts
as a quench, both to saturate and to cool the gases prior to the
venturi throat. The hot MWI exhaust gas is cooled by evaporating
the quench liquid to an equilibrium temperature that, for most
incinerator applications, lies between 66° and 85°C
(150° and 185°F),25
Two types of venturi scrubbers may be installed in MWI
applications--wetted- and nonwetted-approach Venturis. Wetted-
36
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Converging
section
- Throat
^ Diverging
section
Figure 7. Simplified venturi scrubber configuration
37
23
-------
approach Venturis are the most common. The primary difference
between these two types is that in a wetted-approach venturi,
which is illustrated in Figure 8, the scrubbing liquid is
introduced through nozzles located at the top of the converging
section to wet the scrubber walls. In a nonwet ted-approach
venturi, the liquid is injected through nozzles that direct the
liquid directly into the throat without wetting the walls.
Wetted-approach Venturis are used when inlet gas streams are at
temperatures greater than 93°C [200°F]. Coating the scrubber
walls and throat with liquid reduces the tendency for PM to
abrade or cake on the walls or throat.26"28
Because of the variations in MWI gas flow rate caused by
waste charging and combustion air modulation, most venturi
installations, in addition to being wetted-approach Venturis, are
variable throat Venturis. Figure 9 illustrates a wetted-
approach, variable throat, venturi scrubber.29 Variable throat
Venturis use either a throat insert or an adjustable plate to
decrease or increase the cross-sectional area of the venturi
depending on the gas flow conditions.30 The purpose of the
variable throat is to maintain constant gas velocity across the
throat, thereby maintaining venturi PM collection performance.
Although a variable throat venturi can create restrictions in gas
flow that cause the MWI draft to become positive, a venturi
installed with a variable speed ID fan maintains negative draft
in the MWI. As shown in Figure 9, scrubbing liquid also can be
introduced through the throat insert.
The scrubbed gas from the venturi throat passes into the
diverging section where the gas slows down.23 Typically, the
base of the diverging section is submerged in a pool of liquid to
prevent abrasion of the metal surfaces by the collected PM.31'32
This configuration is called a wetted or flooded elbow and is
illustrated in Figures 9 and 10.
The PM entrained in the droplets from the venturi scrubber
subsequently is collected either in the packed-bed scrubber or in
a cyclonic separator. Typically, in MWI applications, the gas
passes from the wetted elbow to the base of a packed-bed scrubber
38
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Liquid
inlet
Figure 8. Schematic of wetted-approach venturi scrubber.
39
16
-------
VARIABLE VENTURI SCRUBBER
WITH WETTED ELBOW
HOT GAS
IWLET
•THIMBLE"INLET
scauwiNe LIQUOR
TO THROAT
(BOX OF LIQUID)
ALTERNATE OR SUPPLIMENTAL
NOZZLE LOCATION FOR VERY
HIGH TEMPERATURE GASES
TANGENTIAL LIQUID INLETS
(40X OF LIQUID)
CONVERGING INLET-WETTED
NITH TANGENTIAL LIQUID
SCRUBBING LIQUOR
TO THROAT
THROAT INSERT
THROAT-CROSS SECTION
VARIES NITH INSERT
POSITION
EXPANDER SECTION
WETTED ELBOW-FILLS
WITH LIQUID
HYDRAULIC OR MECHANICAL
ADJUSTMENT FOR THROAT
Figure 9. Schematic of wetted-approj
throat venturi scrubber."
:h, variable
40
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Cyclonic
separator
Flooded
elbow
Figure 10. Venturi scrubber illustrating the flooded (wetted)
elbow and exhaust gases passing to a cyclonic separator.-3-*
41
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used for acid gas control where the entrained PM mixed with the
scrubbing liquid is ultimately removed from the system with the
scrubber liquid discharge (blowdown). (Packed-bed scrubbers are
described in Section 3.1.3.) However, in those applications
where a packed-bed scrubber is not used, the gas passes from the
wetted elbow to the base of a cyclonic separator (see Figure 10).
The gas is introduced tangentially tp the cyclonic separator
where the particles and moisture are thrown outward to the walls
of the cylinder.33 The droplets coalesce and drop down the walls
to a central location carrying the PM with them.33
The ID fan of a venturi scrubber system is located after the
cyclonic separator (or packed-bed scrubber if so equipped) and
pulls the exhaust gas through the system. Some installations
utilize a variable-speed ID fan that can be tied to the control
of the venturi throat insert and/or the MWI primary chamber draft
so that the desired draft in the MWI primary chamber and a
constant venturi throat pressure drop can be maintained. Other
systems utilize a single speed ID fan equipped with a damper to
control airflow.
The scrubber liquid recirculation system comprises a caustic
solution tank, caustic addition equipment, recirculation pump,
and piping. The liquid is recirculated through the system
continuously. In many systems, a single recirculation pump is
used (even on systems with packed-bed scrubbers) with a backup
pump in parallel. A small blowdown stream is bled off to remove
collected PM and a fresh water makeup stream is added to the
system to replace the blowdown and any evaporative losses.
Because the venturi scrubber liquid also absorbs a portion of the
HC1 in the exhaust gas, the pH of the scrubber liquid decreases.
In most venturi scrubber applications, the scrubber liquid is a
caustic solution used to neutralize acid gases and to prevent
corrosion of equipment. A pH meter monitors changes in the
scrubber liquid pH and a controller adds caustic solution to the
system to maintain a pH of 7.0 or less.22
Venturi system controllers include those for the venturi
throat insert, caustic feed, makeup water, and emergency water
42
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quench for"high-temperature excursions. The venturi throat
insert is controlled either pneumatically or hydraulically to
maintain constant throat velocity. The throat insert is moved
upward or downward based on the pressure drop measured across the
venturi throat. The rate at which caustic is added to the system
is controlled in order to maintain a preset pH, typically 7.0 or
slightly less.22 The rate at which makeup water is introduced to
the scrubber typically is set at a rate necessary to replenish
the liquid lost to blowdown and evaporation.
3.1.2.2 Factors Affecting Performance. The performance of
the venturi scrubber relative to PM, acid gas, metals, and
CDD/CDF emissions is affected by the venturi design and operating
variables and also by key MWI operating variables. Key venturi
scrubber design and operating variables are the pressure drop
across the venturi throat, the liquid/gas (L/G) ratio, and the
scrubber liquid pH, surface tension, and turbidity (i.e., solids
content). Key process parameters that can affect venturi
scrubber performance are the particle size distribution and the
variations in temperature, flow rate, and pollutant
concentrations that result from the heterogeneous nature of the
MWI process.
Venturi scrubbers are used on MWI's primarily to control PM
emissions. The PM collection efficiency in a venturi scrubber
system increases as the pressure drop increases.34 Figure 11
shows this relationship based on the particle size distribution
in Figure 12. The static pressure drop is a measure of the total.
amount of energy used in the scrubber to accelerate the gas
stream and to atomize the liquid droplets. In MWI applications.
a common venturi scrubber pressure drop is 7.5 x 103 Pascals (Pa)
(30 inches of water column [in. w.c.]) but can range from
3.7 x 103 to 1.5 x 104 Pa (15 to 60 in. w.c.). The pressure drop
across the venturi is a function of the gas velocity and L/G
ratio and in practice is a surrogate measure for gas velocity.36
The Calvert equation can be used to predict the pressure
drop for a given throat velocity. The Calvert equation is:
43
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VERT AII5: DIFFERENTIAL PRESSURE (INCHES U.S.}
mil AIIS: Z COLLECTION EFFICIENCY
: FROM 0 TO 100 IN STEPS OF 1
Figure 11. Venturi scrubber collection efficiency
versus differential pressure.35
44
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.5
30.
100
VERT AIIS: AERODYNAKIC PARTICLE SIZE CB1CRONS)
«u tin.
SIIE
Figure 12. Typical medical waste incinerator exhaust
gas particle size distribution. D
45
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AP = (5 x 10~5) v2 (L/G)
where
£p = pressure drop, in. w.c.
v - gas velocity in the venturi throat, feet/second, and
L/G - liquid-to-gas ratio, gallons/1,000 actual cubic feet
(gal/Macf).
The equation implies that pressure drop is equal to the power
required to accelerate the liquid to the gas velocity. The
Calvert equation predicts pressure drop reasonably well for the
range of L/G ratios from 668 to 1,604 liters/1,000 actual cubic
meter (L/Macm) (5 to 12 gal/Macf). At L/G ratios above
1,604 L/Macm (12 gal/Macf), measured pressure drops are normally
about 80 percent of the value predicted by the Calvert equation.
In practice it has been found that at L/G ratios less than
401 L/Macm (3 gal/Macf), there is an inadequate liquid supply
available to completely cover the venturi throat. Most venturi
scrubbers are designed for liquid feed rates between 936 and
1,337 L/Macm (7 and 10 gal/Macf), and there is virtually no
change in performance over this range given that the pressure
drop across the venturi throat remains constant.37
The performance of a venturi scrubber in removing PM is
strongly affected by the size distribution of the PM. For
particles greater than 1 to 2 /zm in diameter, impact ion is so
effective that penetration of particles in this size range
through the venturi is quite low. However, penetration of
smaller particles, such as the particles in the 0.1 to 0.5 pirn
range, can be high. Small particle size distribution, resulting
from the condensation of partially combusted organic compounds
and metallic vapors, is typical for combustion sources including
MWI's.38
To attain a high PM collection efficiency, venturi scrubbers
need to achieve high gas velocities in the throat. At normal
venturi pressure drops be.tween 5 x 103 and 1.5 x 104 Pa (20 and
60 in. w.c.), the gas velocity in the throat section typically
lies between 30 and 120 meter/second (100 and 400 feet/second).34
These high gas velocities atomize the water droplets and create
46
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the relative velocity differential between the gas and the
droplets to effect particle-droplet collision.
The high exhaust gas velocities in the venturi result in a
very short contact time between the liquid and gas phases,
thereby limiting gas absorption into the scrubber liquid.34 The
limited residence time limits the amount of vaporous metallic and
organic compounds that may be absorbed. However, because of the
high solubility of HC1 in water, a significant quantity of HC1
may be absorbed even though the residence time is short. One
vendor claimed an HC1 removal efficiency of 90 percent across a
Venturi scrubber.39
Other variables related to venturi scrubber performance are
the liquid surface tension and liquid turbidity. If surface
tension is too high, some small particles that impact on the
water droplet will "bounce" off and not be captured. High
surface tension also has an adverse effect on droplet formation.
However, surface tension typically does not significantly impact
scrubber performance. High liquid turbidity, i.e., high
suspended solids content, will cause erosion and abrasion of the
venturi section and ultimately lead to reduced performance -of the
system.40 Therefore, the presence of a blowdown stream to remove
suspended solids is important.
When hot MWI exhaust gases are quenched and saturated in the
converging section of the venturi, an equilibrium temperature of
between 66°.and 85°C (150° and 185°F) typically is achieved.41
In this temperature range, volatile metals and unburned organics
condense.41 As vaporous metals and organic constituents such as
A O
CDD/CDF cool, they condense, or agglomerate, on PM. The
greater the cooling, the greater these condensation and
agglomeration effects.42
The variations inherent in the operation of MWI's translate
to variations in gas stream characteristics including
temperature, flow rate, and pollutant concentrations. In many
MWI applications, a waste heat recovery boiler (WHB) is used both
to recover heat for use at the facility and to cool the MWI
exhaust gases prior to an APCS. The WHB tends to damp the
47
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the
to
variations in the exhaust gas temperature with the result that
the WHB outlet temperature fluctuates far less than the exhaust
gas temperature. With a L/G ratio of up to 1,337 L/Macm
(10 gal/Macf) , this small fluctuation does not affect the
performance of the venturi significantly.
On venturi scrubbers controlling MWI's without a WHB,
MWI exhaust gas temperature variation can range from 927°
1260°C (1700° to 2300°F). Venturi scrubbers in these
applications may be equipped with special quench sections ahead
of the converging section to cool the gas stream. Emergency
quench nozzles may be.installed at the top of the converging
section that rapidly provide the. necessary quench water to cool
the gases and to prevent damage to the system in upset
conditions. If the gases are not cooled to the typical
equilibrium temperature between 66° and 85°C (150° and 185°F) ,
then the venturi will be less effective in condensing volatile
metals and organics.
Variations in MWI exhaust gas flow rate are compensated for
by a variable throat venturi. Variations in the MWI exhaust gas
flow rate arise during waste charging and during combustion air
modulation in the MWI. Venturi scrubbers perform optimally when
they operate at conditions that approach steady state. The
variable throat venturi adjusts the throat cross-sectional area
to maintain constant velocity across the throat.
Variations in pollutant concentration in the MWI exhaust gas
are dependent primarily on waste composition. For example,
changes in the chlorine content of the waste directly affect the
HC1 concentration in the exhaust gas. The PM and volatile
organics concentrations can also change as the combustion process
changes. Because venturi scrubbers are designed to remove a
certain percentage of the incoming PM based on the particle size
distribution and inlet loading, any increase in the inlet loading
is likely to cause an increase in the outlet PM loading because a
similar percentage of PM would be removed. Therefore, the
venturi scrubber system design must be based on the maximum gas
flow rate, PM loading, and pressure drop considering the particle
48
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size distribution. Similar effects would be likely on gaseous
pollutants, i.e., increases in HC1, metals, and CDD/CDF inlet
concentrations would cause increases in outlet concentrations of
these pollutants.
313 Parked-B^ figrubbers
' '
2
3
4
5
This section provides a general description of a packed-bed
scrubber system including equipment components, gas cleaning
process, and key operating parameters followed by a discussion of
the factors affecting the performance of the packed-bed.
3.1.3.1 "-™~i T^crintion. A packed -bed scrubber system
typically comprises the following components:
1. Scrubber vessel;
Packing media;
Mist eliminator;
ID fan;
Liquid recirculation system; and
6 System controllers.
These components are described in the following paragraphs along
with the packed-bed gas cleaning process.
Packed-bed scrubbers are designed to remove acid gases
(primarily HC1 and sulfur dioxide [SO21 ) by absorption of the
gases into the scrubbing liquid and subsequent neutralization.
An alkaline solution typically is used to maintain a constant
scrubber liquid PH to prevent corrosion of scrubber components.
The scrubbing liquid typically used is caustic solution (NaOH)
although sodium carbonate (Na2C03) and calcium hydroxide
(Ca[OH]2) (slaked lime) also can be used. When the acid gases
are absorbed into the scrubbing solution, they react with
alkaline compounds to produce neutral chemical salts. The rate
of absorption of the acid gases is dependent on the solubility of
the acid gases in the scrubber liquid; HC1 is absorbed rapidly
while SO, is absorbed more slowly. The neutralization reactions
are essentially stc-ichiometric, i.e., the stoichiometric ratio of
alkaline compounds added to the system to that required for
complete neutralization of the acid absorbed into the scrubber
solution is essentially 1:1 in packed-bed scrubbers.
49
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Packed-bed scrubber vessels used to control acid gases from
MWI's typically are countercurrent, vertical columns where the
gas flows upward through the scrubber vessel and the scrubbing
liquid flows downward. Figure 13 illustrates a countercurrent,
packed-bed absorber with packing media, liquid sprays, and a mist
eliminator.
Scrubbing liquid is evenly distributed by the liquid sprays
over the packing media and trickles down through the bed wetting
the surface of the packing and, thereby, exposing the gas to a
large, wetted surface area. The depth of the bed depends on many
factors including the type of packing used, pollutant concentra-
tion and solubility, the desired removal efficiency of
pollutants, type of scrubber liquid used, liquid and gas flow
rates, and system temperature. However, a packing depth of 1.5m
(5 ft) using Intalox® saddles has been reported.35 Other vendors
specify packing heights that range from 0.9m (3 ft) to 3m (10 ft)
without specifying packing type.44'45 The exhaust gas is forced
to make many changes in direction as it winds through the
openings of the packing media, thereby causing the gas to mix
with the liquid. The large surface area of liquid/gas interface,
the packing depth, and the random packing provide the necessary
contact area between liquid and gas, sufficient residence time,
and good mixing, respectively, for effective absorption to occur.
After passing through the packing, the gases flow through a
mist eliminator that removes entrained droplets of liquid that
may contain alkaline salts, absorbed acid gases, and PM. In a
combination venturi/packed-bed scrubber system, the venturi may
remove 90 percent of the PM from the MWI exhaust gas, and the
remaining particles can become entrained in droplets from the
packing media in the form of alkaline salts and other ultrafine
PM. Therefore, the appropriate mist eliminator must be selected
for the packed-bed scrubber to minimize PM emissions from the
overall combination system. Mesh-, chevron-, and diffusion-type
mist eliminators are available. At least one vendor has stated
that a venturi/packed-bed scrubber system equipped with mesh- and
chevron-type mist eliminators can achieve outlet PM
50
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Mist eliminator
Liquid sprays
Packing
Figure
13. Schematic of countercurrent packed-bed scrubber
51
43
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concentrations of 0.03 grains/dry standard cubic foot (gr/dscf)
while the diffusion-type mist eliminator can achieve
concentrations less than 0.01 gr/dscf.35'46
The ID fan, liquid recirculation system, and system
controllers were discussed above in Section 3.1.2.1 on venturi
scrubbers. With the exception of the variable throat and
emergency water quench controllers, these discussions also apply
to packed-bed'scrubbers.
3-1-3.2 Factors Affecting Performance. The performance of
the packed-bed scrubber relative to PM, acid gases, metals, and
CDD/CDF emissions is affected by the packed-bed scrubber design
and operating variables and also by key MWI operating variables.
Key packed-bed scrubber design and operating variables are
scrubbing medium, L/G ratio, packing height (liquid-to-gas
contact time), suspended solids content, pH, and type of mist
eliminator. Key MWI process parameters that can affect packed-
bed scrubber performance are variations in exhaust gas stream
temperature, flow rate, and pollutant concentrations that result
from the heterogeneous nature of the MWI process.
The scrubbing medium or liquid used in packed-bed scrubbers
to remove acid gases from MWI's typically is a caustic solution.
This alkaline solution absorbs acid gases from the MWI exhaust
gas stream and protects the scrubber components from corrosion by
neutralizing the acid gases. The high solubility of HC1 gas in
this solution enhances the absorption of the HC1 into the
solution and thereby enhances the effectiveness of the packed-bed
scrubber in removing HC1. When insoluble alkalis such as slaked
lime are used as a scrubbing medium in packed-bed scrubbers, the
suspended solids in the slurry deposit on the packing and cause
plugging.22 Therefore, caustic solution absorbs and neutralizes
acid gases, prevents corrosion, and elifenates plugging problems
associated with insoluble alkalis.
The L/G ratio of a packed-bed scrubber is a design variable
that is specified along with the packing height and packing media
to achieve a specific control efficiency for a gaseous pollutant.
A L/G ratio between 2,674 and 3,342 L/Macm (20 and 25 gal/Macf)
52
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•jc 4.4 45
is typical for packed-bed scrubber applications on MWI's."'**'
The countercurrent packed-bed scrubber (typically used in MWI
applications) does not operate effectively-if .there are large
variations in the liquid or gas flow rates.47 Generally, removal
efficiency is increased by an increase in the liquid flow rate to
the scrubber.48 However, if either the .liquid flow rate or gas
47
flow rate is too high, a condition called flooding may occur.
Flooding is a condition where the liquid is "held" in the
pockets, or void spaces, between the packing media and does not
drain down through the packing.47 The gas velocity at which
flooding occurs is called the flooding velocity.49 Flooding can
be reduced by reducing the liquid flow rate.48 In packed-bed
applications to MWI's, a pump provides a constant liquid flow
rate. The packed-bed diameter is sized so that the maximum gas
velocity to be experienced by the packed-bed lies between 50 and
75 percent of the flooding velocity.49
The performance of a packed-bed scrubber in removing acid
gases from the gas stream depends on the effectiveness of the
absorption process that takes place on the packing media. The
packing media provides a large surface area for liquid-to-gas
contact and promotes good mixing of the gas and liquid. The
height of the packing determines the liquid-to-gas contact time;
the greater the height, the greater the residence time. Packing
heights of 1.5M (5 ft) using 7.6 cm (3 inch) Intalox® saddles
have been reported.35 Manufacturers guarantee HC1 removal
efficiencies from 99 to 99.9 percent and S02 removal efficiencies
from 90 to 99 percent when a packed-bed scrubber is used in
conjunction with a venturi scrubber.35'44'45 The effectiveness
of the packed-bed scrubber in removing vaporous metals and
condensible organics such as CDD/CDF from the gas stream is
further enhanced as the gas stream is intimately contacted by the
liquid film on the packing because vaporous metals and
condensible organics may condense and be removed as PM.
The suspended and dissolved solids content and pH of the
scrubber liquid are monitored to maintain scrubber performance.
Solids accumulation at the entry to the packed bed and within the
53
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22
bed is a problem that interferes with the absorption process by
restricting liquid flow through the bed. To prevent solids
accumulation, an adequate scrubber liquid blowdown rate must be
maintained. Most manufacturers have designed their systems with
a set blowdown rate that removes suspended and dissolved solids
and that does not require shutdowns for solids removal.35'44'45
The pH typically is maintained at or slightly below 7.0 by
monitoring pH and adding caustic solution as appropriate.'
Maintaining this pH level is important to prevent corrosion
damage to scrubber components.
Selection of the appropriate mist eliminator is important to
achieve low PM emissions. As described in Section 3.1.3.1, the
mist eliminator removes entrained droplets of liquid that may
contain alkaline salts, absorbed acid gases, and PM. A
diffusion-type mist eliminator can achieve a three-fold reduction
in PM emissions over the traditional chevron- and mesh-type mist
eliminators.35'46
The variations inherent in the operation of MWI's translate
into variations in gas stream characteristics including
temperature, flow rate, and pollutant concentrations. A packed-
bed scrubber controlling emissions from an MWI typically is
located after a PM control device such as a venturi scrubber or a
fabric filter. In both of these cases, the MWI exhaust gas
temperature is reduced before it reaches the packed-bed scrubber.
In the case of the venturi scrubber, the MWI exhaust gases are
cooled and saturated in the venturi and enter the packed-bed
scrubber at a temperature between 60° and 85°C (140° and 185°F).
In the case of the fabric filter, the MWI exhaust gases may be
cooled initially by passing through a heat exchanger or WHB
before passing through the fabric filter and a quench prior to
the packed-bed scrubber. In either case, the temperature
variations that occur in the exhaust gases leaving the MWI are
damped and the gas stream temperature entering the packed-bed
scrubber will be within a relatively narrow range. Gas stream
temperatures in excess of 104°C (220°F) can damage or melt the
54
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plastic packing media that typically is used in these
scrubbers.50
Variations in MWI exhaust gas flow rate are compensated for
by the proper design and sizing of the packed-bed scrubber. As
already described, the liquid flow rate to the packed-bed
scrubber is set at a constant rate and the packed-bed scrubber
diameter is sized such that the maximum gas velocity experienced
by the system is 50 to 75 percent of the flooding velocity.
Therefore, as the gas flow rate varies in the MWI system,
sufficient liquid is available for effective absorption without
encountering flooding.
Variations in pollutant concentration in the MWI exhaust
depend primarily on waste composition. Because HC1 in the
exhaust gas is highly soluble in the scrubbing solution,
variations in HC1 concentration are not expected to affect the
performance of the packed-bed in removing HC1 if the packed-bed
has been properly designed for the maximum HC1 concentration to
be encountered. The effectiveness of the packed-bed scrubber in
removing CDD/CDF and metals will depend in large part on the
effectiveness of the system in condensing and subsequently
collecting the resulting fine PM. The collection efficiency of a
packed-bed scrubber in removing condensed metals and CDD/CDF is
unknown.
3.1.4 other Wet---Scrubbing Systems
Although venturi and packed-bed scrubbers are the systems
that historically have been installed most frequently for MWI
emissions control, other novel wet-scrubbing systems are
beginning to penetrate the MWI market. Four types of systems
that have been applied to various waste combustion processes are
the Rotary Atomizing™ scrubber, the Ionizing Wet Scrubber™
(IWS~), the Calvert collision scrubber, and the Hydro-Sonic®
scrubber. These systems have been used more frequently at
municipal or hazardous waste incineration facilities, but they
are being actively marketed to MWI facilities. Because the
number of MWI installations of these systems is quite limited,
very little information has been collected to date on the
55
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performance' of the systems or on the factors that affect
performance. Consequently, the discussion below is limited to a
brief description of each of the systems.
