United States Air and Energy Engineering EPA-600/8-89-058
Environmental Protection Research Laboratory August 1989
Agency Research Triangle Park, NC 27711
Research and Development _^__^_
Municipal Waste
Combustion
Assessment:
Combustion Control
at Existing Facilities
Prepared For
Office of Air Quality Planning and Standards
Prepared By
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
This document is printed on recycled paper
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EPA-600/8-89-058
August 1989
MUNICIPAL WASTE COMBUSTION ASSESSMENT:
COMBUSTION CONTROL AT EXISTING FACILITIES
Prepared by
P.J. Schindler
Energy and Environmental Research Corporation
3622 Lyckan Parkway. Suite 5006
Durham, NC 27707
Under Contract No. 68-03-3365
Work Assignment No. 1-05
EPA Project Officer: James D. Kilgroe
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
Prepared for
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
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REVIEW NOTICE AND DISCLAIMER
The information in this document has been funded wholly by the United
States Environmental Protection Agency under Contract No. 68-03-3365 to Energy
and Environmental Research Corporation. It has been subject to the Agency's
peer and administrative review (by both the Office of Research and Development
and the Office of Air Quality Planning and Standards), and it has been
approved for publication as an Agency document. Mention of trade names or
commercial products does not constitute endorsement or recommendation of a
commercial product by the Agency.
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ABSTRACT
The EPA's Office of Air Quality Planning and Standards (OAQPS) is
developing emission standards and guidelines for new and existing municipal
waste combustors (MWCs) under the authority of Sections lll(b) and lll(d) of
the Clean Air Act (CAA). The EPA's Office of Research and Development (ORD)
is providing support in developing the technical basis for good combustion
practice (GCP), which is included as a regulatory alternative in the standards
and guidelines. This report provides the supporting data and rationale used
to establish baseline emission levels for model plants that represent portions
of the existing population of MWCs. The baseline emissions were developed
using the existing MWC data base or. in cases where no data existed,
engineering judgement. The baseline emissions represent performance levels
against which the effectiveness and costs of emission control alternatives can
be evaluated. An assessment of potential combustion retrofit options was
developed and applied to each model plant, and emission reduction estimates
were made for each retrofit application. This report provides the rationale
used to estimate the emission reductions associated with each combustion
retrofit.
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FOREWORD
Based upon its analysis of Municipal Waste Combustors (MWCs), the
Environmental Protection Agency (EPA) has determined that MWC emissions may
reasonably be anticipated to contribute to the endangerment of public health
and welfare and warrant further regulation. As a result, EPA's Office of Air
Quality Planning and Standards is developing emission standards for new MWCs
under Section lll(b) of the Clean Air Act (CAA) and guidelines for existing
MWCs under Section lll(d) of the CAA.
In support of these regulatory development efforts, the Air and Energy
Engineering Research Laboratory in EPA's Office of Research and Development
has conducted an in-depth assessment of combustion control practices to
minimize air emissions from MWCs. The results of this assessment are
documented in the following reports:
Municipal Waste Combustion Assessment: Combustion Control at New
Facilities. August 1989 (EPA-600/8-89-057)
Municipal Waste Combustion Assessment: Combustion Control at
Existing Facilities, August 1989 (EPA-600/8-89-058)
Municipal Waste Combustion Assessment: Fossil Fuel Co-Firing,
July 1989 (EPA-600/8-89-059)
Municipal Waste Combustion Assessment: Waste Co-Firing, July 1989
(EPA-600/8-89-060)
Municipal Waste Combustion Assessment: Fluidized Bed Combustion,
July 1989 (EPA-600/8-89-061)
Municipal Waste Combustion Assessment: Medical Waste Combustion
Practices at Municipal Waste Combustion Facilities, July 1989 (EPA-
600/8-89-062)
Municipal Waste Combustion Assessment: Technical Basis for Good
Combustion Practice, August 1989 (EPA-600/8-89-063)
Municipal Waste Combustion, Multi-Pollutant Study, Emission Test
Report. Maine Energy Recovery Company, Refuse-Derived Fuel
Facility, Biddeford, Maine, Volume I, Summary of Results, July
1989 (EPA-600/8-89-064a)
Municipal Waste Combustion, Multi-Pollutant Study, Emission Test
Report, Mass Burn Refractory Incinerator, Montgomery County South,
Ohio, Volume I, Summary of Results, August 1989 (EPA-600/8-89-
065a)
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The specific objectives of this document, "Municipal Waste Combustion
Assessment: Combustion Control at Existing Facilities," are to present the
data and supporting rationale used to establish baseline emission estimates
for a set of MWC model plants, and to provide the rationale for estimating
emission reductions that result from combustion retrofit alternatives
developed for each model plant. The model plants represent various classes of
MWCs that will be regulated by the Section lll(d) emission guidelines.