3.1.4.1 Rotary Atomizing™ Scrubbers.51"53 Rotary
Atomizing™ scrubbers are designed to remove PM primarily through
impaction and acid gases primarily through absorption. Figure 14
illustrates a schematic of a rotary atomizing scrubber showing
the major components listed above. The Rotary Atomizing™
scrubber comprises a quench vessel (on systems without a WHB), a
prespray tower, a rotary atomizer, mist eliminators, and a liquid
recirculation system. Because the liquid recirculation system is
an integral part of the quench vessel, prespray tower, and rotary
atomizer section of this scrubber and because it contains
separate recirculation loops for each of these components, it is
described first.
The liquid recirculation system on the rotary atomizer
scrubber is unique in that there are three scrubber liquid
recirculation loops. The liquid is staged in a countercurrent
direction with respect to the gas flow. There are three separate
scrubber liquid feed tanks that serve the rotary atomizer, the
prespray tower, and the quench vessel. The fresh, clean scrubber
liquid is fed to the rotary atomizer tank. Overflow from this
tank flows to the prespray tower tank and a purge from the
prespray tank then flows to the quench vessel. Slowdown from the
quench vessel then flows to a sewer discharge.
On systems without a WHB, the combustion gases from the MWI
are directed to the top of the quench vessel. The quench vessel
serves two functions: (1) to cool the MWI exhaust gases and
(2) to absorb a portion of the acid gases. The quench vessel
evaporatively cools the MWI exhaust gases (982° to 1204°C [1800°
to 2200°F]} to saturation (68° to 77°C [155° to 170°F] through
the introduction of the purge from the prespray section through
spray nozzles located at the top of the vessel. The alkaline
(NaOH) quench water converts a large portion of the HC1 and S02
gases into sodium chloride and sodium sulfate salts. Once the
total dissolved solids content has reached 15 percent in the
56
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57
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quench tank" feeding the quench vessel, a blowdown stream is
activated that removes the dissolved and suspended solids from
the system.
The saturated gases from the quench vessel (or from the WHB
if so equipped) then enter the prespray tower where mid-size PM is
removed by impaction on droplets produced by nozzles located at
four different levels in the tower. Acid gases are further
neutralized in the prespray tower. This tower operates at an L/G
ratio of 8,020 L/Macm (60 gal/Macf) to completely saturate the
gases prior to entering the rotary atomizer section. The tower is
served by a prespray tank that uses the overflow from the rotary
atomizer section as feed liquid. Liquid that exits the base of •
the tower unevaporated flows back into the tank and is recycled to
the tower.
The saturated gases from the prespray tower subsequently pass
to the rotary atomizer section of the system. Figure 15
illustrates the rotary atomizer. The rotary atomizer creates a
constantly renewed high velocity water curtain equivalent to a
2.6 x 105 mmHg (5,000 pounds per square inch [psi]) spray nozzle.
This water curtain is generated by means of a high speed rotating
disc, that atomizes the water droplets and propels them toward the
wall of the rotary atomizer housing. The droplets rebound off the
wall creating a dense water curtain that acts as a filter pad.
This dense spray of droplets removes PM through impaction, while
gases are collected by absorption. The pressure drop across the
rotary atomizing scrubber is about 7.5 mmHg (4 in. H20).
Scrubbing solution also is recirculated through the rotary
atomizer tank based on level control reward while fresh caustic
reagent is added based on pH control demand.
The gas then passes from the rotary atomizer section through
two Chevron-type mist eliminators that are used to collect and to
separate the water droplets from the gas stream. The liquid
collected by the mist eliminators is returned to the rotary-
atomizing section tank. The scrubber manufacturer claims that
this 2-stage mist elimination system is rated at 99+ percent
overall in removing droplets that are 2 microns or larger in size.
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HIGH-SPEED
INDUSTRIAL
GEARBOX
SCRUBBED OUTLET
GAS FLOW
SCRUBBING LIQUID
FEED PIPE
HIGHLY AUTOMIZED
LIQUID DROPLETS
PARTICULATE-LADEN
INLET GAS FLOW
Figure 15. Schematic of rotary atomizer module.52
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3.1.4.2 Ionizing Wet Scrubber™.54'55 The IWS™ uses a
combination of electrostatic forces and the common wet-scrubbing
phenomena to provide both PM and acid-gas control. The typical
system consists of a quench chamber to reduce gas temperature and
one or more of the modular "units" shown in Figure 16 in series.
Because each unit (or stage) acts to remove a nearly constant
fraction of the acid gas and PM, the control efficiency is
increased by staging these units.
Each unit in the system has two major sections. The gas
stream passes through the entry plenum into the ionizing section
of the unit. Here particles are charged as they pass between
wires powered by a high-voltage DC power source and small
grounded electrode "mini plates." The gas stream thus passes
into the charged particle scrubber, which is a horizontal,
cross-flow, packed-bed scrubber with a Tellerette® packing
material. Acid gases are removed from the gas stream by
absorption and particles are collected in the scrubber section by
a combination of impaction and image force attraction, an
electrostatic property that causes the charged particles to
migrate to the neutral packing surfaces. Particles with
diameters of 3 to 5 pirn and larger are collected on packing
surfaces by impaction. Smaller particles are collected by image
force attraction. Particles are removed from these surfaces by a
constant cross-flow of scrubbing liquor.
3.1.4.3 Calvert Collision Scrubber.56 The Calvert
collision scrubber is designed to achieve high collection of both
PM and acid gases. The system comprises four major components in
series: the quencher, the condenser/absorber, a collision
scrubber, and an entrainment separator. A modified system
without the condenser/absorber is available if only moderate
control efficiencies are required. The major components of the
system are described in the paragraphs below.
The hot gas from the MWI enters the dual flow quench
chamber. The unit is called dual flow because two separate
liquid streams are introduced to the gas stream at different
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pJ.;reCna'S.iESe:M-.-Snor: m-enseiy cnargec High voltage DC
DOAS- -o,; energy consumption
.c,-5. £.e~s-,ts-Coni.ni!Ci:s f'usnmc, orevents soncs Dune UD
facto'. AsseT.Diec Moames-Fast inexpensive fteio msiallation
AI- or::c'es cr.a-ge: as tney enter scruDDer section
P'as:,: Sne! anc internals-Corrosion Resistant Minimum maintenance
mlet-To 50.000 ACFM
Collection Surtaces-ConnnuouS'v fiusnec .'
scruDDer section
All scruDDer surfaces loacKing -Aater O'ME s"5
eiectncaiiy neutral Act as impingement sj"a:es
or coiieci particles tnrougn image force ai:rac:.o"
Tellerene packing is excellent impingement ta-;e:
ana nigniy efficient collector Also creates
water orootets tor additional imDinge^ei: anc
collection surfaces
Exhaust of IWS ca- oe
connecteo sirectiy :c sac-
fan or to anotne- IWS -o-
increases collection
efficiency
Seaieo High voltage DC Power Supply
No movm; Parts (oniy pump)
! : Recycled Liauio—For gas aosorotion soncs
flushing
Figure 16. Schematic of an ionizing wet scrubber™.
54
61
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points. First, fresh makeup water is added to the inlet to
provide a wetted approach. Just beyond the inlet, recycled
scrubber water is added to the gas stream. These two liquid
streams reduce the gas stream temperature to saturation levels,
about 66° to 85°C (150° to 185°F), depending on inlet temperature
and moisture content.
The saturated gas stream moves from the quencher into a
horizontal, cross-flow or a vertical, counterflow packed-bed
absorber. Generally, a caustic or lime scrubbing solution is
used in the absorber. The HC1 is removed from the gas stream and
additional gas cooling reduces the temperature to 49° to 54°C
(120° to 130°F). This temperature reduction results in
condensation of moisture from the saturated stream. Small
particles in the gas stream act as condensation nuclei. The
moisture condensation on the surfaces of the particles
effectively increases their aerodynamic diameter, thereby
enhancing their collection downstream in the entrainment
separator.
The gas stream moves from the condenser/absorber into the
collision scrubber. There the gas stream is split into two equal
streams, turned, and impacted head on. At the point of collision
of the two streams, particles are collected on larger droplets
via the impaction and interception phenomena described in
Section 3.1.1. The particle-laden droplets in the gas stream
then enter a multistage entrainment separator. There, the
droplets are removed from the gas stream by impaction.
Additional removal of HC1 also is achieved in the collision
scrubber and entrainment separator.
3.1.4.4 Hvdro-Sonic® Scrubber.57*58 Hydro-Sonic® scrubbers
comprise a family of wet scrubbers that have been used to control
PM and HC1 emissions on several waste incineration processes.
The design most likely to be used on MWI systems is the fan
drive, tandem nozzle shown in Figure 17. This design consists of
two subsonic nozzles equipped with water sprays in series. As
the water spray is injected into the high-velocity gas stream,
very fine high-velocity water droplets are generated. Collisions
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63
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between the" droplets and particles take place in the highly
turbulent flow regimes in the mixing tubes, as does absorption of
HC1 into the droplets. Cyclonic mist eliminators are then used
to remove the pollutant-laden droplets from the gas stream.
3.2 FABRIC FILTERS
Historically, fabric filters (or baghouses) have been used
to control PM and nonvaporous metals emissions from combustion
sources and'other industrial processes. Fabric filters are often
combined with other air pollution control techniques to achieve
control of acid gas and organic pollutant emissions in addition
to PM control. The two most common combinations are a fabric
filter downstream from a sorbent-injection system (typically dry
sorbent injection is used, but facilities can use spray dryers)
and a fabric filter and packed-bed scrubber in series. Other
components of these combined systems are discussed later in this
report and will not be addressed in this section. The discussion
below focuses on the fabric filter component of the systems with
reference to later discussions.as appropriate.
Fabric filters are typically classified with respect to
their location relative to the fan and to their type of cleaning
mechanism. All systems installed to date at MWI facilities have
been negative-pressure systems (i.e., systems installed upstream
from an induced-draft fan). Also, all of the systems use pulse-
jet cleaning, although some vendors indicate that they would use
a reverse-air system if a client so preferred.59'61 Because
pulse-jet systems dominate the industry, the discussion below
focuses on these systems.
The remaining discussion is divided into three subsections.
The first presents-a brief overview of fabric filter PM
collection principles. The second subsection presents a general
description of the pulse-jet fabric filter. It describes
components of the system and identifies key design and operating
variables. The final subsection identifies primary control
system and combustor design and operating variables that affect
performance and discusses how these factors affect the
performance relative to PM, HC1, metals, and CDD/CDF emissions.
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3.2.1 Fabric F.i 1 ter Co31 *»fit ion Principles
Fabric filtration systems have been used for years to
control PM emissions from a wide variety of industrial processes,
to collect product materials from manufacturing processes, and to
maintain dust loadings at acceptable levels in clean room
environments. A substantial amount of research has been
conducted on 'the performance of-these PM and dust control
systems. The results of this research have led to an
understanding of the overall performance of fabric filter systems
in removing particles from gas streams and of the specific
collection mechanisms that apply. For MWI exhaust streams
controlled by fabric filters in combination with dry sorbent
injection, information collected to date suggests that the fabric
filter also plays a role in controlling other pollutants.
However, the mechanisms of control for other pollutants are not
fully understood. This subsection describes those mechanisms
that are generally accepted as the key mechanisms for fabric
filtration of PM. It also briefly discusses the mechanisms that
are postulated to affect the control of other pollutants.
A fabric filter is a collection of bags constructed of a
fabric material (nylon, wool, or other) hung inside a housing.
The combustion gases are drawn into the housing, pass through the
bags, and exhaust from the housing through a stack to the
atmosphere. When the exhaust from the incinerator is drawn
through the fabric, particles are retained on the fabric
material, while the cleaned gas passes through the material. The
collected particles are then removed from the filter during the
pulse-jet cleaning cycle. The dusty material cleaned from the
bags falls to a collection hopper and is removed from the hopper
for transfer to a storage area or disposal site.
With a new filter, .the open areas in the fabric are of
sufficient size that particles easily penetrate the bag. Over a
short time, a cake builds on the bag surface; this cake acts as
the primary particle collection medium. Particles are collected
on a filter and cake by a combination of several mechanisms. The
most important are impaction, direct interception, and diffusion.
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As the" exhaust gas flows through the cake and filter, it
makes numerous turns around obstructions encountered in the cake
or filter media and creates a flow pattern characterized by
curved streamlines. In collection by impaction, the particles in
the gas stream have too much inertia to follow the gas stream-
lines around the fiber or through pores in the cake. They leave
the gas stream and deposit directly onto the fiber or the surface
of the cake. In the case of direct interception, the particles
have less inertia and barely follow the gas streamlines around
the fiber. If the distance between the center of the particle
and the outside of the fiber or pore is less than the particle
radius, the particle surface will contact the surface of the
fiber and be "intercepted." Impaction and direct interception
mechanisms account for 99 percent of the collection of particles
with an aerodynamic diameter greater than 1 pm. in fabric filter
systems.62'63
For submicron particles, such as those generated by
homogeneous condensation of volatile metals, diffusion acts as a
key collection mechanism. Small particles that are affected by
collisions on a molecular level behave individually through
random motions. The particles do not necessarily follow the gas
streamlines, but instead move randomly throughout the fluid, a
phenomenon called Brownian motion. At some point in their random
flow through the fluid, a fraction of these small particles come
in contact with a surface of the filter medium and are
collected.62'63
3.2.2 Pulse-Jet Fabric Filter Description62'63
A schematic of a pulse-jet fabric filter is shown in
Figure 18. The primary components of the systems are the bags
and auxiliary equipment, the housing that contains the bags, the
inlet or dirty-side plenum that receives combustion gases and
distributes them to the bags, the clean-air plenum that receives
the cleaned combustion gas from the bags before it is discharged
to the atmosphere, and the hopper and discharge system.
The bag compartment is separated from the clean-air plenum
by a flat metal plate called a tube sheet. In larger systems,
66
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Clean Air Plenum.
Blow Pipe.
Bag Retainer.
'/ °/ °/
Dirty Air Inlet and Diffuser'. •
To Clean Air Outlet
and Exhauster
Housing
-Tubular Filter Bags
•Dirty Air Plenum
Rotary Vatve Air Lock
Figure 18. Schematic of a pulse-jet baghouse
63
67
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the bag compartment is frequently separated into multiple,
smaller compartments. These compartments can be taken off-line
individually for bag cleaning or maintenance. However, most
smaller units, such as those used at MWI facilities, have a
single compartment with bags arranged in a rectangular array.
Within this compartment, bags are suspended from the tube sheet
and supported internally by rings or cages. Bags are held firmly
in place at the tube sheet by clasps and have an enclosed bottom
(usually a metal cap). Dust-laden gas is filtered through the
bag, depositing dust on the outside surface of the bag. All
pulse-jet systems filter the gas from the outside to the inside
of the bag.62'63
The dust cake is removed from the bag by a blast of
compressed air injected into the top of the bag tube. The blast
of high-pressure air stops the normal flow of air through the
filter. The air blast develops into a standing, or shock, wave
that causes the bag to flex as the shock wave travels down the
bag tube. As the bag flexes, the cake fractures, and deposited
particles are discharged from the bag. The shock wave travels
down and back up the tube in approximately 0.5 seconds.62
The blast of compressed air must be strong enough for the
shock wave to travel the length of the bag and shatter or crack
the dust cake. Pulse-jet units use air supplies from a common
header that feeds into a nozzle located above each bag. In most
baghouse designs, a venturi sealed at the top of each bag is used
to create a large enough pulse to travel down and up the bag.
Alternatively, some baghouses operate with only the compressed
air manifold above each bag. For either type system, the pres-
sures involved are commonly between 414 and 689 kPa (60
and 100 psig).
As the shock wave moves down the bag, dust is released from
the bag surface into the open area on the dirty side of the bag.
A portion of the dust is immediately entrained in the incoming
gas stream and deposited on the surface of the bag just cleaned,
thereby maintaining a cake on the bag surface. The remainder
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falls into the hopper at the base of the baghouse and is
subsequently discharged.62'63
Most pulse-jet filters at MWI facilities use bag tubes that
are 10 to 15 cm (4 to 6 in.) in diameter and 1.8 to 5.8 m (6 to
19 ft) in length.59'62'64 The bags are usually arranged in rows
and are cleaned one row at a time in sequence. The preferred
method of cleaning initiation is based on pressure differential
with a timer override to prevent extended operation without
cleaning. Cleaning may alternately occur in a timed sequence.
3.2.3 Factors Affecting Performance
The performance of the fabric filter relative to PM, acid
gas, metals, and CDD/CDF emissions is affected by the fabric
filter design and operating parameters and also by key MWI
operating parameters. Key pulse-jet filter design and operating
parameters are the air-to-cloth ratio (or filtration velocity),
bag material, operating temperature, pressure drop across the
filter, and cleaning frequency. Key process parameters that can
affect fabric filter performance, particularly long-term
performance, are variations in temperature, flow rate, and
pollutant concentrations that result from the heterogeneous
nature of the MWI process. Process startup/shutdown procedures
can also affect long-term performance.
The air-to-cloth (A/C) ratio is actually a measure of the
superficial gas velocity through the filter medium. It is a
ratio of the flow rate of gas through the fabric filter (at
actual conditions) to the area of the bags and is usually
measured in units of m3/sec/m2 (acfm/ft2). Data obtained from
air pollution control device vendors indicate that pulse-jet
fabric filters for MWI's typically are designed with an air-to-
*2 ^
cloth ratio in the range of 0.008 to 0.02 nvVsec/m
(1.6 to 4.3 acfm/ft2) of bag area.59'61'64 Fabric filter systems
are designed to operate with as high an A/C ratio as feasible in
order to limit size and cost. However, in general, the lower the
A/C ratio, the lower the PM emission rate. Short-term exceedance
of the design ratio is not likely to have a substantial effect on
emissions. However, long-term exceedances will increase
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particle-phase emissions from bleed-through and have the
potential to cause bag failure through abrasive action. Under a
failure condition (e.g., tears at the collar or multiple pinhole
leaks) , emissions of PM and materials such as metals and CDD/CDF
attached to particles are likely to increase substantially. The
fabric filter should be designed with an A/C ratio based on the
maximum expected gas flow rate. Therefore, at lower gas flow
rates, the operating A/C ratio will be lower and the PM
collection performance would be expected to be the same or higher
than that at the design A/C ratio.
Bags vary with respect to type of construction and material
of construction. The three major types of construction are woven
bags, felted bags, and membranes: A wide variety of materials
have been used to construct bags. Usually both bag type and
material are selected based on a vendor's experience with systems
installed on comparable processes. Key factors that are
considered in making the selection are the cleaning method,
resistance of the material to abrasion and chemical attack,
expected operating temperature, and costs. For MWI's, both
fluctuating temperatures and resistance to acids are of concern.
The choice of bag material and construction can affect the
performance of the system in removing PM. Felted bags typically
are recommended in pulse-jet fabric filters controlling emissions
from MWI's. The relatively thick felt fabric provides maximum
particle impingement and collects PM more efficiently than woven
fabric at comparable gas velocities.65 Gore-Tex® membrane bags
can also be used to achieve low outlet PM loadings (i.e.,
22.5 mg/dscm [0.01 gr/dscf]).61 If felted bags are used,
synthetic materials that are temperature- and acid-resistant are
recommended. Vendor recommendations include acrylic, P-84
(Raster® Scrim), and Rylon®.60'61
The operating temperature of the fabric filter is critical
to the long-term performance of the system. The system must be
operated within a relatively narrow temperature range to prevent
bag failure due to chemical attack or temperature-driven
degradation. Because the exhaust gas from an MWI can contain
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HC1, the unit should be operated at temperatures sufficiently
high to ensure that no surface temperatures drop below the acid
dewpoint. Otherwise, condensation of HC1 will result in
corrosion of the housing or bags. The boiling point of HC1
(aqueous hydrochloric acid) is 110°C (230°F); gas temperatures
should be maintained at or above 120°C (250«F) to ensure that no
surfaces are cooled below the dewpoint. Each type of bag
material has a specified maximum recommended operating
temperature. If the system is operated at temperatures somewhat
higher than the maximum recommended operating temperature, bags
will degrade over time; operation at substantively higher
temperatures can cause bags to fail completely. Gas temperatures
should be within a temperature range bounded by the HC1 dewpoint
and the maximum recommended operating temperature for the
specific material to prevent bag failures and the attendant
increase in particle-phase emissions.
In addition to its importance in maintaining fabric filter
integrity, temperature can also directly influence the control of
acid gases, volatile metals, and CDD/CDF. All of the mechanisms
described earlier related to these pollutants are temperature
dependent. For all of the postulated mechanisms, improved
control is achieved with lower temperatures in the baghouse.
Consequently, the temperature should be maintained at as low a
level as possible, given the acid gas constraints described
above, to enhance control of these pollutants. Vendors suggest
an optimal temperature range of 120° to 150°C (250° to 300°F) to
achieve the best control in combined dry-injection/fabric
filtration systems.59"61'64
Pressure drop across fabric filters generally is maintained
within a narrow range by controlling the cleaning cycle of the
system. Pressure drops below the minimum indicate that either
leaks have developed or excessive cleaning is removing the base
cake from the bags. Either condition decrease performance
immediately. Pressure drops greater than the maximum indicate
that either bags are "blinding" or excessive cake is building on
the bags because of insufficient cleaning. Over time, high
71
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pressure drops lead to bag erosion and degradation and,
subsequently, to decreased performance. The pressure drop on MWI
systems generally is maintained in the range of 1.5 to 5 in.
w.c.59-61,64
As suggested by the above discussion, the fabric filter
cleaning cycle can have a significant impact on fabric filter
performance. Typically, one of two procedures is used to
determine a cleaning cycle. For the simpler of the two, vendor
engineers monitor facility operations carefully during equipment
shakedown. The pressure drop pattern is observed, and a timed
cleaning sequence is established to keep the pressure drop well
within acceptable limits. This timed cycle is then incorporated
into subsequent operating procedures. As an alternative, the
system can be equipped with a pressure drop sensor, and a control
loop can be used to initiate the cleaning cycle when the pressure
drop reaches a specified upper level. Either system can work
well, but a malfunction in either system or changes in the
process create performance problems. Too frequent cleaning can
cause the cake to deplete, resulting in an increase in emissions
of PM. On the other hand, cleaning that is too infrequent will
result in excessive cake buildup and an increased pressure drop
through the system. This latter scenario creates two potential
problems. If the pressure drop becomes too great, the system
will lose draft to the primary chamber of the MWI, and fugitive
emissions can be generated. The excessive cake buildup also
results in substantial increases in local gas velocities at some .
points in the bags. These increased velocities can generate an
immediate increase in emissions via particle seepage or bleed-
through and can result in increased abrasion that deteriorates
bag integrity.
The variations inherent in the operation of MWI's translate
into variations in gas stream characteristics including
temperature, flow rate, and pollutant concentrations. Of these
three gas stream characteristics, temperature is most critical.
All fabric filter control systems installed on MWI's incorporate
some type of gas-cooling system upstream of the filter. For
72
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those systems that do not have WHB's, the ability of these
cooling systems to respond to rapid temperature changes in the
combustor exhaust is a key to the long-term performance of the
fabric filter. If these systems do not cool the gas stream
properly, periodic temperature exceedances lead to bag
degradation and reduced collection efficiency.
Variations in the MWI exhaust gas flow rate are compensated
for by the proper design of the fabric filter system. The fabric
filter system should be designed with an A/C ratio based on the
maximum expected gas flow rate. Therefore, at lower gas flow
rates, the A/C ratio will be lower and the PM collection
performance would be expected to be the same or higher than that
at the design A/C ratio.
The PM loading and particle size distribution must be
considered during the design of a fabric filter and also during
operation; however, within certain limitations (±10 to 20 percent
of design values), changes in these parameters do not seriously
affect fabric filter efficiency.65 Nevertheless, an increase in
mass loading may require more frequent cleaning of the bags as a
result of faster filter cake buildup.65 A major advantage of a
properly designed fabric filter system is its ability to perfortn
well over the normal variation in MWI exhaust gas
characteristics.
3.3 DRY SCRUBBERS
This section describes the application of dry scrubbers to
MWI's. Dry scrubbing techniques that could be applied to MWI's .
can be grouped into two major categories: (1) dry sorbent
injection, and (2) spray dryer absorber systems. During the past
several years, many dry sorbent injection systems have been
installed on MWI's. Many spray dryer absorber systems have been
installed en municipal waste combustors (MWC's) but only one has
been installed on an MWI to date.
Dry scrubbers use an alkaline sorbent to react with and to
neutralize the acid gases in the MWI exhaust gas stream.
Additionally, activated carbon can be injected to control mercury
and CDD/CDF through adsorption. The reaction product is a dry
73
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solid that Is collected along with fly ash and any unreacted
sorbent in a PM control device such as a fabric filter, in MWI
applications, dry scrubbers are invariably'followed by a fabric
filter. The following paragraphs describe dry scrubbers and
their operation. Section 3.3.1 describes dry scrubbing
principles. Section 3.3.2 describes dry sorbent injection
systems. Section 3.3.3 describes spray dryer absorber systems.
3-3.1 Drv Scrubbing Principles
Dry sorbent injection systems use adsorption to control acid
gases while spray dryer absorbers use absorption and
adsorption.66 The addition of activated carbon also controls
mercury and CDD/CDF emissions through adsorption. The principles
of adsorption and absorption as applied to dry scrubbers are
briefly described below.
3.3.1.1 Adsorption. During adsorption, one or more gaseous
components are removed from an effluent gas stream by adhering to
the surface of a solid.67 The gas molecules being removed are
referred to as the adsorbate, while the solid adsorbing medium is
called the adsorbent.67 In dry injection systems, the adsorbents
or sorbents typically include a finely divided alkaline material
such as calcium hydroxide (hydrated lime), magnesium oxide, or
sodium bicarbonate. Activated carbon can be added for the
control of mercury and CDD/CDF.
Adsorption occurs in a series of three steps as illustrated
in Figure 19.68 In the first step, the contaminant diffuses from
the bulk area of the gas stream to the external surface of the
adsorbent particle.68 In the second step, the contaminant
molecule migrates from the relatively small area of the external
surface to the pores within each adsorbent particle.68 In the
third step, the contaminant molecule adheres to the surface of
the pore.68 in the dry sorbent injection system, the acid gas
molecules adsorb onto the surface of and react with the sorbent
particles (usually hydrated lime) to neutralize the acid gases by
forming neutral chemical salts.
Effective adsorption of acid gases, mercury, and CDD/CDF in
dry scrubber applications requires the following:
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1. A large interfacial surface area between the gas and the
sorbent;
2. Good mixing of the gas and sorbent phases;
3. Sufficient residence, or contact, time between the
phases for adsorption and subsequent neutralization to occur; and
4. Sufficient sorbent (type and amount) to adsorb and to
neutralize the acid gases and to adsorb mercury and CDD/CDF.
Adsorption of vapor-phase organic and metallic compounds
such as CDD/CDF and mercury also occurs in dry scrubber
applications, especially when activated carbon is injected. The
presence of a large interfacial contact area formed by the
activated carbon and the fine particles of the alkaline sorbent
provides numerous surface sites for condensation and/or
adsorption of these vapor-state compounds to occur. Turbulence
and adequate residence time also promote adsorption of these
compounds. The temperature of the gas stream must be low enough
to allow condensation of these compounds to occur but not so low
as to allow condensation of HC1 gas that causes corrosive
conditions. Additionally, the adsorption process may be enhanced
by the filter cake on the filter bags in a fabric filter.
3-3-1.2 Absorption. Section 3.1.1.2 described how gaseous
pollutants are absorbed in wet scrubber applications. Many of
the principles described there also apply to absorption in spray
dryer applications. Effective absorption of acid gases in spray
dryer applications requires the following:
1. A large interfacial contact area between the gas and
slurry droplets;
2. Good mixing of the gas and slurry droplets (i.e.,
turbulence), and
3. Sufficient residence, or contact, time between the
phases for absorption and subsequent neutralization to occur.
In the case of spray dryer absorber systems, the absorbing
medium is the liquid slurry droplets as opposed to the scrubbing
liquid used in packed-bed scrubbers. The acid gases are absorbed
into the droplets where they are neutralized by the lime in the
droplets. Subsequently, the liquid in the droplets is evaporated
76
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so that the" reaction products along with unreacted sorbents are
dried for collection in a PM control device. After the sorbent
has been dried, adsorption of unreacted acid gases and vaporous
metals and organics onto sorbent particles may occur as the dry
sorbent and exhaust gases pass to the PM collection device. This
adsorption process may be enhanced by the filter cake on the
filter bags in a fabric filter.
3.3.2 Dry Sorbfnt Injection
This section provides a general description of the dry
sorbent injection system including equipment components and gas
cleaning process followed by a discussion of the factors
affecting the performance of the system including key operating
and design parameters and gas stream characteristics.
3.3.2.1 General Description. A dry sorbent injection
system typically is comprised of the following components:
1. Sorbent storage/feed hopper;
2. Sorbent transport system;
3. Venturi/injector;
4. Reaction/expansion chamber (optional); and
5. Recycle system (optional).
Figure 20 illustrates a schematic of a dry injection system
showing the major components listed above with the exception of
the venturi and the recycle system. The following paragraphs
describe these components along with the dry injection system gas
cleaning process.
The dry injection scrubber uses injection of a dry, finely
divided alkaline sorbent such as calcium hydroxide (hydrated
lime), magnesium oxide, or sodium bicarbonate for the adsorption
of acid gases and powdered activated carbon for the adsorption of
mercury and CDD/CDF. The alkaline sorbent typically is stored in
a storage bin that also acts as a feed hopper for the system.
This bin may have a cone shaped bottom to direct the sorbent to a
rotary airlock, slide gate, or volumetric screw feeder that
meters sorbent into the pneumatic line that feeds the MWI exhaust
gas duct. The bin may also be equipped with a shaker mechanism
and/or a screw auger that help prevent clumping of the sorbent.
77
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The feeding' system typically is controlled by a microprocessor
system that controls the operation of the rotary airlock, slide
gate or screw feeder in some systems, the sorbent injection rate
is controlled by opening and closing the airlock. By controlling
the length of time and the number of times in a given time period
that the airlock or slide gate remains open, the sorbent
injection rate can be closely controlled. Other systems simply
feed sorbent on a continuous basis using a controller that
controls the speed of the screw feeder.
Typically, the sorbent is transported to the MWI exhaust gas
duct pneumatically. As the sorbent is metered into the pneumatic
line, a blower propels the sorbent through the line to the duct.
Additionally, the system's draft pulls the sorbent through the
line. The action of the blower and the system draft provides the
initial fluidization of the sorbent for transport to the duct.
Other, simpler systems use a gravitational feed approach instead
of a pneumatic system where the sorbent is fed through a vertical
pipe from a feed hopper located above the duct.
in many systems, the sorbent is injected into the duct
upstream of or at a venturi section of the duct. The purpose of
the venturi is to introduce turbulence to the gas stream and
sorbent, thereby providing good mixing and enhancing adsorption
of the acid gases.70'71 Some systems have an adjustable venturi
throat that compensates for the variations in the MWI exhaust gas
flow rate.
70
As in a wet venturi system, adjusting the venturi
maintains a constant gas velocity.across the throat, thereby
preventing the reagent from falling out in the duct.
in some dry injection systems, a reaction chamber (expansion
chamber) is included that allows increased residence time for
adsorption and neutralization to occur.70 One vendor utilizes a
specially designed heat exchanger that both cools the gases and
provides increased residence time.60 From the reaction chamber,
the gas stream, containing the entrained sorbent particles and
fly ash, is ducted to a fabric filter.
Some manufacturers include a sorbent recycle system that
recycles a portion of the collected sorbent/fly ash back to the
79
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sorbent injection system.71 The primary purpose of the recycle
stream is to increase reagent utilization and thereby reduce
overall sorbent costs.71 Recycle systems are installed on a
case-by-case basis based on the economics of the installation.
The buildup of a cake on the filter bags in the fabric
filter provides additional intimate contact between the gaseous
pollutants and sorbent for adsorption to occur. Emission test
data suggest that the fabric filter cake plays a role in
collecting HC1, volatile metals, and organic pollutants such as
CDD/CDF in combination dry sorbent injection/fabric filtration
systems.71'72 Additionally, specific tests suggest that HC1
control in such systems is related to cake build-up and depletion
and that volatile mercury and CDD/CDF control is improved when
activated carbon is used as a sorbent in the cake.72 Testing to
investigate the effectiveness of injecting activated carbon (in
addition to hydrated lime), in controlling both mercury and
CDD/CDF emissions across a dry sorbent injection/fabric filter
system, was conducted in September 1991. The results of this
test along with the results of the entire test program are
presented in Section 4.0 of this report.
3.3.2.2 Factors Affecting Performance. The performance of
the dry sorbent injection system relative to acid gas, metals,
and CDD/CDF emissions is affected by the dry injection system
design and operating variables in promoting adsorption of these
compounds and also by key MWI operating variables. Dry injection
systems control primarily acid gases by adsorption; metals and
CDD/CDF are also controlled by this mechanism but to a lesser
extent. While PM is not controlled by dry injection, a PM
control device located downstream of the dry injection system
collects flyash from the MWI along with the dry, solid reaction
product and any unreacted sorbent. The following paragraphs
describe the key dry injection system design and operating
variables that promote adsorption including sorbent fluidization
and particle size, retention/reaction time, stoichiometric ratio,
and gas stream moisture content and temperature. Additionally,
key process parameters that can affect dry injection system
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performance" are discussed including variations in gas stream
temperature, flow rate, and pollutant concentrations that result
from the heterogeneous nature of the MWI process.
Maintaining proper sorbent particle size and fluidization is
important in providing surface adsorption sites and in fully
utilizing the injected sorbent. The sorbent (typically hydrated
lime) has particle sizes that allow 90 percent by weight of the
material to pass through No. 325 mesh screens.71 This particle
*7 T
size range is approximately the consistency of talcum powder.
Sorbent particles in this size range provide sufficient total
alkaline sorbent surface area for effective adsorption to
occur.71 Larger particles have a smaller total surface area and
would require larger fan capacity .to fluidize the sorbent. The
dry injection fluidization system (transport blower) capacity
must be sufficient to fluidize the sorbent adequately. The
sorbent must be fluidized uniformly across the duct so that all
7P
portions of the gas stream are contacted by sorbent particles.
The use of a venturi constriction helps to provide the turbulent
conditions necessary for intimate contact between the gaseous
compounds and the surface of the particles.71 Insufficient
fluidization allows sorbent to fall out of the gas stream unused
and may ultimately lead to plugged lime feed pipes and/or MWI
exhaust gas ducts.
Adequate retention/reaction time is necessary for effective
adsorption of acid gases, metals, and CDD/CDF. Retention time in
dry injection systems is prolonged through the use of specially
designed reaction/retention chambers to provide intimate mixing
between the gas stream and sorbent particles. One vendor
supplies a specially designed heat exchanger both to extend the
retention time and to cool the gases. ° In some cases, an
extended duct is used to prolong retention time while other
systems compensate for a lack of retention time by operating the
system at a higher stoichiometric ratio or extending the
dirty-air side of the fabric filter.
The stoichiometric ratio is defined as the molar ratio of
calcium in the lime fed to the dry sorbent injection system to
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the theoretical amount of calcium required to completely react
with the HC1 and S02 in the MWI exhaust gas. Because of mass
transfer limitations, incomplete mixing, differing rates of
adsorption and reaction (SO2 reacts more slowly than HC1), and
the presence of other acid gases that react with the .calcium in
the lime (e.g, hydrogen fluoride, sulfur trioxide),
stoichiometric ratios in excess of 1:1 are required. Vendors
design dry injection systems with extended retention times to
operate at stoichiometric ratios of sorbent (hydrated lime) to
HC1 that range from 1.3:1 to 2:I.59'61'64 At such stoichiometric
ratios, these vendors guarantee HC1 reductions that range from 90
to 99 percent.59'61'64 Higher removal efficiencies can be
achieved by increasing the stoichiometric ratio.59'61'64
The gas stream moisture content and temperature are
important variables in achieving effective acid gas
neutralization. Some vendors recommend using evaporative coolers
both to humidify and to cool the gas stream.60'61'64 This
process increases the reagent activity.61 These evaporative
coolers may be used in conjunction with or without the use of a
WHB but typically are used when no WHB is present.60'61'64 Other
vendors use combinations of evaporative coolers and heat
exchangers or heat exchangers alone.59'64 The optimum
temperature for the neutralization of acid gases ranges from 121°
to 177°C (250° to 350°F) according to vendors.59"61'64 The lower
the temperature, the higher the HC1 and S02 removal.59
Additionally, one vendor reported that lower temperatures improve
the removal efficiency of lead, mercury, and CDD.59
The variations inherent in the operation of MWI's translate
into variations in gas stream characteristics including
temperature, flow rate, and pollutant concentrations. Because
dry sorbent injection systems are located after gas cooling
devices (WHB's, heat exchangers, or evaporative coolers) and
because these devices are designed to achieve a setpoint outlet
temperature, the effect of MWI exhaust gas temperature variation
is minimized. The optimum temperature for gaseous pollutant
removal in dry sorbent injection systems is approximately 12l°C
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(250°F). The boiling point of HC1 (aqueous hydrochloric acid) is
110°C (230°F); gas temperatures maintained at 121°C (250°F)
maximize gaseous pollutant removal and ensure that no surfaces
are cooled below the dewpoint. However, condensation of HC1 on
cool surfaces (resulting in corrosion of metal components) can
occur even when measured gas temperatures are greater than 121°C
(250°F), particularly on systems without insulation. Insulation
around ductwork and the dirty- and clean-air sides of the fabric
filter will minimize the condensation of HC1 on internal metal
components by preventing cold spots. Corrosion caused by
condensation of HC1 can occur on the clean side (clean air
plenum, outlet ductwork, and outlet stack) even though most of
the HC1 has been removed from the gas stream. Some combination
of insulation and/or corrosion resistant materials can be used to
reduce corrosion problems.
Variations in flow rate may cause problems with fluidization
of sorbent in the duct. Flow rate variations may be compensated
for by a variable speed fan that is tied to the incinerator
draft. Some systems have adjustable venturi constrictions that
maintain both a constant velocity across the venturi and
72
turbulent mixing as the flow rate changes.
Variations in pollutant concentrations in the MWI exhaust
gas are dependent primarily on waste composition. The
stoichiometric ratio typically is specified based on the maximum
expected HC1 concentration through the system. Therefore, as the
HC1 concentration varies up to the maximum amount, the
stoichiometric ratio of lime to the theoretical amount required
will remain high enough for effective HC1 removal. It is not
clear how variations in the concentrations of metals and organics
observed in MWI exhaust gas streams would impact the
effectiveness of the dry sorbent injection system in removing
these pollutants.
3.3.3 Spray Dryer Absorbers
This section provides a general description of a spray dryer
absorber system including equipment components and gas cleaning
process followed by a discussion of the factors affecting
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performance" of the system including key operating and design
parameters and gas stream characteristics.
3.3.3.1 General Description. A spray dryer absorber system
typically is comprised of the following components:
1. Sorbent preparation system;
- - storage
- - slaker
- - mixing tank
- - feed tank
2. Atomizers; and
3 . Spray dryer absorber vessel.73
The primary differences between a dry sorbent injection
system and a spray dryer absorber system are: (1) the physical
form of the alkaline sorbent and (2) the design of the system
used for contacting the sorbent with the acid gas stream.74 In a
dry sorbent injection system, the sorbent is dry while in a spray
dryer system, the sorbent is fed as an alkaline slurry. In a dry
sorbent injection system, the dry sorbent is injected into a duct
and may be followed by a reaction chamber while in a spray dryer
system, the wet slurry is atomized in a spray dryer absorber
vessel.
Figure 21 illustrates a spray dryer absorber. In this
system, the alkaline reagent, usually pebble lime, is prepared as
a slurry containing 5 to 20 percent by weight solids by slaking
the lime.73 Slaking is the addition of water to convert calcium
oxide to calcium hydroxide.76 Proper slaking conditions are
important to ensure that the resulting calcium hydroxide slurry
has the proper particle size distribution and that no coating of
the particles has occurred due to the precipitation of
contaminants in the slaking water.76 From the slaker, the slurry
passes to the mixing tank where the slurry is thoroughly mixed
before passing to the slurry feed tank.
The prepared slurry is atomized into the gas stream in a
large absorber vessel having a residence time of 6 to 20 seconds.
Atomization of the slurry is achieved through the use of:
(1) rotary atomizers or (2) air atomizing nozzles. Generally,
84
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only one rotary atomizer is included in a spray dryer absorber.
However, a few applications have as many as three rotary
atomizers.74
In rotary atomizers, a thin film of slurry is fed to the top
of the atomizer disk as it rotates at speeds of 10,000 to
17,000 revolutions per minute. These atomizers generate very
small slurry droplets having diameters in the range of
100 microns. The spray pattern is inherently broad due to the
geometry of the disk.77
High pressure air is used to provide the physical energy
required for droplet formation in nozzle-type atomizers. The
typical air pressures are 483 to 621 kPa (70 to 90 psig). Slurry
droplets in the range of 70 to 2'00 microns are generated. This
type of atomizer generally can operate over wider variations of
the gas flow rate than can be used in a rotary atomizer.
However, the nozzle atomizer does not have the slurry feed
turndown capability of the rotary atomizer. For these reasons,
different approaches must be taken when operating at varying
system loads.78
The shape of the scrubber vessel must be designed to take
into account the differences in the slurry spray pattern and the
time required for droplet evaporation for the two types of slurry
atomizers. The length-to-diameter ratio of a spray dryer
absorber vessel using rotary atomizers is much smaller than that
for absorber vessels using air atomizing nozzles.77
3.3.3.2 Factors Affecting Performance. The performance of
the spray dryer system relative to acid gas, metals, and CDD/CDF
emissions is affected by the spray dryer system design and
operating variables in promoting absorption of these compounds
and also by key MWI operating variables. Spray dryer systems
control primarily acid gases by absorption; metals and CDD/CDF
also are controlled by this mechanism but to a lesser extent.
While PM is not controlled by a spray dryer, a PM control device
collects fly ash from the MWI along with the dry, solid reaction
product and any unreacted sorbent. The following paragraphs
describe the key spray dryer system design and operating
86
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variables that promote absorption including stoichiometric ratio,
slurry droplet size, the approach-to-saturation and outlet gas
temperature, and retention/reaction time. Additionally, key
process parameters that can affect dry sorbent injection system
performance are discussed including variations in temperature,
flow rate, and pollutant concentrations that result from the
heterogeneous nature of the MWI process.
The stoichiometric ratio is defined as the molar ratio of
calcium in the lime slurry fed to the spray dryer to the
theoretical amount of calcium required to completely react with
the HC1 and S02 in the flue gas at the inlet to the spray
dryer 79 However, because of mass transfer limitations,
incomplete mixing, differing rates of reaction (S02 reacts more
slowly than HC1), and the presence of other acid gases that react
with calcium (e.g., hydrogen fluoride, sulfur trioxide), more
than the theoretical amount of lime is generally fed to the spray
dryer 79 Stoichiometric ratios in the 1.2 to 1.3 range can
reportedly achieve 90 to 95 percent removal of HC1 and HF and 60
80
to 85 percent removal of S02-
The slurry droplet size would be expected to affect the
performance of the spray dryer in removing acid gases, metals,
and CDD/CDF. Smaller droplet size increases the surface area for
adsorption and reaction between lime and acid gases and increases
the rate of water evaporation.79 Additionally, it is important
that all of the slurry droplets evaporate to dryness prior to
approaching the absorber vessel side walls and prior to exiting
the absorber with the gas stream.77 Accumulations of material on
the side walls or at the-bottom of the absorber would necessitate
an outage since these deposits would further impede drying.
Proper drying of the slurry requires generation of small slurry
droplets and adequate mixing with the hot flue gases.
Drying that is too rapid can reduce pollutant collection
efficiency since the primary removal mechanism is absorption into
the droplets.77 There must be sufficient contact time for ^
absorption to occur and for the slurry to evaporate to dryness.
For this reason, spray dryer absorbers controlling MWC's are
87
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operated with an approach-to-saturation range of 32° to 82 °C
77
(90'
77
to 180°F). The approach-to-saturation is the difference
between the wet bulb and dry bulb temperatures measured by wet
and dry bulb monitors at the outlet of the spray dryer vessel
An increase in the approach-to-saturation is sensed by the
automatic control system that quickly reduces the slurry feed
rate.81
The spray dryer outlet temperature is controlled by the
amount of water in the slurry. More effective acid gas removal
occurs at lower temperatures, but the temperature must be kept
high enough to ensure that the slurry and reaction products are
adequately dried prior to collection in the fabric filter. In
addition, a minimum spray dryer absorber vessel outlet
temperature of approximately 240°F is required to control
agglomeration of PM.79
In MWC applications, the amount of lime fed is generally
controlled by one of two means. In one approach, the lime-slurry
feed rate is controlled by an acid gas analyzer/controller
(generally based on S02 or HC1 emissions) at the stack. As the
outlet acid gas concentration increases or decreases, the lime-
slurry feed rate is accordingly raised or lowered, respectively,
to maintain a specified outlet, acid gas concentration. The
second approach uses a constant lime-slurry feed rate that is
sufficient to react with peak expected acid gas concentrations.79
For effective absorption of gaseous pollutants to occur,
adequate retention/reaction time is required. The retention time
in spray dryers is determined by the size of the spray dryer
absorber vessel. Retention times in spray dryers controlling
emissions from MWC's range from 10 to 15 seconds.80
The variations inherent in the operation of MWI's translate
into variations in gas stream characteristics including
temperature, flow rate, and pollutant concentrations. For those
systems equipped with a WHB or heat exchanger, the variation in
the MWI exhaust gas temperature is damped. The spray dryer
outlet flue gas temperature is controlled at levels well above
its saturation value by controlling the amount of water in the
88
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slurry. This control precludes any sorbent from contacting
downstream surfaces as a wet powder leading to solids buildup.
It also assures operation well above the dew points of any acid
gases. Because of the presence of calcium chloride (a very
hygroscopic, difficult-to-dry solid), temperatures are typically
controlled at 110° to 160°C (230° to 320°F) by limiting the
amount of water injected.
82
Flow rate variations may be compensated for by a variable
speed ID fan that is tied to the incinerator draft.
Variations in pollutant concentrations in the MWI exhaust
gas are dependent primarily on waste composition. A second
control loop can be provided based on the pollutant emission
levels in stack gases to regulate the addition of reagent to the
system. In many cases, the sorbent rate is fixed at a
conservatively high rate to ensure low stack emissions, but waste
disposal plus sorbent operating costs are increased.82
4.0 PERFORMANCE OF EMISSION CONTROL MEASURES
One component of the background information development for
MWI's was a comprehensive emission test program. The program
generated emission test data on a wide variety of pollutants
including all of those for which emission limits are to be
established (PM, CO, HC1, SO2, NOX, CDD/CDF, Cd, Pb, and Hg).
These test data provide information on the effects of combustion
system operating parameters on emissions and on the performance
capabilities of add-on APCS's. This section summarizes the
results of the test program. Section 4.1 briefly describes the
test program and facilities tested and presents a summary of the
test data. Section 4.2 presents a discussion of the test results
including a comparison of the emission results obtained when
incinerating different waste types, a discussion of the effects
of combustion control parameters on emissions, and a discussion
of the performance of four APCS's--a combination dry injection
fabric filter (DI/FF), a combination venturi scrubber/packed-bed
scrubber (VS/PB), a fabric filter "in series with a packed-bed
scrubber (FF/PB), and a spray dryer/fabric filter combination
(SD/FF)--with respect to PM, HC1, CDD/CDF, and metals emissions.
89
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Note that tests on the DI/FF and SD/FF systems were performed
with and without activated carbon injection. Section 4.3
presents demonstrated emission control levels (i.e., emission
limits) associated with each of the emission control techniques
described above.
4.1 TEST PROGRAM SUMMARY
4.1.1 Facility and Test- Condition Descriptions
The emissions test program generally consisted of triplicate
test runs under multiple sets of operating conditions at seven
MWI facilities, which are denoted herein by the letters A, B, J,
K, M, S, and W. At the four facilities equipped with add-on
APCS's (A, B, J, and M) , simultaneous measurements were made at .
the APCS inlet and outlet for PM, HC1, S02/ CDD/CDF, and metals.