iv
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CONTENTS
SECTION PAGE
1.0 SUMMARY 1-1
2.0 BACKGROUND 2-1
3.0 MODEL PLANT PERFORMANCE ESTIMATES 3-1
3.1 Mass Burn Waterwall MWCs 3-2
3.1.1 Large Mass Burn Waterwall MWCs 3-4
3.1.2 Mid-Size Mass Burn Waterwall MWCs 3-16
3.1.3 Small Mass Burn Waterwall MWCs 3-24
3.2 Refuse-Derived-Fuel Fired Spreader Stoker MWCs 3-38
3.2.1 Albany, New York 3-42
3.2.2 Niagara Falls. New York 3-46
3.2.3 Lawrence, Massachusetts 3-46
3.2.4 Biddeford. Maine 3-47
3.2.5 Red Wing, Minnesota 3-47
3.2.6 Baseline Emission Estimates 3-48
3.2.7 Combustion Modifications 3-50
3.3 Mass Burn Refractory Wall MWCs 3-50
3.3.1 Emissions Data 3-53
3.3.2 Baseline Emission Estimates 3-55
3.3.3 Combustion Modifications 3-56
3.4 Mass Burn Modular Starved Air MWCs 3-56
3.4.1 Emissions Data 3-60
3.4.2 Baseline Emission Estimates 3-67
3.4.3 Combustion Modifications 3-67
3.5 Mass Burn Modular Excess Air MWCs 3-69
3.5.1 Emissions Data 3-69
3.5.2 Baseline Emission Estimates 3-76
3.5.3 Combustion Modifications 3-76
3.6 O'Connor Rotary Waterwall MWCs 3-76
3.6.1 Emissions Data 3-79
3.6.2 Baseline Emission Estimates 3-79
3.6.3 Emission Reductions Resulting from Combustion
Modifications 3-81
4.0 REFERENCES 4-1
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FIGURES
FIGURE PAGE
3-1 Large Mass Burn Waterwall - Baseline Determination 3-13
3-2 Large Mass Burn Waterwall - Stack Emission Data 3-15
3-3 Mid-Sized Mass Burn Waterwall - Baseline Determination 3-23
3-4 Small Mass Burn Waterall - Baseline Determination 3-32
3-5 Quebec City MWC - Pre-Modification (1978 Design) 3-33
3-6 Quebec City MWC - Post-Modification (1986 Design) 3-35
3-7 Comparison of Stack Test Results - Quebec City MWC 3-39
3-8 Combustion Control - Small Mass Burn Waterwall 3-40
3-9 RDF Combustors - Baseline Determination 3-49
3-10 Mass Burn Refractory - Baseline Determination 3-54
3-11 Combustion Control - Refractory 3-57
3-12 Prince Edward Island MWC 3-64
3-13 Mass Burn Modular Starved Air - Baseline Determination 3-68
3-14 Pittsfield, MA Modular Excess Air MWC 3-71
3-15 Mass Burn Modular Excess Air - Baseline Determination 3-77
TABLES
TABLE PAGE
1-1 lllCd) Model Plants 1-2
1-2 lll(d) Baseline Emissions 1-3
1-3 lll(d) Emissions Resulting from Combustion Modifications 1-4
2-1 Combustion Guidelines for MWCs 2-3
3-1 Existing Mass Burn Waterwall MWCs 3-3
3-2 Large Mass Burn Waterwall MWCs - Performance Assessment 3-5
3-3 Data Summary - Westchester County Parametric Test 3-10
3-4 Midsize Mass Burn Waterwall MWCs - Performance Assessment 3-17
3-5 CDD/CDF Emissions History - Hampton. VA MWC 3-25
3-6 Small Mass Burn Waterwall MWCs - Performance Assessment 3-26
3-7 Quebec City Parametric Test - Emissions Summary 3-37
3-8 Existing RDF Combustors 3-41
3-9 RDF Fired Spreader Stokers - Performance Assessment 3-43
3-10 Existing Mass Burn Refractory Wall Combustors 3-51
3-11 Existing Modular Starved Air Combustors 3-58
3-12 Modular Starved Air MWCs - Performance Assessment 3-61
3-13 Performance Test Data - Prince Edward Island MWC 3-65
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3-14 Existing Modular Excess Air Combustors 3-70
3-15 Pittsfield, MA Modular Excess Air MWC Emissions Test Data 3-72
3-16 Existing Rotary Waterwall Combustors 3-78
3-17 Mass Burn Rotary Waterwall MWCs - Performance Assessment 3-80
VI 1