Operating parameters that were, varied to achieve different
operating conditions included waste feed type, waste feed
charging mode, and secondary chamber temperatures. Table l
provides a summary of the test conditions and the test program
conducted at each facility, including the test condition numbers,
the ,aste type charged, the target waste charge rates, and the
target secondary/tertiary chamber temperatures.
Summary tables for the incinerator and APCS operating data
collected from the test program are included in Appendix A.
Table A-l presents pertinent incinerator operating data for each
of the 25 test conditions (77 test runs) that were conducted as a
part of this program, and Tables A-2 through A-5 present
pertinent APCS operating data for those facilities with add-on
APCS's. The paragraphs below briefly describe the systems at
each of the seven facilities tested and the general structure of
the test program at each site; more detailed descriptions of the
Q *1 _ Q A
facilities are included in the individual test reports.
4.1.1.1 Facility A. The incineration unit at Facility A is
a Cleaver-Brooks Model 780-A/31 intermittent-duty MWI with three
combustion chambers. The primary chamber operates at starved-air
levels, while the secondary and tertiary chambers operate with
excess air. The nameplate charging capacity of the unit is
295 kg/hr (650 Ib/hr) at an assumed waste heating value of
90
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TABLE 1 MATRIX OF TEST CONDITIONS FOR TESTS CONDUCTED
AT EACH FACILITY
Target tertiary/
secondary chamber
temp.. °F
Target waste charge
rate, Ib/hr
^500 - general medical waste generated at a 500-bed hospital
G100 - general medical waste generated at a 100-bed hospital
RB - red bag waste
General - general medical waste
Pathological - pathological waste
**At facility J, the target charge rate was 750 Ib/batch.
cAt facility J, test condition 2 refers to testing during the bumdown phase of the batch where test
condition 1 was conducted during the burn phase.
dSame hourly charge rate as test condition 2 but larger charges were charged less frequently.
91
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19,800 kJ/kg (8,500 Btu/lb) . The facility is equipped with a WHB
for energy recovery and a DI/FF APCS.
Two separate test sequences were conducted at Facility A.
During the first sequence, emissions were measured simultaneously
at the DI/FF inlet and outlet under seven sets of test conditions
based on waste feed type and tertiary chamber operating
temperature. The target operating characteristics for these test
conditions were: Condition 1--general medical waste from a
500 bed hospital (G500) at a tertiary chamber temperature of
980°C (1800°F); Condition 2--G500 waste at 870°C (1600°F);
Condition 3--G500 waste at 1090°C (2000°F); Condition 4--general
medical waste from a 100 bed hospital (G100) at 980°C (1800°F);
Condition 5--red bag waste from a 500 bed hospital (RB) at 870°C
(1600°F); Condition 6--RB waste at 980°C (1800°F); and
Condition 7--RB waste at 1090°C (2000°F).
The second test sequence was designed to evaluate the effect
of activated carbon injection on DI/FF performance. During the
second test sequence, emissions were measured simultaneously at
the DI/FF inlet and outlet. The incinerator operating target was
identical to Condition 1 above and the DI/FF system was operated
at three carbon levels — none (Condition 1A) , 0.45 kg/hr (1 Ib/hr)
(Condition 8), and 1.14 kg/hr (2.5 Ib/hr) (Condition 9). The
actual incinerator operating parameters for all test runs within
both test sequences are presented in Table A-l while the actual
DI/FF operating parameters are presented in Table A-2.
4.1.1.2 Facility B. The incinerator at Facility B is a
Basic Environmental Engineering, Inc., Model 1500 continuous-duty
MWI with both secondary and tertiary chambers and a WHB. The
primary chamber of this unit operates at near stoichiometric
conditions, while the secondary and tertiary chambers operate at
excess-air conditions. The nameplate charging capacity of this
MWI is approximately 680 kg/hr (1,500 Ib/hr) of medical waste
with an assumed heating value of 19,800 kJ/kg (8,500 Btu/lb).
This MWI is equipped with an Andersen 2000, Inc., venturi
scrubber followed by two packed-bed scrubbers in series. The two
packed-bed scrubbers were installed in series because space
92
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limitations" prevented the installation of a single packed-bed
scrubber of suitable size. Emissions were measured at the inlet
and outlet of the APCS at one test condition: burning general
medical waste from the hospital at a nominal secondary chamber
temperature of 980°C (1800°F) .. The actual Facility B operating
parameter values for each test are included in Table A-l, and the
APCS operating parameter values for each test are presented in
Table A-3.
4.1.1.3 Facility J. The incinerator at Facility J is a
Simonds Model 2151B batch-duty MWI with two combustion chambers.
This unit has a nominal capacity of 340 kg/batch (750 Ib/batch)
at an assumed heating value of 22,400 kJ/kg (9,600 Btu/lb).
After a batch is charged to the primary chamber, the unit is
sealed and completes an operating cycle with three components--a
low-air phase (burn phase), a high-air phase (burndown phase),
and a cooldown phase. The unit is equipped with an APCS
comprising an air-to-air heat exchanger, and a FF/PB. Emissions
measurements were obtained during each of the first two
components of the operating cycle. Simultaneous measurements
were made upstream from the heat exchanger and downstream from
the FF/PB under one set of test conditions considered to
represent normal operating conditions for the facility. Separate
tests were conducted during two components of the operating
cycle--the low-air phase (Condition 1) and the high-air phase
(Condition 2). Limited CEM data were also collected during the
cooldown phase of the process. The values for the incinerator
operating parameters for the six test runs are included in
Table A-l, and APCS operating data for facility J are presented
in Table A-4. The incinerator was charged with general medical
wastes for these tests. Note that although only one test
condition was used at Facility J, the manual test data are
separated into two conditions that represent the low-air and
high-air components of the process cycle, respectively.
4.1.1.4 Facility K. The incineration unit at Facility K is
an Environmental Control Products (now Joy Energy Systems) Model
480-E intermittent-duty, dual-chamber MWI. The unit nominally
93
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operates at' starved-air conditions in the primary chamber and
excess-air conditions in the secondary chamber. It has a
charging capacity of 145 kg/hr (320 Ib/hr) at an assumed heating
value of 19,800 kJ/kg (8,500 Btu/lb). The unit is not equipped
with an APCS. ' **
The emission test program at Facility K included a total of
eight test runs under three different test conditions defined by
charging characteristics and secondary chamber temperatures.
Condition 1 consisted of frequent charges at less than design
feed rates. For Condition 1, waste was charged approximately
every 6 minutes at 9.1 kg (20 lb') per charge for an average feed
rate of 91 kg/hr (200 Ib/hr). Condition 2 represents the unit's
design feed rate with frequent charges. For Condition 2, the
nominal charging conditions were to charge 14 kg (30 lb) of waste
every 6 minutes for a total charging rate of 140 kg/hr
(300 Ib/hr). Condition 3 represents the unit's design feed rate
with infrequent charges. For Condition 3, plans called for
charging 140 kg/hr (300 Ib/hr) waste in 23 kg (50 lb) batches
every 10 minutes. During all three conditions, general medical
waste was charged to the unit. The target secondary chamber
temperatures were 1040°C (1900°F) during Conditions 1 and 2 and
870°C (1600°F) during Condition 3.
4.1.1.5 Facility M. The incineration system at Facility M
was custom designed and sized by ThermAll, Inc. The primary
components of the system are a rotary kiln, which is also called
the primary combustion chamber, followed by a fixed secondary
combustion chamber. The system is equipped with a WHB. The
system is designed with a heat input rate of 10.5 x 106 kJ/hr
(10 x 106 Btu/hr), which corresponds to a feed capacity of
454 kg/hr (1,000 Ib/hr) at an assumed waste feed heating value of
21,000 kJ/kg (10,000 Btu/lb). Currently, the system is limited
to a feed rate 'of 354 kg/hr (780 Ib/hr) (permit limit) and at
that level, the rotary kiln is designed to operate at
stoichiometric conditions. The APCS at Facility M comprises a
spray dryer followed by a pulse-jet fabric filter (SD/FF).
94
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The test program at Facility M comprised three runs at each
of two sets of test conditions. The incinerator operating
conditions were identical for both conditions with the charge
rate maintained at about 354 kg/hr (780 Ib/hr) and a secondary
chamber set point maintained at 982'C (1800°F) . The exhaust gas
temperature from the rotary kiln or primary chamber was typically
about 780°C (1450°F). During both conditions, general medical
waste was charged to the unit. The primary difference between
the two conditions was that, during the second condition,
approximately 1.1 kg/hr (2.5 Ib/hr) activated carbon was added to
the lime slurry to treat the exhaust gas.
4116 T^rilitv S. The incinerator at Facility S is a
Consumat Model C-75P intermit tent -duty, dual -chamber MWI. This
unit is designed to fire either general medical waste or
100 percent pathological waste. When general waste is fired, the
unit is designed to operate at starved- air conditions in the
primary chamber and excess-air conditions in the secondary
chamber. The unit operates with excess-air conditions in both
chambers when pathological waste is being fired. The nominal
charge capacity is 80 kg/hr (175 Ib/hr) for pathological waste
and 110 kg/hr (250 Ib/hr) for general medical waste. These
charge capacities are based on a heating value of 2,300 kJ/kg
(1,000 BTU/lb) for pathological waste and a heating value of
ig'.SOO kJ/kg (8,500 Btu/lb) for general medical waste. This
facility has ho APCS.
Emissions were measured at the Facility S secondary chamber
exhaust under three test conditions defined by waste type, waste
charging rate, and secondary chamber temperature. Plans for
Condition 1 called for 45 kg/hr (100 Ib/hr) pathological waste,
which is below design capacity, to be charged in equal charges at
15 -minute intervals. During Condition 2, pathological waste was
to be charged at 73 kg/hr (160 Ib/hr) in equal charges at
15 -minute intervals. For Condition 3, general medical waste was
to be charged at 73 kg/hr (160 Ib/hr) in equal charges at
15 -minute intervals. Target secondary chamber temperatures were
870°C (1600-P) for Conditions 2 and 3 and 1040 °C <1900«P) for
95
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Condition l". Note that for all runs actual secondary chamber
temperatures are substantially below target values. The
relatively high primary chamber temperatures suggest that
substantial waste combustion occurred there, and under such
conditions, the secondary burner appeared to have insufficient
capacity to maintain the target temperatures.
4.1.1.7 Facility W. The Facility W incinerator is an
Environmental Control Products (now Joy Energy Systems) Model-
480 E/SR-12H intermittent-duty, dual-chamber MWI. it is designed
to operate at starved-air levels in the primary chamber and
excess-air levels in the secondary chamber. The unit has a
charge rating of 175 kg/hr (385 Ib/hr) at an assumed heating
value of 19,800 kJ/kg (8,500 Btu/lb). This facility has no APCS.
The test program at Facility W involved three sets of test
conditions defined by charging practices and secondary chamber
temperature. Measurements were made at the secondary chamber
exhaust while general medical waste was charged to the unit. The
planned levels for Condition 1, which represents below design
feed rates with frequent charges and high secondary chamber
temperatures, were a charge rate of 90 kg/hr (200 Ib/hr) with
equal charges at 6-min intervals and a secondary chamber
temperature of 1040°C (1900°P). For Condition 2, which
represents design feed rate with frequent charges and high
secondary chamber temperatures, the charge rate was increased to
136 kg/hr (300 Ib/hr) with the same charging frequency and
secondary chamber temperature as Condition 1. For Condition 3,
which represents design feed rate with infrequent charges and low
secondary chamber temperatures, the average charging rate was
maintained at 136 kg/hr (300 Ib/hr), but the frequency was
changed to 10-min intervals and the secondary chamber temperature
was decreased to 870°C (1600°F). For all conditions; general
medical waste was charged to the unit.
4-1.2 Test Data Summary
The emission test program generated data on a wide variety
of pollutants for 25 test conditions (77 separate test runs) at
the seven sites. As described above, emissions measurements were
96
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made downstream from the secondary chamber and/or WHB ("post-
combustion" emissions) at all sites; measurements also were made
downstream of an APCS ("post-APCS" emissions)'at four sites.
Table 2 presents average post-combustion and post-APCS emission
concentrations by facility and test condition. For those
pollutants expected to be affected by add-on APCS's, Table 2 also
presents removal efficiencies based on mass emission rates.
Tables B-l and B-2 in Appendix B present post-combustion emission
data in concentration units corrected to a uniform excess air
level (7 percent 02) for each test run conducted at the seven
sites. Table B-l presents data on PM, CO, HC1, S02, and NOX
emissions, while Table B-2 presents data on CDD/CDF, Cd, Pb, and
Hg emissions. These data are presented with a mixture of English
and SI units in accordance with most common usage.
Graphical summaries of post-combustion emissions
concentrations are presented in Appendix C for PM (Figure C-l),
CO (Figure C-2), HC1 (Figure C-3), S02 (Figure C-4), NOX
(Figure C-5), CDD/CDF (Figure C-6), Cd (Figure C-7), Pb
(Figure C-8), and Hg (Figure C-9). Each of the graphs displays a
substantial amount of information about the distribution of
emission concentrations separately for each test condition. The
concentration levels for each individual test run are indicated
by the symbol '*' on each graph. In each graph and for each test
condition, the range of emissions is shown along with a small bar
in the range that denotes the average emission concentration.
Post-APCS emission concentrations corrected to a uniform
excess air level (7 percent 02) for PM, HC1, CDD/CDF, Cd, Pb, and
Hg for each test run are presented in Table B-3. Table B-3 also
presents APCS removal efficiencies based on mass emission rates
for those runs for which data were sufficient to permit
calculations. Appendix D provides graphical summaries for the
post-APCS emissions concentrations for those pollutants that are
expected to be affected by the add-on APCS's. These graphs,
which are analogous to those presented in Appendix C for post-
combustion pollutant concentrations are presented for PM
(Figure D-l), HC1 (Figure D-2), S02 (Figure D-3), CDD/CDF
97
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(Figure D-4) , Cd (Figure D-5), Pb (Figure D-6), and Hg (Figure
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4.2 DISCUSSION OF THE TEST RESULTS
This section summarizes general findings based on an
examination of the MWI and APCS operating parameters and emission
test data. Substantial insight about the performance of the
combustion systems and add-on APCS's tested can be gained by a
careful examination of the information presented in Table 2 and
Appendices B through D.
Table 2 presents emission concentrations for PM, CO, HC1,
S02, NOX/ CDD/CDF, and three metals. With the exception of CO
and NOX, emissions of each of these pollutants can be affected
substantially by waste characteristics. Emissions of four of the
pollutants--PM, CO, CDD/CDF, and to a lesser extent, N0x--are
likely to be affected by the combustion system characteristics.
Section 4.2.1 discusses the effects of waste types on post-
combustion emissions. In particular, emissions measured for test
conditions burning red bag waste and general medical waste are
compared and emissions measured for test conditions burning
pathological waste and general medical waste are compared.
Section 4.2.2 discusses the effects of variations in combustion
parameters on measured emissions. First, the relationships of
CDD/CDF emissions to CO and PM emissions are discussed. Second,
the relationships between emissions of CDD/CDF, CO, and PM and
combustion process parameters are discussed. In Section 4.2.3,
the variations in CO and THC emissions during the
burndown/cooldown phases of the batch and the intermittent MWI
operating cycles are described. In Section 4.2.4, the operating
cycle of batch MWI's is discussed. In Section 4.2.5, the effect
of combustion parameters on metals partitioning is described.
Finally, Section 4.2.6 presents a discussion of the performance
of the four APCS's: DI/FF, SD/FF, VS/PB, and FF/PB.
4.2.1 Effects of Waste Types on Emissions
The test programs conducted at Facilities A and S were
designed to evaluate the effect of different waste types on
emissions. The test program at Facility A was designed to
100
-------
characterize emissions during combustion of two general medical
wastes, (general waste from a 500-bed hospital [G500] and general
waste from a 100-bed hospital [G100]), and red bag infectious
wastes. The test program at Facility S was designed to compare
emissions from the combustion of pathological waste and general
waste.
4.2.1.1 Emissions from Combustion of General Medical Waste
Versus Red Baa Waste. In general, emission concentrations at
Facility A showed substantial overlap between general waste runs
and red bag runs. Neither waste type produced substantially
greater emissions for the pollutants measured. Additionally, for
the pollutants most likely to be affected only by waste
characteristics and not combustion conditions (HC1, S02, and
metals), the concentrations associated with red bag waste
generally are within the ranges obtained when general waste was
fired at Facility A and the other four intermittent-duty units.
The results of this test program indicate that uncontrolled
emissions from the combustion of red bag and general medical
waste are comparable.
While the emissions from red bag and general waste
combustion are generally comparable, two additional observations
(one related to Hg and one related to HC1) on the red bag/general
waste comparison at Facility A are noted below. The principal
difference in emissions resulting from burning red bag and
general waste at Facility A is in the Hg emissions. Figure 22
shows the effects of waste type on emissions of Hg at Facility A.
As indicated in Figure 22, Hg emissions from burning G100 (waste
obtained from another hospital) are one to two orders of
magnitude lower than Hg emissions measured while burning G500 and
red bag wastes. Also, with the exception of the first run of
test condition 6 (RB at 1800°F), the Hg concentrations associated
with burning G500 waste are higher than those from burning red
bag waste. Figure 23 compares the Hg concentrations measured at
Facility A with the Hg concentrations measured at other
facilities. The Hg concentrations found during the G500 (general
medical waste) runs at Facility A are substantially higher than
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those typically found at other facilities burning general medical
waste. Although the source of the Hg in the Facility A waste has
not been identified, the data indicate that the general waste
stream at Facility A has an Hg source that differs from those at
the other facilities tested. Overall, these data indicate that
Hg emissions may vary substantially from facility to facility and
between waste types, with neither RB nor general medical waste
consistently having higher Hg emissions.
Figure 24 shows the effects of waste type on emissions of
HC1 at Facility A. It is clear from Figure 24 that HC1
concentrations measured during two of the three test condition 7
runs (RB at 2000°F) were substantially higher than those during
the other red bag runs. These higher concentrations are the
result of spiking hexachlorobenzene as a cytotoxic surrogate
during these runs and are not attributed to the red bag wastes.
Additionally, two general waste runs (test condition 3, run
number 2 and test condition 8,,run number 1) had HC1
concentrations somewhat higher than the other general waste runs.
However, no differences in waste feed conditions were noted
during these runs, and the increased HC1 concentrations for these
runs are assumed to be attributable to normal waste variability.
4.2.1.2 Emissions from Combustion of General Medical Waste
Versus Pathological Waste. Table 3 presents the post-combustion
emissions measured at Facility S during the combustion of general
and pathological wastes. At Facility S, for the majority of
pollutants (PM, CO, HC1, CDD/CDF, and Pb), the emissions from the
pathological waste runs were substantially less (often as much as
an order of magnitude less) than those from general waste
combustion. The emission characteristics for the other
pollutants were more varied as described below.
The concentrations of Cd emissions were generally lower for
pathological runs than for general waste runs. The lone
exception was test condition 1, run no. 3, which had a Cd
concentration (504 fig/dscm at 7 percent 02) that was more than an
order of magnitude higher than the next highest concentration
(26 /jg/dscm at 7 percent O2) from the pathological runs. A
104
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review of the charging records provided no indication that the
wastes used for this run were different from those used for the
other pathological runs.
The Hg concentrations from three pathological runs and one
general waste run at Facility S were below the detection limit.
The other two general waste runs had concentrations of 10 ng/dscm
at 7 percent 02 or less. However, two of the pathological runs
(10 and 5) had Hg concentrations of 116 and 182 jtg/dscm at
7 percent O2, respectively. Review of test records provided no
additional information that could explain the higher levels.
Consequently, they are assumed to be within the normal range of
Hg emissions from combustion of pathological waste. Mercury
emissions from the combustion of pathological waste are low in
comparison to test runs conducted at other facilities where
general medical waste and red bag waste were combusted.
Additionally, Hg emissions from the combustion of general medical
waste at Facility S were significantly lower than the Hg
emissions measured at other facilities. Overall, Hg emissions
from Facility S during combustion of pathological waste and
general medical waste fall into the low end of the range of Hg
emissions measured from all facilities during this test program.
The two pollutants that showed consistently higher
concentrations when pathological wastes were burned than when
general wastes were burned at Facility S are NOX and S02. A
significant amount of heat input to the primary chamber from
auxiliary fuel is required during the combustion of pathological
waste. Because pathological waste combustion requires the use of
substantially more natural gas than the combustion of general
waste, the higher NOX concentrations are not unexpected.
Initially, the higher SO2 levels were somewhat surprising.
However, a review of the biological literature suggest that the
sulfur level in pathological tissue is high enough to explain the
S02 concentrations found at Facility S.91 Consequently, both the
NOX and S02 concentrations found at Facility S are assumed to be
reasonable uncontrolled levels for pathological waste combustion.
Overall, the waste-related pollutant emissions from pathological
107
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wastes are significantly lower than from general medical wastes.
The figures in Appendix C provide a comparison of Facility S data
with data from all of the other tests.
4.2.2 Effects of Combustion Controls
A wide variety of combustion control measures were described
in Section 2.2 As a part of the test program, two of those
parameters--waste feed rate and secondary chamber temperature--
were varied intentionally between different test conditions.
Additionally, facilities with different design secondary chamber
residence times were selected for testing. Variations in primary
chamber temperature and combustion air rates as indicated by
excess air levels were monitored during each test run. The post-
combustion emission data were analyzed to assess the effects of
variation in these combustion parameters on PM, CO, and CDD/CDF
emissions. These pollutants were selected because they are the
pollutants most likely to be affected by combustion controls.
The subsections below summarize the results of these
analyses. First, the interrelationships among CO, PM, and
CDD/CDF emissions are described. Then, the relationships among
emissions of each of these three pollutants and combustion
process parameters are discussed.
Initial examination of the data in Table 2 suggest that the
batch unit at Facility J operates quite differently than the
other units tested and that emissions for the Facility S
pathological waste combustion were different than those for the
Facility S general waste condition. Because of these
differences, analyses of combustion controls and PM, CO, and
CDD/CDF emissions were conducted using only the data from
continuous and intermittent units firing general waste.
4.2.2.1 Relationship of CDD/CDF to PM and CO Emissions.
One of the goals of the data analysis was to determine whether
relationships between emissions of CDD/CDF and CO and between
emissions of CDD/CDF and PM could be established. If strong
relationships between these pollutants exist, then CO and/or PM
could be used as surrogates for CDD/CDF emissions. The results
show that, overall, the relationship between CDD/CDF and CO is
108
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strong over" the full range of data and that large (order of
magnitude) changes in CO are indicative of changes in CDD/CDF
emissions. However, small changes in CO at low CO levels are not
related to changes in CDD/CDF emissions. These results are
described in more detail below.
Examination of the complete set of test data from continuous
and intermittent units showed CDD/CDF emissions to be strongly
related to both CO and PM emissions. Figures 25 and 26 show
plots on a log-log scale of CDD/CDF versus CO and PM,
respectively. Note that these plots suggest a nearly linear
relationship on a log-log scale between CDD/CDF emissions and
both PM and CO emissions over the full range of the test data.
This visual observation is confirmed by the estimated
correlations among the data which yield correlation coefficients
of 0.74 between the logs of CDD/CDF and PM and 0.85 between the
logs of CDD/CDF and CO.
While these results suggest reasonably strong relationships,
further insight into the relationships can be obtained by looking
at several subsets of the data. First, the data are divided into
two groups--those from newer facilities with better overall
combustion control measures (A, B, and W) and those from older
facilities (S and K). The results for the two groups are quite
different. For the newer facilities a strong correlation (0.90)
between the logs of CDD/CDF and CO still exists, but the
correlation between the logs of CDD/CDF and PM is substantially
weaker (0.55). However, for older facilities both correlations .
remain strong (0.90 for PM and 0.93 for CO).
On balance, these data show a strong relationship between
CDD/CDF and CO over a wide range of emissions represented by the
test data as a whole. However, the results should be interpreted
cautiously for any smaller range of data. Examination of the
relationship between the logs of CDD/CDF and CO at Facility A,
which has emissions at the low end of the emission ranges, showed
essentially no relationship between CO concentrations and CDD/CDF
emissions.