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1.0 SUMMARY
The EPA has completed a study which characterizes the emission
performance of the existing population of municipal waste combustors (MWCs)
and evaluates the technical feasibility and costs of applying retrofit
controls to existing MWCs.1 Twelve model plants were developed in this study
which represent classes or groups of combustors in the existing MWC population
that will be subject to the lll(d) guidelines. Baseline emission performance
estimates were established for each of the model plants. A number of retrofit
control alternatives, including combustion controls and various add-on
controls, were applied to each model, and emission reduction and cost
estimates were made for each control alternative. This report provides data
and supporting rationale used to establish the baseline emission levels for
each model plant and documents the basis for the estimated emission reductions
associated with the application of combustion controls.
Table 1-1 presents design and operating data for the twelve lll(d) model
plants, including combustor type, number of combustors per plant, unit size.
total plant size, and heat recovery practices. Baseline emission levels were
established for five air pollutants for each model:
• polychlorinated dibenzo-p-dioxin and dibenzofuran (CDD/CDF)
• carbon monoxide (CO)
• particulate matter (PM)
• hydrogen chloride (HC1)
• sulfur dioxide (SO?)
Baseline emission levels are expressed as flue gas concentrations measured at
the combustor or boiler outlet location, prior to treatment by add-on flue gas
cleaning equipment. Unless otherwise noted, all emissions are normalized to 7
percent 0? . Table 1-2 summarizes the baseline emissions that were developed
for each model plant, and Table 1-3 presents the estimated emission levels
achieved with the application of good combustion controls.
Baseline emissions for all pollutants except acid gases (HC1 and
were established using the available MWC emissions data base, or in cases
where little or no data exist, engineering judgement. Emissions of HC1 and
are dependent on waste feed characteristics. It was assumed that baseline
1-1
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TABLE 1-1. lll(D) MODEL PLANTS
MODEL
NO. COMBUSTOR TYPE
1 Mass burn refractory wall -
traveling grate
2 Mass burn refractory wall -
rocking grate
3 Mass burn refractory wall -
split flow
4 Mass burn waterwall - large
5 Mass burn waterwall - midsize
6 Mass burn waterwall - small
7 RDF spreader stoker - large
8 RDF spreader stoker - small
9 Mass burn modular starved
air - large
10 Mass burn modular starved
air - small
11 Mass burn modular excess air
12 Mass burn rotary waterwall
UNIT SIZE
tpd Mg/day
375 341
120 109
300 273
750 682
360 327
100 91
1000 909
300 273
50 45
25 23
100 91
250 227
# OF
UNITS
2
2
3
3
3
2
2
2
3
2
2
2
TOTAL
PLANT CAPACITY
tpd Mg/day
750 682
240 218
900 818
2250 2045
1080 982
200 182
2000 1818
600 545
150 136
50 45
200 182
500 455
HEAT
RECOVERY
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
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TABLE 1-2. lll(D) BASELINE EMISSIONS
MODEL
NO. COMBUSTOR TYPE
1 Mass burn refractory wall -
traveling grate
2 Mass burn refractory wall -
rocking grate
3 Mass burn refractory wall -
spl it f 1 ow
4 Mass burn waterwall - large
5 Mass burn waterwall - midsize