109
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100000
jf 10000
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• 100
1000
10000
M**n CO Dry (ppnrtv) {ft 7% O2)
Figure 25. Relationship between CDD/CDF and CO emissions,
100000
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1000
100
0.01
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0.10
1.00
(•! 7% O2)
Figure 26. Relationship between CDD/CDF and PM emissions,
110
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Taken"together, the data suggest quite different
interpretations, depending on the magnitude of changes in CO
levels. Large (order of magnitude) changes in CO concentrations
appear to be indicative of changes in CDD/CDF emissions.
However, because small changes in CO concentrations at low levels
such as those found at Facility A are not related to changes in
CDD/CDF emissions, CO does not provide a good surrogate for
CDD/CDF emissions at low concentrations.
4.2.2.2 Effect of Combustion Parameters on PM. CO. and
rnryrnF Emissions. The three pollutants that are most affected
by combustion control parameters are PM, CO, and CDD/CDF. In
developing the matrix of test conditions for this test program,
several combustion control parameters were considered potentially
to have an impact on emissions of PM, CO, and CDD/CDF. These
parameters include secondary/tertiary chamber residence time,
secondary/tertiary chamber temperature, primary chamber
temperature, and waste charge rate. One of the goals of the test
program was to measure the impact of as many of these parameters
as possible on emissions by selecting MWI facilities and test
conditions that would allow the appropriate comparisons of
emission results to be made. The evaluation of the effect of
combustion parameters on measured emissions are presented in two
sections. The effects of variations in the secondary/tertiary
combustion chamber control parameters--secondary/tertiary chamber
temperature and secondary/tertiary chamber gas residence time-on
emissions are discussed in Section 4.2.2.2.1. The effects of
variations in the primary combustion chamber control
parameters--primary chamber temperature and waste charging
procedures--on emissions are discussed in Section 4.2.2.2.2.
4.2.2.2.1. Secondarv/tertiarv rhamber combustion control
parameters. In the secondary/tertiary chambers of MWI's,
combustion gases from the primary chamber containing volatiles
are further combusted under excess-air conditions. Effective
combustion in the secondary/tertiary chambers is accomplished
when sufficiently high temperatures are attained, turbulent
conditions are achieved in the presence of sufficient oxygen
ill
-------
(good mixing of combustion air with volatiles) , and sufficient
residence time at high temperature is allowed. Because all MWI's
are designed to operate the secondary/tertiary chambers in an
excess-air mode and because all MWI's incorporate secondary
chamber designs that introduce some degree of turbulent mixing
between combustion air and primary chamber exhaust gases, the
focus of the test program was to select MWI facilities with
specific features, to operate them at specified conditions, and
to measure post-combust ion emissions to determine the impact of
secondary/tertiary chamber temperature and residence time on
emissions. This section first summarizes the variations in
secondary/tertiary combustion control parameters integrated into'
the test program design and subsequently presents an evaluation
of the emission results with respect to these combustion control
parameters.
Testing conducted at Facilities A, W, and K included test
conditions where general medical waste was charged to the MWI and
target secondary/tertiary chamber temperatures were 870°C
(1600°F) and 980° to 1040°C (1800° to 1900°F). (Facility A also
included a test condition where general medical waste was charged
and the target secondary/tertiary chamber temperature was 1090°C
[2000°F].) At Facilities B and M, testing comprised charging
general medical waste with a target secondary/tertiary chamber
temperature of 980°C (1800°F). Testing at Facility S included
one test condition where general medical waste was charged and
the target secondary/tertiary chamber temperature was 870°C
(1600°F). These MWI facilities were selected for testing in part
because they had different design secondary/tertiary chamber
residence times. Facility A has a design secondary/tertiary
chamber residence time of 1.34 seconds at 1800°F. The design
secondary chamber residence time at Facility W is 1.0 second;
Facility K is 0.33 second; Facility B is 1.75 seconds; and
Facility M is 2.1 seconds. In designing the test program in this
manner, the effect of secondary/tertiary chamber temperature and
residence time on the emissions of CDD/CDF, CO, and PM could be
evaluated. Figures 27, 28, and 29 present the data from these
112
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tests for CDD/CDF, CO, and PM, respectively, as a function of
both secondary/tertiary chamber temperature and residence time.
The data presented in these figures are the averages of the three
test runs conducted at each test condition. The data for each
facility are plotted in order of increasing residence time (x-
axis). The data for the 980°C (1800°F) test conditions conducted
at five of the six facilities are represented by solid triangles,
The data for the 870°C (1600°F) test conditions conducted at
three of the six facilities are represented by open squares-. For
each figure, to highlight the general trend of the results,
separate lines have been added to connect the 980°C (1800°F) data
points and the 870°C (1600°F) data points. Note that although CO
and CDD/CDF emissions were measured during the 870°C (1600°F)
general medical waste test condition at Facility A, PM emissions
were not measured. Therefore, the PM results from the 870°C
(1600°F) RB test condition are shown because, as discussed
earlier, there is little difference in the general medical and RB
emission rates. Also, note that the PM emissions are not shown
for Facility M. The results of the PM test at Facility M showed
that, as expected, a rotary kiln MWI has a higher post-combust ion
PM emission rate than other MWI's because of the increased
turbulence of the ash bed in rotary kilns. Therefore, the PM
data from Facility M were not comparable to the data from fixed
hearth MWI's. In reviewing the test data, the following general
observations can be made:
1. An increase in the secondary/tertiary chamber
temperature from 870°C (1600°F) to 980°C (1800°F) decreases the
emissions of PM, CO, and CDD/CDF for the tests conducted on units
with residence times of less than or equal to 1 second. As the
secondary chamber residence time increases, the effect on
emissions of increasing the secondary chamber temperature
decreases. Secondary chamber temperature has much less effect on
emissions for the facilities which had longer residence times and
better combustion air control. At Facility A (with a design
secondary chamber residence time of 1.34 seconds), there is
116
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essentially' no decrease in emissions as a result of increasing
the secondary chamber temperature;
2. As indicated by the downward trend in the lines
connecting the 870°C (1600°F) data and the 980°C (1800°F) data,
as the secondary/tertiary chamber residence time increases, the
emissions of CDD/CDF, CO and PM decrease;
3. The emissions measured at Facilities A, B, and M at a
nominal secondary/tertiary chamber temperature of 980°C (1800°F)
and a secondary/tertiary chamber residence time of at least 1.34
seconds are significantly lower than the emissions measured under
operating conditions with 870°C (1600°F) secondary chamber
temperatures and shorter residence times.
4.2.2.2.2. Primary chamber combustion control parameters.
In the primary chamber of most MWI's, waste is combusted under
substoichiometric air conditions. The purpose of maintaining a
substoichiometric air condition in the primary chamber is to
maintain control of the waste combustion rate. The objective is
to completely combust the waste in the primary chamber at a rate
that does not generate more combustible gases than the
secondary/tertiary combustion chambers can efficiently and
completely combust. The rate at which combustion proceeds in the
primary chamber can be controlled in several ways. These primary
chamber combustion control methods were described in Section 2
and include: (1) proper waste charging procedures; (2) control
of combustion airflow to the primary chamber; and (3) use of a
water spray. Proper waste charging procedures are operational
practices that include charging waste in charges of .similar
weight at regular intervals. The other two methods incorporate
MWI combustion control system designs that use primary chamber
temperature as an indicator of the rate of combustion in the
primary chamber. In these designs, when primary chamber
temperature exceeds a specified setpoint temperature, a control
loop is triggered that either decreases the combustion airflow
into the primary chamber or activates a water spray system to
help reduce temperatures below the setpoint.
117
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All MWI's control combustion in the primary chamber through
proper waste charging procedures. The combustion air rate and
distribution to the primary and secondary combustion chambers
also are controlled to some degree for all MWI's; however,
sophistication of the design of the air control system varies and
the level and degree of air control achieved varies widely. Some
MWI systems have combustion control designs that allow the
combustion air rate and distribution to be varied very little, if
at all, from predetermined settings during the combustion
process. As a result, these MWI's must rely solely on proper
charging procedures to maintain operation of the unit within the
limits of the preset conditions to achieve proper combustion.
Combustion control at Facility A is achieved through use of
a combination of techniques. First, the primary air combustion
rate is set at a level which will maintain the primary chamber at
a substoichiometric condition when the unit is charged at or near
the design rate. Second, a water spray system is provided in the
primary chamber to help quench the primary chamber combustion if
the temperature begins to exceed the desired level; the water
spray system is activated at a setpoint temperature of 730°C
(1350°F). Third, the waste charge amount and frequency is
carefully monitored and controlled. Secondary combustion air is
provided via a separate system which is independently controlled;
the secondary combustion air is fully modulated.
At Facilities K and W, a single combustion air blower
provides the air for the primary and secondary combustion
chambers. Combustion control is accomplished through the use of
a modulating damper that controls the distribution of the
combustion air to the primary and secondary chambers. The
control system at Facility W is fully modulated whereas at
Facility K, the modulating damper does not move very much about a
preset position.
One of the objectives of this test program was to determine
the impact on emissions of alternative waste charging practices,
At Facilities K and W, (MWI's with the same capacities but
different secondary chamber residence times), the following waste
118
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charging practices were employed: test condition 1 comprised
undercharging waste, i.e., charging at a rate (200 Ib/hr) less
than design capacity at 6-minute intervals; test condition 2
comprised charging waste at the MWI capacity charge rate
(300 Ib/hr) at 6-minute intervals; and test condition 3 was
comprised of charging waste at the MWI capacity charge rate
(300 Ib/hr) at 10-minute intervals (larger, less-frequent
charges) . '
Table 4 presents the average emission rates of PM, CO, and
CDD/CDF for the test conditions conducted at Facilities K and W.
It is clear that at Facility K, emissions of PM, CO, and CDD/CDF
increase from test condition 1 to test condition 2 to test
condition 3. The differences in emissions between test
conditions l and 2 are relatively small. The differences in
emissions between test conditions 2 and 3 are dramatic with a
four-fold increase in PM emissions, an order of magnitude
increase in CO emissions, and a five-fold increase in CDD/CDF
emissions. Note also, that the average primary chamber
temperature for test conditions 2 and 3 conducted at the design
capacity charge conditions (1820°F and 1835°F, respectively) also
were significantly higher than for test condition 1 (1620°F).
These data indicate that at Facility K,.infrequent waste charging
(large charges every 10 minutes as opposed to smaller charges
every 6 minutes) coupled with poor combustion control in the
primary chamber (as indicated by higher primary chamber
temperatures), and a lower secondary chamber temperature, results
in a significant increase in emissions.
The data obtained at Facility W also show an increase in
emissions of PM, CO, and CDD/CDF from test condition 1 to test
condition 2. The average primary chamber temperature for test
condition 2 was also higher than for test condition 1. However,
when the size and frequency of the charges were changed (larger.
less frequent charges--test condition 3) no increase in emissions
was noted. For test condition 3, the primary chamber temperature
was actually lower than for condition 2, indicating that
119
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Facility w"incorporates more effective primary chamber combustion
controls than Facility K.
At Facility A, the primary combustion chamber temperature
was controlled and maintained at a temperature of less than 730°C
(1350°F) for all runs, indicating good combustion control in the
primary chamber. Proper waste charging procedures were followed
for all test conditions. Charge rates.were adjusted based on the
target secondary/tertiary chamber temperature (i.e., lower charge
rates were used for the 870°C [1600°F] secondary chamber test
condition than for the 980°C [1800°F] test condition). The
emission results obtained during the test at Facility A indicate
that proper waste charging procedures coupled with good control
of primary chamber temperatures, a longer residence time (than
Facilities K and W), and good control of secondary/tertiary
chamber temperature produce the lowest emissions of PM, CO, and
CDD/CDF between Facilities A, W, and K.
423 Kmissiorg During Burndown and Cnnldown Phases
" Manual emission test data were collected at the seven
facilities during only the normal combustion component of the
operating cycle. However, CEM data were collected during the
burndown/cooldown phase at Facility A and during the cooldown
phase at Facility J. Figures 30 and 31 show example plots of CO
and THC concentrations for one 24-hour period at Facilities A and
j respectively. Corresponding plots of the'primary and
secondary chamber temperature profiles over the same 24-hour
periods are shown in Figures 32 and 33. The data from the other
test runs are comparable to those shown in the example plots.
These 24-hour CEM data indicate that at the two facilities
tested, CO and THC emissions during the cooldown period are
substantially higher than those during "normal" operations.
Also, given the very high levels of CO emissions measured (always
over'l 000 ppmv and sometimes as high as 50,000 pprrtv) and the
strong relationship between CO emissions and CDD/CDF found at
these high CO levels, CDD/CDF emissions during cooldown could be
substantial.
121
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WOOD-
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wghgOparaHo
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. Cooktown
12000 ^ -
i
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End Charging
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Begin Cooidown
Sec. Chamber
AuxBurneroB
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J™^;J.
09:30 11:00 1230 14:00 15:30 17:00 18:30 20:00 21.30 23:00 00:30 02:00 03:30 06:00 06:30
CO TU4E (24 HOUR) ^
Figure 30. 24-hour real time CO and
THC concentrations--Facility A, test condition 2, run number 2
60000 •>
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(Sundown)
soooo'
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Figure 31. 24-hour real time CO and
THC concentrations--Facility J, run numbers 5 and
122
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1900
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1700
1800
-Charging Operator
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SCTEMP
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400
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1 i
06:30 11:00 12:30
15.30 17:00 18:30 20:00 21.30 23:00 00:30 02:00 03.30 05:00 06,30
Figure 32. 24-hour temperature plot--Facility A,
test condition 2, run number 2.
2300 '•'
2200•'
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1700'
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sc TEMP
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(24 HOUR)
Figure 33. 24-hour temperature plot--Facility J,
run numbers 5 and 6.
123
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Further examination of the CEM data for the cooldown period
provides insight into potential control options. Figures 34 and
35 provide an expanded view of the cooldown period for the data
presented earlier. These figures overlay the CO concentration
curve and the temperature plots. Note that at both facilities,
primary chamber temperatures remain elevated for some period
after the cooldown period starts. (In fact, for some runs not
shown at Facility J, the primary chamber temperature actually
increased during cooldown). These elevated temperatures indicate
that waste burnout at these facilities has not been completed
before the start of the cooldown period. Consequently, unburned
organic material may still be released to the secondary chamber.
However, during the cooldown period the auxiliary fuel combustion
in the secondary chamber is substantially reduced or completely
shutdown, thereby accounting for the reductions in secondary
chamber temperature shown in the graphs. This secondary chamber
temperature decrease is accompanied by increases in CO
concentrations.
The available CEM data suggest that primary chamber
temperatures may be indicative of complete burndown, Generally,
CO concentrations appear to remain at high levels until primary
chamber temperatures fall to the 120° to 150°C (250° to 350°F)
range. These data suggest, therefore, that the significant
emissions during the cooldown period may be controlled by
maintaining the secondary chamber temperature at normal operating
levels until burndown is complete, as indicated by primary
chamber temperature.
4.2.4 Operating Cycle of a Batch MWI
Batch MWI's operate on a different cycle than intermittent
and continuous MWI's. In batch MWI's, all of the waste to be
burned during a complete batch cycle is loaded into the primary
chamber prior to operation with no additional waste charging
during operation. The batch operating cycle normally takes l to
2 days depending on the size of the MWI and the amount of waste
charged. In intermittent and continuous MWI's, waste is charged
124
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125
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in small charges on a regular basis throughout much of the
operating cycle.
In addition to the waste charging differences, the burn
cycle of a batch MWI proceeds differently than that of a
continuous or intermittent MWI. The burn cycle of a batch MWI
comprises three distinct phases--a low-air phase, a high-air
phase, and a cooldown phase. During the low-air phase,
combustion of the waste proceeds very slowly and primary chamber
temperature increases gradually over several hours. Combustion
proceeds more rapidly during the high-air phase and the primary
chamber reaches and maintains maximum operating temperatures.
Continuous and intermittent MWI's do not incorporate a low-air
phase and, therefore, reach maximum operating temperatures in
only a fraction of the time required for a batch unit.
Table 5 presents the average post-combustion emission
concentrations for test conditions conducted at the batch MWI at
Facility J during the low-air phase (test condition 1) and the
high-air phase (test condition 2). Additionally, Table 5
presents post-combustion emission concentrations for the test
conditions indicated for Facilities A, B, M, and W where the
target secondary/tertiary chamber temperatures were the same or
similar to the tests conducted at Facility J. In comparing the
emission concentrations for the low-air phase at Facility J with
the emission concentrations at the other facilities, the post-
combustion emission levels for all pollutants except Hg are
significantly lower for the batch MWI than for the intermittent
and continuous MWI's,, The emission concentrations for the high-
air phase at Facility J, however, are comparable to the
concentrations from the other facilities. These comparisons
suggest that during the high-air phase of operation, batch MWI's
achieve a somewhat steady-state operating level that is
equivalent to the steady-state levels of continuous and
intermittent units.
126
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127
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4.2.5 Metals Partitioning
In general, combustion control measures are not used to
limit metals emissions from MWI's. However, some combustion
parameters, particularly primary chamber temperature and
combustion air controls in the primary chamber, can affect the
partitioning of metals among the different incinerator exhaust
streams. The data from the EPA test program were examined to
determine whether the relative fractions of Cd, Pb, and Hg that
were partitioned to the bottom ash and exhaust gas varied
substantially across test runs, and if so, whether the
differences could be related to process operating conditions.
Data from the emission tests were sufficient to estimate
relative fractions of metals distributed to the bottom ash and
stack gas for a total of 15 test conditions at 4 "-.cilities.
Table 6 summarizes the average fraction of Pb, Cd, and Hg
partitioned to each of the two streams by facility and test
condition. Note that for Facility A, the ash samples collected
for each run were composited across the different runs by test
condition prior to metals analysis. Consequently, only one
sample was obtained per test condition and this one sample was
compared to average stack gas emissions over the runs that
constituted the test conditions. For other facilities, the
values in Table 6 are based on distinct ash and stack gas samples
for each of three runs per test condition.
With the exception of the data from Facility S, the
partitioning data are relatively consistent and follow expected
patterns. Generally, almost no Hg remains in the bottom ash,
with the percentage ranging from less than 1 percent at
Facilities A and W to about 6 percent at Facility K. Cadmium
partitions primarily to the stack gas with the percentage in the
bottom ash ranging from about 14 percent at Facility W to about
37 percent at Facility A. Finally, Pb partitions approximately
equally in the bottom ash and stack gas with the percentage in
the bottom ash ranging from 44 percent at Facility K to
59 percent at Facility A. Among these three facilities, the
128
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TABLE 6. SUMMARY OF BOTTOM ASH AND STACK GAS METALS
DISTRIBUTION
Facility
A
K
M
S
w
Test
condition
1
3
4 '
5
6
7
1
2
3
1
">
1
2 .
3
1
2
3
Cadmium
B-Ash
fraction,
mean
0.245
0.140
0.258
0.297
0.235
0.389
0.366
0.378
0.355
0.150
0.104
0.793
a
0.722
0.163
0.156
0.109
Stack
fraction,
mean
0.755
0.860
0.742
0.703
0.765
0.611
0.634
0.622
0.645
0.850
0.896
0.207
a
0.278
0.837
0.844
0.891
Lead
B-Ash
fraction,
mean
0.559
0.489
0.671
0.584
0.541
0.700
0.331
0.430
0.523
• 0.301
0.324
a
a
0.937
0.416
0.898
0.431
Stack
fraction.
mean
0.441
0.511
0.329
0.416
0.459
0.300
0.669
0.570
0.477
0.699
0.676
a
a
0.063
0.584
0.102
0.569
Mercurv
B-Ash
fraction.
mean
0.000
0.000
0.003
0.000
0.000
0.001
0.065
0.063
0.063
a
a
a
a
0.663
0.003
0.024
0.000
Stack
fraction.
mean
1.000
1.000
0.997
1.000
1.000
0.999
0.935
0.937
0.937
a
a
a
a
0.337
0.997
0.976
1.000
aAll B-ash values at detection limit. Fraction could not be determined.
B-ash: Bottom ash
Stack: Incinerator exhaust gas
distribution showed some variation, but the variation could not
be related to waste type or primary chamber temperature.
The distribution at Facility S differed substantially from
those at the other facilities with significantly greater
fractions of metals remaining in the bottom ash. The percentages
of metals in the bottom ash were Cd--75 percent and
Pb--90 percent. The results appeared to be consistent across
waste types. In general, primary chamber operating data appeared
to be reasonably consistent across facilities, and no explanation
was found for the difference between Facility S and the other
facilities. However, the data from Facility S should be
interpreted cautiously in that ash levels were near detection
limits.
129
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4.2.6 APCS' Performance
The emission test program generated performance data for
four APCS's--a DI/FF system at Facility A, a VS/PB system at
Facility B, a FF/PB system at Facility J, and a SD/FF system at
Facility M. At Facilities B and J, performance data were
collected for only a single test condition at each facility;
consequently parametric analyses of APCS performance at these
facilities were not feasible. However, data were collected for a
range of operating conditions at Facility A, making detailed
analysis of the DI/FF system performance possible.
The performance of these four APCS's is described in three
subsections below. The first briefly summarizes the performance
of VS/PB system and FF/PB system found at Facilities B and J,
respectively. The second presents the results of the evaluation
of the effect of system operating parameters on the DI/FF
performance at Facility A including the effect of activated
carbon injection. The third subsection describes the performance
of the SD/FF system at Facility M and the effect of activated
carbon injection on system performance.
4.2.6.1 Performance of the VS/PB and FF/PB Systems.
Pollutant specific removal efficiencies for PM, HC1, CDD/CDF, and
three metals (Cd, Pb, and Hg) are shown for each run at
Facilities B and J in Table 7. Note that for Facility J, the
test runs represent different components of the operating cycle.
Those test runs designated by BR are from the low-air component
of the cycle., while those designated as BD are from the high-air
component of the cycle.
The data from Facility B indicate that the VS/PB system
performs very well with respect to HC1 emissions with a
consistent removal efficiency of 99.8 percent or greater and
reasonably well with respect to CDD/CDF (approximately 70 percent
removal). Given the moderately high VS pressure drop (30 in.
water gauge), the PM removal efficiency was quite low, about
60 percent on the average. The particle size data collected at
the inlet to the VS/PB suggest that the particles at this
facility are relatively fine (about 60 percent of PM in the
130
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TABLE 7. PERFORMANCE OF THE VS/PB AND FF/PB AIR
POLLUTION CONTROL SYSTEMS
Facility
B
J
APCD
VS/PB
FF/PB
Test
MM 1-1
MM 1-3
MM 1-4
Jl-BR
J2-BD
J3-BR
J4-BD
J5-BR
J6-BD
Removal efficiency, percent
PM
48.3
21.2
72.4
>94.2
97.6
73.7
94.4
56.8
95.0
HC1
100
100
99.8
92.4
82.7
90.4
69.1
89.1
97.1
CDD/CDF
66.3
69.4
77.8
b
b
b
b
b
64.1
Cd
34.9
34.2
54.9
93.6
98.9
92.0
98.9
92.4
98.1
Pb
40.6
44.7
50.1
99.3
99.3
98.2
99.4
98.9
99.0
Hg
62.5
a
44.0
65.3
59.7
81.9
79.7
87.6
69.5
aOutlet Hg emissions measurements were higher than inlet Hg emissions measurements.
^Outlet emissions were higher than inlet emissions measurements by factors of 5 to 2.500.
submicron range), which may in part explain the low efficiencies.
Due in part to a low average inlet loading of 0.1 gr/dscf at
7 percent 02, Facility B did achieve moderately low outlet PM
concentrations with the outlet concentration averaging
0.046 gr/dscf at 7 percent 02. The VS/PB system provided some
removal of Cd (41 percent) and Pb (42 percent), but the
performance relative to Hg varied widely (no control up to
62.3 percent removal) suggesting that on the average, little Hg
control is achieved by the system.
The FF/PB at Facility J generally performed quite well with
respect to PM and metals emissions. The PM removal efficiencies
were generally 94 percent or higher with the exception of two
low-air component (74 and 57 percent) runs that had low inlet PM
loadings (0.004 gr/dscf for both runs). For all six runs, the
outlet PM loadings were less than 0.004 gr/dscf at 7 percent 02
.with an average outlet loading for the six runs of 0.0018 gr/dscf
at 7 percent 02- When metals inlet concentrations were at
"typical" levels such as those achieved during the high- air
component of the cycle, Cd removal efficiencies exceeded
98 percent while Pb removal efficiencies exceeded 99 percent.
For Hg, which showed no real variation between the two operating
cycle components, the overall removal efficiency was about
131
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73 percent with no apparent relationship between removal
efficiency and inlet loading. The HC1 removal efficiencies at
Facility J ranged from 69 to 97 percent with an average of
87 percent. The variation in efficiency had no apparent
relationship to inlet HC1 concentrations, and no apparent process
differences were found to account for the one extremely low
efficiency (69 percent on Test J4) or the generally poor
performance of the system. Subsequent to the test program, a
representative of the engineering firm that designed the facility
visited the facility to examine the APCS. He found that
approximately 2 months after the test, six of the eight scrubber
spray nozzles were plugged with material commonly encountered
during start-up.92 Although there had been a 2-month interval
since the test, the nature of the plugging material convinced the
engineering firm representative that it had probably been there
during the test and prevented adequate scrubbing liquor from
entering the scrubber and may have contributed to the low HC1
removal efficiencies.
For all but one test run at Facility J, the levels of
CDD/CDF were substantially higher at the APCD outlet than at the
heat exchanger inlet. An understanding of the system
configuration at Facility J helps in interpreting these results.
The exhaust from the incinerator first passes through an indirect
air-to-air heat exchanger into the fabric filter before passing
through the packed bed scrubber and out the stack. The post-
combustion sample location was upstream of the heat exchanger and
the post-APCS sample location was downstream from the packed bed.
The temperature drops from over 590°C (1100°F) at the inlet of
the heat exchanger to 85°C (185°F) at the outlet of the packed
bed scrubber. Although the exact amount of time required to
accomplish the drop in temperature is unknown, this range spans
temperatures over which de novo synthesis of ODD/CDF is.known to
occur. Consequently, CDD/CDF formation potentially occurred in
the heat exchanger, and/or fabric filter, and is not unexpected.
These data indicate that the CDD/CDF that is formed in the system
is not retained in the fabric filter or packed bed scrubber.
132
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4.2. 6." 2 Performanr-P of the DI/FF rontrol System. As
outlined in Section 4.1.1.1, two test sequences were performed on
the DI/FF system at Facility A. During 1990, tests were
conducted under 7 different operating conditions. Generally,
these different conditions were related to the incinerator
operation and were not.expected to affect the APCS performance.
However, lime rates were varied during those tests and factors
such as baghouse inlet temperatures and inlet gas moisture
content, which could affect the DI/FF performance, were monitored
during all tests. Subsequently, during 1991, additional tests
were conducted under three test conditions to assess the effects
of carbon injection on APCS performance. The paragraphs below
describe the performance of the DI/FF relative to PM, HC1,
CDD/CDF, and metals emissions and summarize the results of the
evaluation of the effects of operating parameters on performance.
The data on PM concentrations at the outlet of the DI/FF
system at Facility A that were presented in Table B-3 indicate
that the system typically achieves outlet PM levels corrected to
7 percent O2 of 0.004 gr/dscf or less. The four exceptions to
these low readings were test condition 1, run 1 (0.068 gr/dscf},
test condition 5, run 2 (0.056 gr/dscf), test condition 5, run 3
(0.088 gr/dscf), and test condition 7, run 1 (0.020 gr/dscf), all
of which were obtained during the first series of tests. Such
large variations in outlet concentrations are unusual for fabric
filter systems, and examination of plant operating data showed no
readily apparent differences in operating conditions during the
runs with high PM loadings. Also, the data showed no
deterioration in metals performance during those runs. Between
the 1990 and 1991 test series, all of the filter bags and the
entire outlet plenum were replaced. During the 1991 test series,
PM concentrations were consistently low with all runs measuring
0.004 gr/dscf or less @ 7 percent 02. The inconsistent results
obtained during the first test series indicate that the fabric
filter system might have been in need of repair at that time.
Consequently, the high PM levels found during a few runs at the
133
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first series of tests are not considered representative of FF
performance.
Two measures of HC1 performance were considered for
Facility A, mass emission rate-based removal efficiency and
concentration-based removal. Because the two measures were
highly correlated (r = 0.99) and concentration-based measures
were available for more test runs than were mass emission rate-
based measures, concentration-based efficiencies were used in the
analyses. Table 8 presents average removal efficiencies and
inlet and outlet concentrations for each of the nine test
conditions. The average removal efficiencies range from
93.2 percent for Condition 5 to 98.6 percent for Condition 8.
The average for Condition 5 was strongly influenced by a low
efficiency of 88 percent on one of the three runs. This
efficiency was substantially below the next lowest value of
92 percent.
TABLE 8. FACILITY A HC1 PERFORMANCE SUMMARY
Test condition
1
2
3
4
5
6
7
1A
8
9
l^^g^^gg^8fgB-J- - •_ Jl ,L MB
Inlet HC1 (ppmdv)
(@ 7% O7), mean
1,770
1,370
1,740
1,050
1,600
1,770
2,450
1,670
2,230
1,940
iBfea. Li^Lii... a. M m «... ••..! ..^ ,',„!..;., _ ^-™»
Outlet HC1 (ppmdv)
(©7% O2), mean
47.9
40.5
82.4
18.7
108
72.8
67.2
69.5
34.4
40.8
Efficiency concentration-
based, mean
97.5
97.1
95.3
98.3
93.2
95.4
97.0
96.0
98.6
97.9
The HC1 performance data were examined further graphically
and with a combination of correlation and regression analyses to
134
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assess the"affects of carbon injection, stoichiometric ratio, gas
temperature, and gas moisture on HC1 performance. No
relationship was found between performance and either gas
moisture or gas temperature. However, HC1 performance of this
system appears to be related strongly to stoichiometric ratio and
may be related to carbon injection, although the evidence related
to carbon injection is much weaker than that related to
stoichiometric ratio. These relationships are depicted
graphically in Figure 36, which shows a plot of HC1 removal
efficiency as a function of stoichiometric ratio with the carbon
injection runs circled. The HC1 efficiency has a strong
nonlinear relationship to stoichiometric ratio. For all runs
having a stoichiometric ratio of 6 or more, efficiencies of at
least 97 percent are achieved, while efficiencies for runs with
stoichiometric ratios of less than 6 range between 88 and
99 percent. Note that in the lower regime, the carbon runs
showed much higher efficiencies on average than did the noncarbon
runs. However, because performance did not appear to improve
with increased carbon usage, the effect of carbon usage on HC1
performance is considered to be inconclusive.
Metals emissions data were obtained for only seven of the
nine test conditions at Facility A. Table 9 summarizes the
removal efficiencies achieved by the DI/FF system for Cd, Pb, and
Hg for these seven conditions. The removal efficiencies for Cd
and Pb were 99 percent or greater irrespective of process
conditions. However, the Hg removal efficiencies were obviously
affected by carbon addition. During the six conditions that
involved no carbon injection (Nos. 1, 3, 5, 6, 7, and 1A),
essentially no Hg removal was achieved. At a carbon injection
rate of 0.45 kg/hr (1 Ib/hr) (Test Condition 8), the average
removal efficiency was 86 percent, and at a carbon injection rate
of 1.13 kg/hr (2.5 Ib/hr) (Test Condition 9), an average Hg
removal efficiency of about 95 percent was achieved. Taken
together, these data indicate that the DI/FF system can
consistently achieve Cd and Pb removal efficiencies of
135
-------
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136
-------
99 percent,"and with carbon injection, the system can achieve Hg
removal efficiencies in excess of 85 percent.
TABLE 9. SUMMARY OF METAL EFFICIENCIES BY TEST CONDITIONS
AT FACILITY A
Test condition
1
3
5
6
7
1A
8b
9°
Cd removal efficiency, %
99.5
99.5
98.8
99.4
99.1
99.6
99.6
98.8
Pb removal efficiency, %
99.5
99.3
99.7
99.6
99.4
99.7
99.7
99.5
Hg removal efficiency, %
9.0
42.7
a
10.7
a
a
86.3
94.7
aMeasured outlet Hg concentrations were higher than measured inlet Hg concentrations.
k Activated carbon at 1.0 Ib/hr.
cActivated carbon at 2.5 Ib/hr.
The run-specific CDD/CDF inlet and outlet concentrations for
Facility A are presented in Appendix B. Analysis of these data
suggest that in the absence of carbon injection, the DI/FF system
at Facility A achieves essentially no reduction in CDD/CDF. The
CDD/CDF mass flux data averaged across test conditions, which are
presented in Table 10, provide further insight into the
performance of the system relative to CDD/CDF emissions.
Table 10 contains average CDD/CDF mass flux rates by
conditions in units of /tg total CDD/CDF per hour for three
different DI/FF streams--the postcombustion gas stream to the DI
unit, the stack gas stream exhausted from the FF (post-APCS), and
the FF catch discharge. Table 10 also presents the ratio of
CDD/CDF stack gas mass flux to the postcombustion CDD/CDF mass
flux and the ratio of the total APCS CDD/CDF discharge rate
(stack gas plus FF catch) to postcombustion CDD/CDF mass flux.
For the test conditions involving no carbon injection
(Conditions 1, 2, 3, 6, 7, and 1A), the post-APCS to
postcombustion ratio ranges from 0.47 to 1.24 with an average of
137
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TABLE 10. SUMMARY OF CDD/CDF PERFORMANCE DATA FOR THE DI/FF
AT FACILITY A
CDD/CDF mass flux, /xg/hr
Test
condition
lb
2
3
6
7
1AC
8c,d
9c,e
Post-
combustion
759
615
623
745
786
325
591
576
Post-
APCS
943
514
520
353
884
201
23.8
10.2
FF
catch
285
467
892
625
502
245
540
1,140
Post-APCS to
postcombus-
tion ratio
1.24
0.84
0.83
0.47
1.12
0.62
0.040
0.018
Total APCS
discharge to
postcombus-
tion ratioa
1.62
1.60
2.27
1.31
1.76
1.37
0.95
2.00
of the CDD/CDF measured in the post-APCS and FF catch streams.
"Data from 1990 test series.
jData from 1991 test series.
QActivated carbon at 1.0 Ib/hr.
Activated carbon at 2.5 Ib/hr.
0.85. These ratios are consistent with essentially zero CDD/CDF
control in the absence of carbon injection. However, when carbon
was injected at a rate of 1 Ib/hr, the ratio fell to 0.04 which
is equivalent to a 96 percent reduction in CDD/CDF emissions.
When the carbon injection rate was increased to 2.5 Ib/hr, the
ratio fell to 0.018, which represents a 98.2 percent CDD/CDF
removal efficiency. On balance, these data suggest that a DI/FF
system with carbon injection can achieve average CDD/CDF removal
efficiencies of 95 percent or greater.
While the data in Table 10 indicate that DI/FF systems with
carbon injection can reduce stack emissions of CDD/CDF, they also
indicate that CDD/CDF formation occurs within the DI/FF system.
With the exception of the 1 Ib/hr carbon injection conditions,
which comprised only two runs with variable results, the ratio of
total CDD/CDF discharged to postcombustion CDD/CDF range from 1.3
to 2.3. These ratios suggest that at this facility with
138
-------
incinerator'APCS inlet levels in the range of 300 to 500 ng/dscm
at 7 percent 02 the amount of CDD/CDF formed in the system can be
50 to 100 percent of that entering with the combustion gas. To
date, no relationship between this formation rate and DI/FF
operating conditions has been found.
4.2.6.3 Performance of the SD/FF Control System. The SD/FF
system at Facility M was tested under two sets of operating
conditions. During Condition 1, normal facility operating
conditions for both the incinerator and APCS were used. The same
operating levels were used during Condition 2, except that
activated carbon was added to the lime slurry to produce a carbon
rate of about l.l kg/hr (2.5 Ib/hr). In general, most process
parameters were maintained at nearly constant levels for all runs
except stoichiometric ratio. Because the lime feed rate was
nearly constant, the stoichiometric ratio fluctuated somewhat
with inlet HC1 loadings. The only major operating difference
occurred during Run 1. For that run the lime concentration in-
the slurry was maintained at 6 percent by weight in contrast to
9 percent by weight for the other five tests. Consequently, the
lime feed rate and stoichiometric ratio were lower for Run 1 than
for the other five runs. Because all other parameters varied so
little, the only factor that was examined in detail was the
effect of carbon addition. The paragraphs below provide a
general discussion of the performance of the system with respect
to PM, HC1, CDD/CDF, and metals and discuss the effect of carbon
addition on CDD/CDF and metals performance.
The SD/FF system yielded outlet PM concentrations that
ranged from 0.0006 to 0.0098 gr/dscf at 7 percent 02, and with
the exception of Run 2, all concentrations were below
0.002 gr/dscf at 7 percent 02- Average outlet PM concentrations
were 0.0038 for Condition 1 and 0.0011 for Condition 2, and
carbon appeared to have no effect on emissions.
Because analytical data were outside allowable quality
control limits for two runs, HC1 performance data are available
for only four test runs. These data are shown in Table 11.
Although the data are somewhat limited, they do indicate that
139
-------
stoichiometric ratio is important to the system's performance.
Additionally, the data indicate that if a stoichiometric ratio of
two or greater is maintained, HC1 control efficiencies of at
least 99 percent were achieved by the system.
TABLE 11. HC1 PERFORMANCE DATA FOR FACILITY Ma
Run No.
3
4
5
6
Lime rate,
Ib/hr
37
34
31
32
SR
3.39
1.91
2.29
2.11
Activated
carbon
rate,
Ib/hr
0
2.8
2.5
2.5
HC1 concentration,
ppmdv at 7V O?
Inlet
724
1,220
946
1,030
Outlet
4.50
26.1
<0.049
<0.045
Removal
efficiency
99.3
97.8
>99.99
>99.99
aHCl analytical data for run number 1 and 2 were outside control limits
and are not reported.
The SD/FF performance data for metals and CDD/CDF are
summarized in Table 12. These data indicate that for Cd and Pb,
the SD/FF is highly efficient (99.7 percent or greater) under
both test conditions. These findings were consistent across test
runs within each condition. However, for both Hg and CDD/CDF,
the system yielded substantially greater reduction with activated
carbon addition than without. For Hg, the average removal
efficiency without activated carbon was about 30 percent with the
efficiencies on individual runs ranging from no control to
50 percent. When activated carbon was added not only was the
average removal efficiency higher (90 percent), but system
performance also was more consistent with efficiencies for
individual runs ranging from 84 to 96 percent. These data show
that an overall Hg removal efficiency achieved by a SD/FF system
with activated carbon injection is similar to that achieved by a
DI/FF system with activated carbon injection.
With no activated carbon added to the system, the average
CDD/CDF removal efficiency was 84 percent with a range of 56 to
95 percent. As was the case with Hg, addition of activated
carbon both increased average efficiency and provided more
consistent performance. The average removal efficiency was about
140
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TABLE 12. SUMMARY OF CDD/CDF AND METALS PERFORMANCE
FOR SD/FF SYSTEM5
Pollutant
Cd
Pb
Hg
CDD/CDF
CDD/CDF
(balance)
Parameter
postcombustion, jtg/dscm
post-APCS, /ig/dscm
Removal efficiency. %
postcombustion, /ig/dscm
post-APCS, /tg/dscm
Removal efficiency, %
postcombustion, jtg/dscm
post-APCS, /ig/dscm
Removal efficiency, %
postcombustion, jig/dscm
post-APCS, /tg/dscm
Removal efficiency, %
postcombustion, ftg/hr
post-APCS, /ig/hr
SD catch, ;tg/hr
FF catch, fig/hr
post-APCS: postcombustion ratio
Total out:Total in ratio
Condition 1
(no carbon)
471
1.77
99.7
3,590
5.7
99.9
2,590
1,980
29.6
192
32.2
94.0
820
131
12.8
589
0.16
0.89
Condition 2
(with carbon)
492
0.84
•99.8
4,410
2.5
99.9
2,630
284
90.0
199
3.30
98.3
848
14.5
5.27
484
0.017
0.59
98 percent with individual runs having efficiencies in the range
of 95 to 99 percent. Two additional observations concerning the
CDD/CDF data in Table 12 are worth noting. First, even without
activated carbon addition a substantial reduction in CDD/CDF
emissions was achieved by the system, a dramatic contrast to the
absence of control found with the DI/FF system. Second, unlike
the results obtained for the DI/FF system, the mass balance
around the control system shows no evidence of CDD/CDF formation
across the system. Although no definitive explanation was found
for why CDD/CDF formation occurred in the DI/FF system but not in
the SD/FF system, the system characteristics that may have the
greatest effect are the quick cooling/adsorption obtained with
the slurry spray in the SD/FF, the longer gas/lime residence time
prior to the FF provided by the SD vessel, and the lower FF
temperatures of the SD/FF system (146°C [295°F]) compared to the
DI/FF system (163°C [325°F]). In addition, it should be noted
141
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that the MWI preceding the SD/FF system is a rotary kiln design
with significantly higher post-combustion levels of PM. This
increased level of PM would indicate that significantly more
carbon existed in the gas stream entering the SD/FF than in the
gas stream entering the DI/FF, which may have aided the
performance of the SD/FF. The results from these tests indicate
that an overall CDD/CDF removal efficiency of at least 98 percent
can be achieved by this SD/FF system with activated carbon
injection.
4.3 DEMONSTRATED EMISSION CONTROL LEVELS
The purpose of this section is to present demonstrated
emission control levels (i.e., emission limits) associated with
each of the emission control techniques discussed earlier. Each
of nine pollutants is presented in a separate subsection. Each
subsection includes tables showing the emission limits and
figures presenting the data used to establish these limits.
The emission limits were developed from actual test data
from EPA-sponsored emission tests conducted at seven MWl's.
Table 13 presents a summary of information on the type and size
of each MWI tested. Other data were also considered (e.g.,
emission test reports submitted to State agencies), but none of
these data were used in establishing emission limits because the
test reports were incomplete (i.e., lacked process or design
information and/or lacked information on sampling techniques).
In establishing the emission limits for all pollutants, the
amount of data available and variation in that data were taken
into consideration. Except for HC1 controlled by DI/FF systems,
the emission limits were set above the highest 3-run average
shown by the data. For HC1 controlled by DI/FF systems, the
emission limit is set above the highest individual runs with SR's
above 6:1. For pollutants and/or MWI types where limited test
data are available, appropriate data from related pollutants
and/or MWI types were considered.
The numerical emission limit only has meaning when coupled
with an averaging time. During each of the tests conducted at
the seven MWI facilities, emissions were measured over three
142
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TABLE 13. TESTED MWI FACILITIES
Facility
A
B
J
K
M
S
w
Description
650 Ib/hr, intermittent, ram-fed; 2-sec
secondary chamber; DI/FF system tested
activated carbon injection
1,500 Ib/hr, continuous, ram-fed; 2-sec
secondary chamber; VS/PB system
750 Ib/batch, batch, manually fed; 1.75
in secondary chamber; FF/PB system
300 Ib/hr, intermittent, manually fed;
time in secondary chamber
residence time in
with and without
residence time in
-sec residence time
0.33 -sec residence
800 Ib/hr, continuous, ram-fed; 2-sec residence time in
secondary chamber; SD/FF system tested with and without
activated carbon injection
250 Ib/hr, intermittent, manually fed; 0. 2-sec residence
time in secondary chamber; conditions 1 and 2 =
pathological waste, condition 3 = mixed medical waste
300 Ib/hr, intermittent, ' ram- fed; 1-sec residence time in
secondary chamber
4-hour periods. Therefore, the emission limits are based on a
12-hour average consisting of three 4-hour test runs.
Continuous, intermittent, batch, and pathological MWI's are
four different MWI types (based on their physical design
characteristics, operating characteristics, and overall emission
profiles). However, for continuous, intermittent, and batch
units, there is a period in the combustion cycle when the
emission profiles are similar. In continuous and intermittent
units, this period occurs- during waste-charging. In a batch
unit, this period occurs in what is sometimes referred to as the
"high-air" or "burndown" phase. In all three MWI types, this
period can be distinguished by the temperature in the primary
chamber. This is also the period of highest emissions.
Consequently, data taken during this period from these three MWI
types have been combined in establishing one set of emission
limits for continuous, intermittent, and batch MWI's. There is
no corresponding period in a pathological unit during which
emissions are comparable to the other types of units. Therefore,
data from only pathological units have been used to set emission
limits for pathological MWI's.
143
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The nine pollutants discussed in this section fall into two
categories: those dependent upon the composition of the waste
being burned and those dependent upon the MWI combustion process.
Waste-related pollutants (HC1, S02, Cd, Pb, and Hg) are formed as
a result of the presence of components within the waste and are
unaffected by combustion controls. Combustion-related pollutants
(PM, CO, and CDD/CDF) are emitted at different levels from
different MWI's depending on the waste-charging patterns, the
temperature maintained in the secondary chamber, and the gas
residence time in the secondary chamber. Nitrogen oxides can be
considered both waste-related and combustion-related. However,
neither the combustion controls nor the add-on controls evaluated
in this analysis achieved any NQX reduction (see Section 4.3.9).
Because combustion conditions do not affect waste-related
pollutants, applying only combustion control options result in
uncontrolled emission levels of these pollutants. As a result,
combustion control limits have not been established for these
pollutants.
Establishing emission limits for the combustion-related
pollutants was difficult because not all possible combinations of
combustion control and MWI type were tested. Of the four MWI
types, only intermittent units were tested at each of the three
combustion control levels (see Table 14).
TABLE 14. COMBUSTION CONTROL DATA vs. MWI TYPES
Continuous
Intermittent
Batch
Pathologies]
Uncontrolled
K, S (condition 3)
S (conditions 1 and 2)
1-sec
W
2-sec
B, M
A
J
For continuous, intermittent, and batch MWI's, data from
facility K (conditions 1 and 2) and facility S (condition 3)
represent uncontrolled emission levels; data from facility W
(conditions 1 and 2) were used to establish the emission limits
144
-------
for l-sec combustion; and data from facilities A, B, J
(condition 2), and M were used to establish the emission limits
for 2-sec combustion. Data from test condition 3 at facilities K
and W were not considered in establishing emission limits based
on combustion control because both MWI's were purposely
overcharged during these test conditions to show the effects of
poor MWI operation.
For pathological MWI's, only one level of combustion control
was tested (uncontrolled at facility S) . To establish emission
limits for pathological MWI's at each combustion control level,
the relationships of the emission limits established for the
other types of MWI's were applied to the data for the
pathological MWI's to calculate emission limits for the untested
conditions.
'control options reflecting add-on controls combine 2-sec
combustion with an add-on control device. Emission limits for
these control options were established based on inlet/outlet
tests conducted on MWI's with add-on control. Typically, the
emission reduction capability is expressed as a percent reduction
relative to the 2-sec combustion emission limit. Exceptions to
this approach are PM, Pd, and Cd emissions from fabric filter
systems, which are capable of achieving constant outlet levels
for these pollutants. For pollutants that are unaffected by
combustion controls (waste -related pollutants for all MWI's and
PM for pathological MWI's) the 2-sec combustion emission limit is
equivalent to the uncontrolled emission level (the highest 3-run
average of uncontrolled emission data) .
The remainder of this section is divided into nine
subsections, one for each pollutant. These subsections present
the emission limits for each MWI type and show the data used to
determine the emission limits.
4.3.1 Pfrrtieulate Matter
Table 15 presents the PM emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 37 through 39 present the data used to develop
145
-------
these emission limits. At the facilities tested, the PM
emissions were reported in gr/dscf. However, to be consistent
with emission limits for other pollutants, the PM emission limits
in this section are expressed in metric units (milligrams per dry
standard cubic meter [mg/dscm]).
TABLE 15. PM EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI'S
Control option
1-scc
2-sec
Wet systemsb
FF/PBb
DI/FFb
SD/FFb
Fabric filter systems with carbon
injection13
PM emission limits,
mg/dscm at 7 percent 02
Continuous, intermittent, batch
600
• 300
150
30
30
30
30
Pathological
NAa
• NAa
58
30
30
30
30
aNo applicable limit. Highest 3-run average of uncontrolled
data =115 mg/dscm (facility S condition 2).
2-sec combustion.
4.3.1.1 Combustion Controls--PM. Figure 37 presents PM
emission data for continuous, intermittent, and batch MWI's
burning general medical waste. Data from facilities K and S
reflect uncontrolled PM emission levels. The PM emission limit
for 1-sec combustion is based on facility W, and was set
relatively close to the majority of individual test runs because
1-sec combustion will exhibit less variation in PM emissions than
uncontrolled levels. Test data show that at higher residence
time, combustion-related emissions are less affected by the MWI
operation. The PM emission limit for 2-sec combustion is based
on facilities A, B, and J. In this case, the emission limit has
been set very close to the highest 3-run average and very close
to most of the individual test runs because the large amount of
146
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2200-
2100 -;
2000:
1900:
1800:
1700:
1600:
1500:
1400^
S 1300:
1100 -i
900:
800:
700:
600:
500:
400^ *
300 :~
200^*
100 ^
0-
*
K K S
1 2 3
Uncontrolled
Figure 37.
W W
1 2
1-sec comb.
AAAAAAAAABJJ
134567189112
a
2-sec combustion
PM emissions for continuous, intermittent, and batch
MWI's with combustion controls.
147
-------
data available for these units indicate that this limit can
consistently be achieved. Facility M was not considered in
developing the PM limit for 2-sec combustion because the unit at
this facility is a rotary kiln MWI that, as expected, had higher
PM emissions due to the turbulence of the waste in the primary
chamber. This turbulence results in entrainment of non-
combustible ash, which will not be affected by combustion
control.
Figure 38 presents PM emission data for pathological MWI's
(facility S, uncontrolled) . Compared to PM emissions from an MWI
firing general medical waste, PM emissions from a pathological
MWI will be lower, more stable, and less affected by combustion
control. Pathological MWI's operate with excess air in the
primary chamber, which limits the generation of incomplete
combustion products but increases the entrainment of ash. The
result is a higher fraction of non-combustible material (not
affected by combustion control) in the PM emissions. Emissions
of PM from pathological MWI's will be very stable because of the
homogeneous nature of pathological waste and the absence of
incomplete combustion products. Because combustion controls do
not reduce PM emissions from pathological MWI's, no limits were
established for the 1-sec and 2-sec control options.
4.3.1.2 Add-On Controls--PM. Figure 39 presents PM removal
efficiencies and outlet levels achieved with the add-on control
technologies tested. The PM outlet concentrations achievable
with wet systems depend on the inlet loadings and therefore are
based on a percent reduction rather than a constant outlet value.
Facility B data indicate that wet systems are capable of
achieving a PM removal efficiency of at least 50 percent. This
performance is applicable to all MWI types.
The remaining control technologies use a fabric filter to
control PM emissions. The emission limit for these technologies
is based on a constant outlet value achievable with a fabric
filter as demonstrated at facilities A, J, and M. Test
conditions l through 7 at facility A were not considered in
establishing the PM emission limit for fabric filter systems.
148
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23M-"
2100-
2000-
1900-
1700-
1500-
1400-
1300-
1200-
JIOOO
I 900
700-
500-
400^
300
200-
100^
4
SI 82
lU.ii.Jptiliirl
unconBonu
Figure 38. PM emissions for uncontrolled pathological MWI's,
149
-------
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I-
2100-
2000
1900-
1700-
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S*
r
1500
1400
1900
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500
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Jl
J2
Ml
M2
Figure 39.
ftWcFtor Systems
PM emissions for continuous, intermittent, batch, and
pathological MWI's with add-on controls.
150
-------
Outlet PM concentrations varied significantly for these tests,
which were obtained during the first series of tests at
facility A. Prior to the second series of tests, the fabric
filter bags were replaced. The consistently low outlet PM levels
achieved during this second series of tests, along with data from
facilities J and M, indicate that the fabric filter was not
functioning properly during the first series of tests at
facility A, which invalidates PM runs 1 through 7 at facility A.
Based on facility A (conditions 1A, 8, and 9), and on facilities
J and M, PM concentrations of 30 mg/dscm are achievable by fabric
filter systems.
4.3.2 Carbon Monoxide
Table 16 presents the CO emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 40 and 41 present the data used to develop these
emission limits.
TABLE 16. CO EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI'S
Control option
1-sec
2-sec
Wet systems3
FF/PBa
DI/FF8
SD/FFa
Fabric filter systems with carbon
injection*
CO emission limits, ppmdv at 7 percent O2
Continuous, intermittent, batch
500
50
50
50
50
50
50
Pathological
50
10
10
10
10
10
10
alncludes 2-sec combustion.
4.3.2.1 Combuation Cnntrols--CO. Figure 40 presents CO
emission data for continuous, intermittent, and batch MWI's
burning general medical waste. Data from facilities K and S
reflect uncontrolled CO emission levels. The CO emission limit
151
-------
2800-~
2600-
2400-
2200-
2000-
1800-
0 1600-
1400-
1200-
1000-
800-
•5*
a
8
600-
400-
4
i
200^
T
1
*
*******
* *
K K S
1 2 3
Uncontrolled
Figure 40.
W W
1 2
AAAAAAAAAABJ JMM
123456718911212
a
2-sec combustion
CO emissions for continuous, intermittent, and batch
MWI's iwth combustion controls.
152
-------
for l-sec combustion is based on facility W, and was set
relatively close to the majority of individual test runs, because
l-sec combustion will exhibit less variation in CO emissions than
uncontrolled levels (as previously discussed for PM emissions).
The CO emission limit for 2-sec combustion is based on
facilities A, B, J, and M. In this case, the emission limit has
been set very close to the highest 3-run average and very close
to each of the individual test runs because the large amount of
data available for these units indicate that this limit can-
consistently be achieved.
Figure 41 presents CO emission data for pathological MWI's
(facility S, uncontrolled). Compared to CO emissions from an MWI
firing general medical waste, CO emissions from a pathological
MWI will be lower and more stable, but improved combustion
control will further reduce CO emissions. Pathological MWI's
operate with excess air in the primary chamber, which limits the
generation of incomplete combustion products. However,
combustion control will further reduce these emissions.
Emissions of CO from pathological MWI's will be very stable
because of the homogeneous nature of pathological waste. The CO
limit for l-sec combustion control is calculated using the ratio
of the l-sec CO limit to the uncontrolled CO emission level for
general-waste units (500/1,200) and applying this ratio to the
uncontrolled CO emission level for pathological MWI's (130).
Uncontrolled emission levels are represented by the highest 3-run
averages of the uncontrolled emissions data (facility S
condition 3 for continuous, intermittent, and batch MWI's and
facility S condition 2 for pathological MWI's). The CO limit for
2-sec combustion control is calculated using the ratio of the
2-sec CO limit to the uncontrolled CO emission level for general-
waste units (50/1,200) and applying this ratio to the
uncontrolled CO level for pathological MWI's (130).
4.3.2.2 Add-On Controls--CO. Add-on control devices are
not effective in further removing CO emissions. As a result, the
limits for all add-on control techniques are the same as those of
2-sec combustion control.
153
-------
2400
2200
2000
1800 -;
1600-
81000
4-
SI S2
Uncortrokd
Figure 41. CO emissions for uncontrolled pathological MWI's,
154
-------
4.3.3 ninx'ins and Furans
Table 17 presents the CDD/CDF emission limits under each
control option for continuous, intermittent, batch, and
pathological MWI's. Figures 42 through 44 present the data used
to develop these emission limits.
TABLE 17. CDD/CDF EMISSION LIMITS FOR CONTINUOUS,
TNTERMITTENT, BATCH, AND PATHOLOGICAL MWI'S
CDD/CDF emission limits, ng/dscm at 7 percent
Continuous, intermittent, batch
Fabric filter systems with carbon
alncludes 2-sec combustion.
bLamits reflect CDD/CDF generation across FF/PB system.
cThe CDD/CDF emission limits achievable with a FF/PB system
with activated carbon injection are not known.
4.3.3.1 rnmhnstion rv^i-rols- -CDD/CDF. Figure 42 presents
CDD/CDF emission data for continuous, intermittent, and batch
MWI's burning general medical waste. Data from facilities K and
S reflect uncontrolled PM emission levels. The CDD/CDF emission
limit for l-sec combustion is based on facility W, and was set
relatively close to the majority of the individual test runs
because l-sec combustion will exhibit less variation in CDD/CDF
emissions at uncontrolled levels (as discussed earlier for PM and
CO). The CDD/CDF emission limit for 2-sec. combustion is based on
facilities A, R, J, and M. In this case, the emission limit has
been set very close to the highest 3-run average and very close
to each of the individual test runs because the large amount of
155
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40000-
35000-
30000-
S- 25000-
&
I
o
20000-
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_*
5000-7
0-
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K K S
1 2 3
Uncontrolled
W W
1 2
1-see comb.
AAAAAAAAABJJMM
12346718911212
a
2-sec combustion
Figure 42.
CDD/CDF emissions for continuous, intermittent, and
batch MWI's with combustion controls.
156
-------
data available for these units indicate that this limit can
consistently be achieved.
Figure 43 presents CDD/CDF emission data for pathological
MWi's (facility S, uncontrolled). Compared to CDD/CDF emissions
from an MWI firing geneal medical waste, CDD/CDF emissions from a
pathological MWI will be lower and more stable, but improved
combustion control will reduce CDD/CDF emissions. Pathological
MWI's operate with excess air in the primary chamber, which
limits the generation of incomplete combustion products. .
However, CDD/CDF emissions can be further reduced by combustion
control. Emissions of CDD/CDF from pathological MWI's will be
very stable because of the homogeneous nature of pathological
waste The CDD/CDF limit for 1-sec combustion control is
calculated using the ratio of the 1-sec CDD/CDF limit to the
uncontrolled CDD/CDF emission level for general-waste units
(7,000/25,000) and applying this ratio to the uncontrolled
CDD/CDF emission level for pathological MWI's (910).
Uncontrolled emission levels are represented by the highest 3-run
averages of the uncontrolled emissions data (facility S condition
3 for continuous, intermittent, and batch MWI's and facility S
condition 1 for pathological MWI's). The CDD/CDF limit for 2-sec
combustion control is calculated using the ratio of the 2-sec
CDD/CDF limit to the uncontrolled CDD/CDF emission.level for
general-waste units (1,500/25,000) and applying this ratio to the
uncontrolled CDD/CDF emissions for pathological MWI's (910).
4.3.3.2 Arid-on Consols- -CDD/CDF. Figure 44 presents the .
CDD/CDF removal efficiencies and outlet concentrations of the
add-on control technologies tested. The CDD/CDF emission limit
for the wet systems is based on the 70-percent removal efficiency
demonstrated at facility B. The three fabric filter systems
without activated carbon injection achieved varying levels of
CDD/CDF control. In fact, formation of CDD/CDF occurred in one
system.
Formation of CDD/CDF occurs when there is intimate contact
between a gas stream containing CDD/CDF precursors and fly ash,
which acts as a catalyst. The optimum temperature window for fly
157
-------
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40000
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30000
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Figure 43.
CDD/CDF emissions for uncontrolled pathological
MWI's.
158
-------
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Fiqure 44 CDD/CDF emissions for continuous, intermittent,
batch, and pathological MWI's with add-on controls.
159
-------
ash catalyzed CDD/CDF formation is between 300°F and 600°F. The
CDD/CDF formation is minimized when using combustion control or
wet systems because these options provide: (1) rapid cooling of
the gas stream through the temperature window and (2) quick
dispersion (or removal in the case of wet systems) of CDD/CDF
precursors and fly ash. In DI/FF and SD/FF systems, the presence
of an acid gas sorbent (lime, for example) also limits the
formation of CDD/CDF. • The fabric filter in a FF/PB- system, on
the other hand, can provide those conditions conducive to CDD/CDF
formation. In fact, test data have shown CDD/CDF formation in a
FF/PB system.
The emission limit for the FF/PB system is based on test
data from facility J, which shows a generation of CDD/CDF across
the system. Figure 44 shows the outlet CDD/CDF emissions at
facility J. Because facility J burns general medical waste, the
actual test data could not be used directly in establishing an
emission limit for pathological MWI's. As a result, the limit
for the pathological MWI has been calculated based on the CDD/CDF
generation rate at facility J. The generation rate is based on
the FF/PB outlet limit (7,000 nanograms [ng]/dry standard cubic
meter [dscm]) and the 2-sec combustion limit (1,500 ng/dscm) at
facility J. This generation rate was applied to the 2-sec
combustion limit for pathological MWI's to determine the FF/PB
limit for this MWI.
The CDD/CDF emission limit for the DI/FF system is based on
test data from facility A. This test data showed no consistent
CDD/CDF removal from the DI/FF system without carbon injection.
Therefore, the limit for this technology is the same as that of
2-sec combustion control.
Test data from facility M indicate that a SD/FF system on a
rotary kiln MWI is capable of achieving 80-percent CDD/CDF
reduction. However, this significant reduction may be due to the
rotary kiln design (the higher PM emissions may aid in the
removal of CDD/CDF). It is not known if a SD/FF system (without
activated carbon injection) can achieve this same level of
control on the other MWI designs. On the other hand, a SD/FF
160
-------
system is not expected to generate CDD/CDF for the reasons
described above. Therefore, the limit for this technology is the
same as that of 2-sec combustion control.
Test data from facilities A and M indicate that the DI/FF
and SD/FF systems with activated carbon injection are effective
in significantly reducing CDD/CDF emissions (see Figure 44).
These two fabric filter systems (with activated carbon injection)
are able to achieve at least 95-percent CDD/CDF control. Because
data are not available from a FF/PB system with activated carbon
injection, and because the FF/PB system tested without carbon
injection generated CDD/CDF, it is not known what CDD/CDF
reductions are achievable with the activated carbon in a FF/PB
system.
4.3.4 Hydrogen Chloride
Table 18 presents the HC1 emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 45 through 47 present the data used to establish
these emission limits.
4.3.4.1 combustion Controls--HC1. Figure 45 presents HC1
emission data for continuous, intermittent, and batch MWI's
burning general medical waste, and Figure 46 presents these data
for pathological MWI's. Because emissions of HC1 are waste-
related, combustion controls do not reduce HC1 emissions.
4.3.4.2 Add-on Controls--HC1. Figure 47 presents the HC1
removal efficiencies of the add-on control technologies tested.
The emission limit for wet systems is based on test data from
facility B, while the emission limit for fabric filter systems is
based on data for a DI/FF system from facility A and a SD/FF
system from facility M. The data show that each of these systems
can reduce HC1 emissions by at least 97 percent. This
corresponds to an emission level of 42 ppmdv for a typical
continuous, intermittent, or batch unit (97 percent reduction
from a typical uncontrolled level of 1,400 ppmdv); and 4 ppmdv
for pathological units (97 percent reduction from a typical
uncontrolled level of 120 ppmdv).
161
-------
TABLE 18. HC1 EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI' S
Control option
1-sec
2-sec
Wet systems**
FF/PBb
DI/FFb
SD/FFb
Fabric filter systems with carbon
injection*5
HC1 emission limits, ppmdv at 7 percent O2
Continuous, intermittent, batch
NAa
NAa
42C
42C
42C
42C
42C '
Pathological
NAa
NAa
4C
4C
4C
4C
4C
*No applicable limit.
^Includes 2-sec combustion.
cThese emission limits correspond to a reduction of 97 percent.
For the DI/FF system without a retention chamber, as at
facility A, greater than 97 percent reduction is achieved when
the stoichiometric ratio is at least 6:1. (In some cases,
similar reductions can also be achieved with lower stoichiometric
ratios). The 3-run test averages at facility A were not used in
establishing the HC1 emission limit because, as shown on
Figure 47, the stoichiometric ratio was below 6:1 for at least
1 run at each of the test conditions, except test condition 4.
Test data for a DI/FF with a retention chamber are unavailable.
However, as noted earlier in this report, vendors indicate that a
50 percent lower stoichiometric ratio can be used in a system
with a retention qhamber to achieve the same reduction as a
system without a retention chamber.
For the SD/FF system at facility M, test runs were conducted
with stoichiometric ratios between 1.9 and 3.4, and the resulting
emission reductions were greater than 98 percent for each run.
162
-------
2800 -~
2600-
2400-
2200-
2000-
1800-
1600-
*
*
1400-
r 1200-
o
1000-1
800-
600
400
*
*
* *
200-
0-
K K K S
1233
Uncontrolled
*
¥
WWW
1 2 3
1-sec comb.
AAAAAAAAABJ JMM
12345618911212
a
2-sec combustion
Figure 45. HC1 emissions for continuous, intermittent, and batcn
MWI's with combustion controls.
163
-------
2400-
2200
2000
1600-
1400-
S.
1200
iooo
400
T
0-
SI
S2
Figure 46. HC1 emissions for uncontrolled pathological MWI's,
164
-------
100
90-
t-s
-o-
0
tx 8
o
8
80-
70-
§ 60
50
• Data used to establish emission limit:
- - DI/FF runs with SR >6
All wet system runs
- - All SD/FF runs
O Data not used to establish emission limits;
DI/FF runs with SR <6
40-
30-
20-
10-
0-
B1
A1 A2 A3 A4 A5 A6 A7 Ala AS A9
M1 M2
Wet Systems
DI/FF Systems
SD/FF Systems
Figure 47. HC1 emissions for continuous, intermittent, batch,
and pathological MWI's with add-on controls.
165
-------
The SD is a retention chamber, which allows the stoichiometric
ratio to be lower at Falicity M than at Facility A.
The HC1 removal efficiencies at facility J were relatively
low and were also not considered in establishing the HC1 emission
limits for the fabric filter systems. During the tests conducted
at this facility, nozzle plugging resulted in poor performance,
thereby invalidating these tests.
4.3.5 Sulfur Dioxide
Table 19 presents the SO2 emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 48 and 49 present the data used to establish
these emission limits.
TABLE 19. SO2 EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI'S
Control option
1-sec
2-sec
Wet systems15
FF/PBb
DI/FFb
SD/FFb
Fabric filter systems with carbon
injection"
SO? emission limits, ppmdv at 7 percent O%
Continuous, intermittent, batch
NAa
NAa
NAa
NAa
NAa
NAa
NAa
Pathological
NAa
NAa
NAa
NAa
NAa
NAa
NAa
aNo applicable limit.
"Includes 2-sec combustion.
4.3.5.1 Combustion Controls- -.SO^• Figure 48 presents S02
emission data for continuous, intermittent, and batch MWI's
burning general medical waste, and Figure 49 presents these data
for pathological MWI's. Because emissions of S02 are waste-
related, combustion controls do not reduce SO2-
4.3.5.2 Add-On Controls- -SO.-.. At the low inlet S02 levels
associated with MWI's, test data indicate that add-on controls
166
-------
150 -~~
140-
130 :
120 :
110-
100-
sr 90
o
70-
60-
50-
40-
30: *
20-
* *
~ * *
"» * *
I*
*
*
* * *
*
*
*
*
*
*
* * -
* *
K K K S
1233
Uncontrolled
WWW
1 2 3
1-sec comb.
AAAAAAAAAABJ JMM
123456718911212
a
2-sec combustion
Figure 48. SO, emissions for continuous, intermittent, and batch
MWI's with combustion controls.
167
-------
150
140
130
120
no
100
90
^80
j*
^*J5-
|GO
s
"50
30
20
10-
1
t
*
*
;
0-
Sl S2
Urartofed
Figure 49. S02 emissions for uncontrolled pathological MWI's
168
-------
are not effective in reducing these emissions. Therefore, S02
emission limits have not been established for these remaining
control technologies.
4.3.6 Lead
Table 20 presents the Pb emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 50 through 52 present the data used to develop
the emission limits.
TABLE 20 Pb EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
i^iouj-i *-w. _.__ —-.nTTrvT r\i~<-rr
-------
8
s
* * *
*
0
*
*
I ±
a
*
*
*
* *
*
*
*
*
f
K K K S
1233
Uncontrolled
WWW
1 2 3
1-sec comb.
AAAAAAAAABJJMM
13456718911212
a
2-sec combustion
Figure 50. Pb emissions for continuous, intermittent, and batch
MWI's with combustion controls.
170
-------
8-
7-
54
2-
1-
0-
SI S2
UrxoHrated
Figure 51. Pb emissions for uncontrolled pathological MWI's,
171
-------
I
IW WH^V
9"
8-
7-
'8 i
|
15
24
M A3 A5
Jl J2 Ml M2
Figure 52. Pb emissions for continuous, intermittent, batch, and
pathological MWI's with add-on controls.
172
-------
remaining control technologies use a fabric filter to control Pb
emissions. As is the case for PM, the Pb emission limit is based
on a constant outlet achievable with a fabric filter. Test data
from facilities A, J, and M indicate that fabric filter systems
can achieve a Pb level of 0.10 mg/dscm.
4.3.7 Cadmium
Table 21 presents the Cd emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 53 through 55 present the data used to develop
the emission limits.
TABLE 21. Cd EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI'S
Control option
1-sec
2-sec
Wet systems0
FF/PBC
DI/FF0
SD/FF0
Fabric filter systems with carbon
injection0
Cd emission limits, mg/dscm at 7 percent O2
Continuous, intermittent, batch
NAa
NAa
1.1
0.05
0.05
0.05
0.05
Pathological
NAb
NAb
0.10
0.05
0.05
0.05
0.05
aNo applicable limit. Highest 3-run average = 1.9 mg/dscm (facility A condition 8).
bNo applicable limit. Highest 3-run average = 0.17 mg/dscm (facility S condition 1).
°Includes 2-sec combustion.
4.3.7.1 Combustion Controls--Cd. Figure 53 presents the Cd
emission data for continuous, intermittent, and batch MWI's
burning general medical waste, and Figure 54 presents the data
for pathological MWI's. Because emissions of Cd are waste-
related, combustion controls do not reduce Cd emissions.
173
-------
3.6-
3.4-
3.2-
3.0-
2.8-
2.6-
2.4-
£22.
^ 2.0-
3.
•§• 1.8-
§ 1.6-
P ^
S 1.4;
1.2-
1.0-
0.8-
i
0.6-
0.44
*
H
0.2-
1
!
0.0^
fi 4
JL *
* 4
* 1 - * i *
* * T
*
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1233 123 134567
*
•
i
i
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i
j
I
T
t
T :* ~
t 1 ^r * *
*
Jt
4
*
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1-sec comb.
a
2-sec combustion
Figure 53. Cd emissions for continuous, intermittent, and batch
MWI's with combustion controls.
174
-------
3.6
3.2;
3.0-
1.6:
1.4-
\2-
1.0-
0.8 ;
0.6 -
0.4
02
0.0
SI 82
Unoonboled
Figure 54. Cd emissions for uncontrolled pathological MWI's.
175
-------
4.3.7.2 Add-On Controls--Cd. Figure 55 presents Cd removal
efficiencies and outlet levels achieved with the add-on control
technologies tested. The limit for wet systems is based on test
data from facility B, which indicate that wet systems are capable
of achieving at least 40 percent reduction in Cd emissions. The
remaining control technologies use a fabric filter to control Cd
emissions. As is the case for PM and Pb, the Cd emission limit
is based on a constant outlet achievable with a fabric filter.
Test data from facilities A, J, and M indicate that fabric filter
systems can achieve a Cd level of 0.05 mg/dscm.
4.3.8 Mercury
Table 22 presents the Hg emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 56 through 58 present the data used to develop
the emission limits.
TABLE 22. Hg EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI'S
Control option
1-sec
2-sec
Wet systems'3
FF/PBb
DI/FFb
SD/FFb
Fabric filter systems with carbon
injection
Hg emission limits, mg/dscm at 7 percent O2
Continuous, intermittent, batch
NAa
NAa
NAa
NAa
NAa
NAa
0.47C
Pathological
NAa
NAa
NAa
NAa
NAa
NAa
0.01°
*No applicable limit.
^Includes 2-sec combustion.
cThis emission limit corresponds to an 85 percent reduction.
4.3.8.1 Combustion ContrplsL-j^Hg. Figure 56 presents the Hg
emission data for continuous, intermittent, and batch MWI's
burning general medical waste, and Figure 57 presents this data
for pathological MWI's. Because emissions of Hg are waste-
related, combustion controls do not reduce Hg emissions.
176
-------
I
si
3,6"
3.4;
32;
3,0;
2,s;
2.6;
2.4;
22;
sr>°i
O i
t*\
1.41
5
*UM
0.4-
02
A1A3A5/16A7A1a
J1J2MlM2
Figure 55.
Cd emissions for continuous, intermittent, batch, and
pathological MWI's with add-on controls.
177
-------
26 ~
24-
22-
20-
18-
8
|14!
I12"
.s5
X 10 ->
f
8-
s
6- *
•i
4-- :
H ji
2-j -
t i
i '
1* - JL * | '
0-»- •*• * «• * *
K K K S W W V
1233 12C
* !
' 4
j
!
t
i . i
!
i
i
t
i
i
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t * ji
* '
V A A A A t
3 1 3 4 5 (
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t
• • • •
v
• :['• "l:;, ! • " • ' ::! " "" ",
' ,-l ! r '
* :
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i , . * • _
i -.."•
' * :• * *
I i * *
kAAAABJ JMM
5718911212
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1-see comb.
a
2-sec combustion
Figure 56. Hg emissions for continuous, intermittent, and
MWI's with combustion controls).
batch
178
-------
26-"
<
24;
22-
20;
H
18 J
S i
0-
81 82
Urcortrcted
Figure 57. Hg emissions for uncontrolled pathological MWI's.
179
-------
4.3.8.2 Add-On Controls--Hg. Test data from facilities A,
B, J, and M (wet systems and fabric filter systems without carbon
injection) showed no consistency in removing Hg emissions from
MWI's. Control of Hg is dependent on the presence of carbon at
relatively low temperature for a sufficient period of residence
time. There is not enough carbon in an MWI exhaust gas stream to
consistently reduce Hg. Therefore, emission limits have not been
established for these devices. On the other hand, as shown in
Figure 58, test data from facilities A and M show that injection
of activated carbon into fabric filter systems can achieve at
least 85-percent control of Hg. This reduction corresponds to
0.47 mg/dscm for a typical continuous, intermittent, or batch
unit; (85-percent reduction from a typical uncontrolled level of
3.1 mg/dscm) and an emission level of 0.01 mg/dscm for
pathological units (85-percent reduction from a typical
uncontrolled level of 0.05 mg/dscm). It is not known whether
carbon injection in a wet system will reduce Hg.
4.3.9 Nitrogen Oxides
Table 23 presents the NOX emission limits under each control
option for continuous, intermittent, batch, and pathological
MWI's. Figures 59 and 60 present the data used to establish
these emission limits.
4.3.9.1 Combustion Controls--NO.^. Figure 59 presents NOX
emission data for continuous, intermittent, and batch MWI's
burning general medical waste, and Figure 60 presents this data
for pathological MWI's. Because emissions of NOX are not
affected by increased residence time in the secondary chamber,
the 1-sec and 2-sec control options will not reduce emissions of
NOX.
4.3.9.2 Add-On Controls--NO^. None of the control systems
evaluated reduced NOX emissions. Therefore, NOX emission limits
have not been established for the add-on control technologies.
180
-------
100 -"
90-
f
*
80-
704
60-
rr so
S. 40
30-i
20
10-
0-
A8
A9
M2
Figure 58.
Fabric Filter w/ carbon
Hg emissions for continuous, intermittent, batch, and
pathological MWI's with add-on controls.
181
-------
TABLE 23. NOX EMISSION LIMITS FOR CONTINUOUS, INTERMITTENT,
BATCH, AND PATHOLOGICAL MWI'S
Control option
1-sec
2-sec
Wet systems13
FF/PBb
DI/FFb
SD/FFb
Fabric filter systems with carbon
injection"
NO^ emission limits, ppmdv at 7 percent C>2
Continuous, intermittent, batch
NAa
NAa
NAa
NAa
NAa
NAa
NAa
Pathological
NAa
NAa
NAa
NAa
NAa
NAa
NAa
aNo applicable limit.
''Includes 2-sec combustion.
182
-------
1000--
900
800
700-
«
?7 600-
O
500
400^
300
200
100
0-
*!*
K K K S
1233
Uncontrolled
Figure 59.
* t
***
*
WWW
1 2 3
1-sec comb.
AAAAAAAAAABJ JMM
123456718911212
a
2 - sec combustion
NOX emissions for continuous, intermittent, and batch
MWI's with combustion controls.
183
-------
1000
900
700-
500-
400 J
-*_
*
3004
200
SI
S2
Figure SO. NOX emissions for uncontrolled pathological MWI's.
184
-------
5.0 REFERENCES
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Chang, D., R. Mournighan, and G. Hoffman. Thermodynamic
Analysis of Post Flame Reactions Applied to Waste
Combustion. Land Disposal, Remedial Action, Incineration,
and Treatment of Hazardous Waste: Proceedings of the
Thirteenth Annual Research Symposium. EPA/600-9-87-015.
(NTIS PB87-233151).
McRee, R. Operation and Maintenance of Controlled-Air
Incinerators. Ecolaire Combustion Products. (Undated.)
Letter and attachments from T. Kendron, Simonds
Manufacturing Corp., to J. Farmer, EPA/ESD. April 9,
Response to Section 114 information request to MWI
manufacturers.
1990.
Ontario Ministry of the Environment. Incinerator Design and
Operating Criteria, Volume II - Biomedical Waste
Incineration. October 1986.
Barbeito, M., and M. Shapiro. "Microbiological Safety
Evaluation of a Solid and Liquid Pathological Incinerator."
Journal of Medical Primatology. pp. 264-273. 1977.
U. S. Environmental Protection Agency. Hospital Waste
Combustion Study: Data Gathering Phase, EPA-450/3-88-017.
December 1988.
U. S. Environmental Protection Agency. Municipal Waste
Combustion Study: Combustion Control of Organic Emissions,
EPA/530-SW-87-021C. (NTIS PB87-206090) June 1987.
Hasselriis, Floyd. "Minimizing Trace Organic Emissions from
Combustion of MSW by Use of Carbon Monoxide Monitors,"
presented at the ASME Solid Waste Processing Division
Conference, 1986.
Simonds Incinerators. Operation and Maintenance Manual for
Models 751B, 1121B, and 2151B. January 7, 1985.
John Zink Company. Standard Instruction Manual:
John Zink/Comtro A-22G General Incinerator and One-Halt
Cubic Yard Loader.
Letter from K. Wright, John Zink Company, to J. Eddinger,
U. S. Environmental Protection Agency. January 25, 1989.
Ecolaire Combustion Products, Inc. Equipment Operating
Manual for Model No. 480E.
Basic Environmental Engineering, Inc., Product literature.
Undated.
185
-------
14. Joy Energy Systems, Inc. Controlled-Air Incineration.
Product Literature. Undated.
15. Cleaver-Brooks. Operation, Maintenance, and Parts Manual,
Pyrolytic Incinerator. CBK_6826. September 1988.
16. Joseph, G. and D. Beachler. APTI course SI: 412C, Wet
Scrubber Plant Review - Self Instructional Guidebook.
EPA 450/2-82-020. March 1984. p. 1-3.
17. Perry, J.H. and C.H. Chilton, eds. Chemical Engineers'
Handbook, 5th ed. New York: McGraw-Hill Book Company.
1973. p. 20-95.
18. Reference 16, p. 1-4.
19. Reference 16, p. 1-5.
20. Reference 16, p. 1-7,
21. Reference 16, p. 1-8.
22. Andersen 2000, Inc. Emission Control Systems for
Incinerators. Bulletin TR 89-900239. February 1989.
p. 15.
23. Reference 16, p. 3-2.
24. U. S. Environmental Protection Agency. Operation and
Maintenance of Hospital Medical Waste Incinerators.
EPA-450/3-89-002. March 1989. p. 3-9.
25. Reference 22, p. 14.
26. Andersen 2000, Inc., Andersen Equipment Brochure. Bulletin
TR 81-90001 32 REV. B. Undated. p. 18.
27, Andersen 2000, Inc. Venturi and Packed Tower Scrubbing
Equipment. Engineering Manual with Operating and
Maintenance Instructions. [Model No. WAV-118 (variable
throat venturi)]. October 7, 1988. P. 2.
28. Reference 16, p. 3-3.
29. Brady, J., Andersen 2000, Inc., Economically and
Operationally Attractive Incinerator Emission Controls,
Undated, .p.. 21,
30. Reference 16, pp. 3-4, 3-5.
31. Reference 27, p. 7.
32. Reference 16, p. 3-6.
186
-------
33. Reference 16, p. 2-3.
34. Reference 16, p. 3-7.
35. Letter and attachments from D. Sanders, Andersen 2000, Inc.
to W. Maxwell, EPA/ISB. January 29, 1990. Response to
request for control equipment design and cost information.
36. Reference 24, pp. 3-9, 3-12.
37. Andersen 2000, Inc. Venturi Scrubbers for Fine Particulate
Control. Bulletin 78 900075 REV. B. December 1982.
pp. 6-7.
38. Reference 24, p. 3-9.
39. Telecon. M. Turner, MRI, with D. Sanders, Andersen 2000,
Inc. March 16, 1990. Design and operating parameters for
APCS.
40. Reference 24, p. 3-12.
41. Reference 22, p. 14.
42. Letter and attachments from H. Marschall, Emcotek Corp., to
W. Maxwell, U. S. Environmental Protection Agency. Product
literature. December 13, 1989.
43. Reference 16, p. 5-3.
44. Letter and attachments from S. Sheppard, The Ceilcote Co.,
to W. Maxwell, EPA/ISB. January 31, 1990. Response to
request for control equipment design and cost information.
45. Letter and attachments from A. Dozier, Advanced Concepts,
Inc., to W. Maxwell, EPA/ISB. January 21, and February 8,
1990. Response to request for control equipment design and
cost information.
46. Reference 22, p. 16.
47. Reference 16, p. 5-3.
48. Reference 16, p. 5-2.
49. Joseph, G. and D. Beachler. APTI Course 415, Control of
Gaseous Emissions - Student Manual. EPA 450/2-81-005.
December 1981, p. 4-22.
187
-------
50. Andersen 2000, Inc., Technical Description, Performance
Information, Material Balance and Flowsheet Data, Typical
Guarantees and Turnkey Installed Pricing for a 16.2 MM
BTU/hr (1,700 Ib/hr) State-Of-The-Art Medical Waste
Incinerator With Wet Scrubber Emission Controls. Workshop
on Medical Waste Management, Sacramento, CA. April 18-19,
1990. p> 10.
51. Marschall, H.L., et al, Emcotek Corp., New Oregon
Incinerator Demonstrates Process Innovations to Protect Both
Air and Water, presented at the AWMA Specialty Conference -
Thermal Treatment of Municipal, Industrial, and Hospital
Waste II (Pittsburgh, PA) and at the Pacific Northwest
International Section Annual Meeting (Spokane, WA).
November 1989.
52. Marschall, H.L., et al, Emcotek Corp., Comparison of
Commercial Gas Cleaning Systems Advanced Scrubber vs.
Baghouse For Hospital and Infections Waste Incinerators,
presented at the Second National Symposium on Infections
Waste Management. San Francisco, CA (September 19-23,
1988) and in Boston (October 3-7, 1988).
53. Marschall, H.L., et al, Emcotek Corp., Retrofitting Air
Pollution Controls to Existing Incinerators, presented at
the 82nd Annual Meeting of the Air and Waste Management
Association, Anaheim, CA. June 1989.
54. Ceilcote. IWS™ System, Air Pollution Control Division,
Technical Bulletin 12-19. December 1986.
55. Ensor, D. S., Ceilcote. Ionizing Wet-Scrubber Evaluation.
EPA-600/7-79-246. U. S. Environmental Protection Agency,
Research Triangle Park, North Carolina. November 1979.
56. Shifftner, K. and G. W. Burke. Incinerator Emissions
Control Using Wet Scrubbers. Presented at the Second Annual
National Symposium on Infectious Waste Management and
Incineration of Infectious Waste, San Francisco, California.'
September 19-23, 1988.
57. Holland, 0. L. and J. D. Means. Utilization of Hydro-Sonic®
Scrubbers for the Abatement of Emissions from Hazardous,
Industrial, Municipal, and Bio-Medical Wastes. Technical
Paper 7802. John Zink Company. Tulsa, Oklahoma, 1988.
58. Freeman, H. M. and R. A. Olexsey. Evaluation of Pilot-Scale
Pollution Control Devices for Hazardous Waste Incineration.
Paper 85-77.5. Presented at the 78th Annual Meeting of the
Air Pollution Control Association. Detroit, Michigan. June
1985.
188
-------
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
Letter and attachments from E. Mull, Jr., Interel Corp., to
W. Maxwell, U. S. Environmental Protection Agency.
January 30, 1990. Response to request for information from
air pollution control device vendors.
Letter and attachments from W. Wiley, Consumat Systems,
Inc., to W. Maxwell, U. S. Environmental Protection Agency.
March 19, 1990. Response to request for information from
air pollution control device vendors.
Letter and attachments from P. Finnis, Procedair Industrie
Corporation, to W. Maxwell, U. S. Environmental Protection
Agency. February 1, 1990. Response to request for ,
information from air pollution control device vendors.
Beachler, D., and M. Peterson. APTI Course SI:412A,
Baghouse Plan Review Student Guidebook. EPA 450/2-82-005. .
U. S. Environmental Protection Agency. April 1982.
U. S. EPA. Control Techniques for Particulate Emissions
from Stationary Sources, Volume I. EPA 450/3-81-005a.
U. S. Environmental Protection Agency. September 1982.
Letter and attachments from J. Childress, United McGill
Corporation, to W. Maxwell, U. S. Environmental Protection
Agency. February 9, 1990. Response to request for
information from air pollution control device vendors.
U. S. Environmental Protection Agency.
Maintenance Manual for Fabric Filters.
June 1986.
Operation and
EAP/625/1-86/020.
Richards Engineering. Air Pollution Source Field Inspection
Notebook; Revision 2. Prepared for the U. S. Environmental
Protection Agency, Air Pollution Training Institute.
June 16, 1988. p. 97.
Reference 49, p. 5-1.
Reference 49, p. 5-2.
Reference 24, p. 3-23.
Bundy, R. P., United McGill Corporation. Fabric Filter
Systems for Dry Acid Gas and Particulate Removal, presented
at the Incineration of Infectious Waste Conference. San
Francisco,. California (September 19-23, 1988) and in Boston
(October 3-7, 1988). p. 3.
71. Reference 66, p. 102.
189
-------
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82,
83,
84
85
Letter'and attachments from J. Hsieh, Research Cottrell Air
Pollution Control Division, to D. Wallace, Midwest Research
Institute. August 31, 1989. Information regarding the
performance of a dry injection fabric filter system
installed on a Skovde, Sweden, MWI.
Reference 66,
Reference 66,
Reference 24,
Reference 66,
Reference 66,
p. 99.
p. 98.
p. 3-24.
p. 101.
p. 100.
Reference 66, pp. 100-101.
U. S. Environmental Protection Agency, Municipal Waste
Combustors--Background Information for Proposed Standards:
Post-Combustion Technology Performance. EPA-450/3-89-27C.
August 1989. p. 6-2.
Jorgensen, C., Acurex Corp., Assessment of Flue Gas Cleaning
Technology for Municipal Waste Combustion. September 1986.
pp. 16-31.
Reference 66, p. 115.
U. S. Environmental Protection Agency, Municipal Waste
Combustion Study: Flue Gas Cleaning Technology.
EPA/530-SW-87-021d. June 1987. p. 4-14.
Memo from D. Wallace, MRI, to R. Copland, EPA/ESD/SDB.
Emissions from Pathological MWI's. March 30, 1992.
SO.
Michigan Hospital Incinerator Emissions Test Program; Volume
II: Site Summary Report, Borgess Medical Center
Incinerator. Energy and Environmental Research Corporation.
Prepared for Michigan Department of Commerce and U. S.
Environmental Protection Agency, Research Triangle Park, NC.
August 13, 1991.
Medical Waste Incineration Emission Test Report for Borgess
Medical Center, Kalamazoo, MI; Volume I, Volume II:
Appendices A-C, and Volume III: Appendices D-I. Radian
Corporation. Prepared for U. S. Environmental Protection
Agency, Research Triangle Park, NC. January 1992.
190
-------
86. Michigan Hospital Incinerator Emissions Test Program;
Volume III: Site Summary Report, University of Michigan
Medical Center Incinerator. Energy and Environmental
Research Corporation. Prepared for Michigan Department of
Commerce and U. S. Environmental Protection Agency, Research
Triangle Park, NC. August 13, 1991.
87. Medical Waste Incineration Emission Test Report for Jordan
Hospital, Plymouth, MA; Volume I-III. Radian Corporation.
Prepared for U. S. Environmental Protection Agency, Research
Triangle Park, NC. EMB Report 90-MWI-6. February 1991.
88. Medical Waste Incineration Emission Test Report for Lenoir
Memorial Hospital, Kinston, NC; Volumes I-II. Radian
Corporation. Prepared for U. S. Environmental Protection
Agency, Office of Solid Waste, Washington, DC. May 1990.
89. Medical Waste Incineration. -Emission Test Report for
Morristown Memorial Hospital, Morristown, NJ; Volume I and
Volume II: Appendices. Radian Corporation. Prepared for
U. S. Environmental Protection Agency, Research Triangle
Park, NC. February 1992.
90. Medical Waste Incineration Emission Test Report for AMI
Central Carolina Hospital, Sanford, NC; Volumes I-II.
Radian Corporation. Prepared for U. S. Environmental
Protection Agency, Office of Solid Waste, Washington, DC.
EMB Report 90-MWI-5. December 1991.
91. Medical Waste Incineration Emission Test Report for Cape
Fear Memorial Hospital, Wilmington, NC; Volumes I-II.
Radian Corporation. Prepared for U. S. Environmental
Protection Agency, Office of Solid Waste, Washington, DC.
EMB Project No. 90-MWI. November 1990.
92. Telecon. Maxwell, W., U. S. Environmental Protection
Agency, with Hadley, H., B.G. Wickberg Co., Inc. April 23,
1992. MWI emission test at Jordan Hospital, Plymouth, MA.
191
-------
-------
APPENDIX A.
SUMMARY OF TEST PROGRAM OPERATING DATA
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TABLE A-3. APCD OPERATING PARAMETERS FOR FACILITY B
Test
MM1 1622
MM1 3624
MM1 4626
MM1 5627
Condition
1
1
1
1
Scrubber
inlet
temp., °F
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543
541
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31
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aData not measured.
A-7
-------
TABLE: A-4. APCD OPERATING PARAMETERS AT FACILITY j
Test
Jl BR305
J2 BD305
J3 BA307
J4 BD307
J5 BR309
J6 BD309
Condition
1
2
1
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1
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373
371
375
374
376
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134
136
135
133
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in H,0
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APPENDIX B.
TEST PROGRAM EMISSION DATA SUMMARY
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TABLE B-2. POST-COMBUSTION EMISSION CONCENTRATIONS FOR
CDD/CDF AND METALSa
Facility
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
B
B
B
B
Test
MB1 1523
MB1 2524
MB1 3531
MB3 1505
MB3 2507
MBS 3508
EB1 1517
EB1 2518
EB1 3521
EB1 4522
EB1 5525
MB131502
MB132515
EB6 1426
EB6 2427
EB6 3430
EB7 1509
EB7 2511
EB7 3514
EB7 4516
EB8 1529
EB8 2530
EB8 3601
B2 90791
B3 90991
B4 91091
B5 91191
B6 91291
B7 91391
B8 91491
B9 91691
MM1 1622
MM1 3624
MM1 4626
MM1 5627
Condition
1
1
1
2
2
2
3
3
3
3
3
4
4
5
5
5
6
6
6
6
7
7
7
1A
1A
1A
8
8
9
9
9
1
1
1
1
CDD/CDF, ng/dscm
665
410
394
229
531
505
250
b
485
b
318
b
271
b
b
b
691
317
b
553
319
484
574
158
274
279
306
517
471
429
347
1,554
1,388
1,411
. b
Cd, ng/dscm
365
283
358
b
b
b
343
b
729
603
b
143
420
144
102
190
260
329
263
211
190
201
239
396
364
446
346
3,520
241
1,210
690
498
285
373
b
Pb, ng/dscm
3,441
2,928
3,530
b
b
b
3,730
b
3,509
2,994
b
2,155
2,549
4,911
4,625
6,534
6,855
7,642
8,629
3,927
4,685
5,156
5,766
952
2,180
1,377
2,600
1,620
459
2,280
1,760
3,810
2,620
3,520
b
Hg, ng/dscm
18,007.9
11,715.5
5,992.2
b
b
b
14,848.5
b
25,708.3
8,403.2
b
363.5
43.1
402.0
3,012.5
238.9
9,960.8
154.6
842.7
4,816.3
1,891.0
1,906.1
116.7
9,580.0
7,300.0
3,770.0
6,300.0
8,460.0
8,479.8.
6,830.0
13,200.0
167.0
414.0
516.0
b
1-4
-------
TABLE B-2. (continued)
Facility
J
J
J
J
J
J
K
K
K
K
K
K
K
K
K
M
M
M
M
M
M
S
S
S
S
S
S
S
S
S
W
w
W
w
Test
Jl BR305
J2 BD305
J3 BR307
J4 BD307
J5 BR309
36 BD309
LM4 602
LM4R 604
LM6 605
LM1 530
LM2 531
LM3 601
LM7_606
LM8 607
LM9 608
MW1 1118
MW2_1119
MW3 1120
MW4_1121
MW5 1122
MW6 1123
CC1_920
CCS 922
CC10 102
CCS 924
CC6 925
CC9 928
CC2 921
CC4 923
CCS 927
CF1 815
CF5 821
CF6_822
CF2_818
Condition
1
2
1
2
1
2
1
1
1
2
2
2
3
3
3
1
1
1
2
2
2
1
1
1
2
2
2
3
3
3
1
1
1
2
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4
5
3
599
94
3,036
4,818
b
6,325
3,247
8,336
10,213
48,571
27,769
30,243
144
129
301
242
292
63
279
1,994
468
427
157
1,144
12,728
40,969
20,457
3,084
3,562
539
4,070
Cd, /tg/dscm
44
152
23
252
22
216
b
163
173
110
392
140
430
478
202
494
369
548
524
402
549
16
504
<1
13
26
22
55
42
67
296
336
209
333
Pb, /ig/dscm
718
5,187
634
5,028
1,063
6,412
b
7,012
1,549
1,316
1,855
2,439
3,482
2,121
2,416
3,801
3,570
3,590
4,250
4,730
4,260
512
814
0
329
202
389
2,380
1,210
2,050
4,754
6,372
2,864
4,476
Hg, /tg/dscm
527.0
654.0
2,862.0
8,620.0
383.0
908.0
b
208.8
75.6
152.3
124.5
139.7
5,926.0
85.4
172.4
2,200.0
643.0
4,930.0
2,420.0
2,240.0
3,220.0
4.3
<0.9
116.2
182.5
<0.7
<0.5
10.7
5.2
-0.7
286.3
120.0
146.4
613.0
B-5
-------
TABLE B-2. (continued)
Facility
W
W
W
W
W
Test
CF3 819
CF4 820
CF7 826
CF8 827
CF9 828
Condition
2
2
3
3
3
CDD/CDF, ng/dscm
8,102
5,671
5,215
2,679
7,198
Cd, fig/dscm
461
361
731
619
401
Pb, ng/dscm
7,537
6,741
4,316
7,710
4,008
Hg, ng/dscm
880.7
35.7
6,543.4
939.4
432.7
aAll concentrations corrected to 7 percent
"Data not measured.
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B-8
-------
APPENDIX C.
GRAPHS OF POST-COMBUSTION EMISSION DATA
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-------
-------
APPENDIX D.
GRAPHS OF POST-APCS EMISSION CONCENTRATIONS
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-------
TECHNICAL REPORT DATA
(Please read Instructions on reverse before completing)
i. REPORT NO.
EPA-453/R-94-044a
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Medical Waste Incinerators - Background Information for
Proposed Standards and Guidelines: Control Technology
Performance Report for New and Existing Facilities
5. REPORT DATE
July 1994
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Emission Standards Division (Mail Drop 13)
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D1-0115
42. SPONSORING AGENCY NAME AND ADDRESS
Director
Office of Air Quality Planning and Standards
Office of Air and Radiation
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/200/04
15. SUPPLEMENTARY NOTES
Published in conjunction with proposed air emission standards and guidelines for
medical waste incinerators
16. ABSTRACT
This report describes the various emission control technniques used to control emissions from
medical waste incinerators (MWI's), summarizes the emission test data generated during a
comprehensive EPA emission test program, and provides an emission test data analysis that quantifies
the performance of these techniques. This is one in a series of reports used as background information
in developing air emission standards and guidelines for new and existing MWI's.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Pollution Control
Standards of Performance
Emission Guidelines
Medical Waste Incinerators
Air Pollution Control
Solid Waste
Medical Waste
Incineration
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Report)
Unclassified
21. NO. OF PAGES
233
20. SECURITY CLASS (Page)
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE
-------
------- |