6 Mass burn waterwall - small
7 RDF spreader stoker - large
8 RDF spreader stoker - small
9 Mass burn modular starved
air - large
10 Mass burn modular starved
air - smal 1
11 Mass burn modular excess air
12 Mass burn rotary waterwall
CDD/CDF
(ng/dscm)
4000
4000
4000
500
200
2000
2000
2000
400
400
200
2000
CO
(ppmv)
500
500
500
50
50
400
200
200
100
100
50
100
PM
(mg/dscm)
6900
(3 gr/dscf)
6900
6900
4600
(2 gr/dscf)
4600
4600
9200
(4 gr/dscf)
9200
345
(0.15 gr/dscf)
345
4600
4600
HC1
(ppmv)
500
500
500
500
500
500
500
500
500
500
500
500
S02
(ppmv)
200
200
200
200
200
200
300
300
200
200
200
200
I
00
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TABLE 1-3. lll(D) EMISSIONS RESULTING FROM COMBUSTION MODIFICATIONS
MODEL
NO. COMBUSTOR TYPE
1 Mass burn refractory wall -
travel ing grate
2 Mass burn refractory wall -
rocking grate
3 Mass burn refractory wall -
split flow
4 Mass burn waterwall - large
5 Mass burn waterwall - midsize
6 Mass burn waterwall - small
7 RDF spreader stoker - large
8 RDF spreader stoker - small
9 Mass burn modular starved
air - large
10 Mass burn modular starved
air - small
11 Mass burn modular excess air
12 Mass burn rotary waterwall
CDD/CDF
(ng/dscm)
500
500
500
500
200
200
1000
1000
400
400
200
400
CO
(ppmv)
150
150
150
50
50
50
150
150
100
100
50
100
PM
(mg/dscm)
6900
(3 gr/dscf)
6900
6900
4600
(2 gr/dscf)
4600
4600
9200
(4 gr/dscf)
9200
345
(0.15 gr/dscf)
345
4600
4600
HC1
(ppmv)
500
500
500
500
500
500
500
500
500
500
500
500
S02
(ppmv)
200
200
200
200
200
200
300
300
200
200
2CO
200
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HC1 and SO? emissions, when expressed on a concentration basis, are identical
for combustors burning a given waste type. Two model plants, both refuse-
derived-fuel (RDF) spreader stokers, burn processed waste. All other model
plants burn raw, unprocessed municipal solid waste (MSW). Waste ultimate
analyses are included for both fuels in the lll(d) technical support
document, i
The goals of this report are to present the data and supporting
rationale used to establish the emission concentrations in Tables 1-2 and 1-3.
Section 2 provides background information describing the approach used in the
model plant study, and Section 3 provides the rationale and data used to
establish the baseline emissions and emission reduction estimates for each
model plant.
1-5
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2.0 BACKGROUND
On July 7, 1987, EPA published an Advance Notice of Proposed Rulemaking
(ANPR) which announced EPA's intent to develop new source performance
standards (NSPS) for new MWCs, and emission guidelines for existing MWCs under
the authority of Section lll(d) of the Clean Air Act.2 All plants that
commence construction after the proposal date will be subject to the NSPS and
all plants not subject to the NSPS are regulated by the guidelines. Section
lll(d) requires that States submit plans to EPA describing the regulatory
approach that will be implemented at existing facilities to ensure compliance
with the guidelines. The plans are reviewed and approved by EPA and are
implemented by the States.
Prior to the regulatory decision in July 1987, the majority of EPA's
data gathering efforts were focused on the performance of new MWCs. It was
determined that additional data were needed to assess the emission performance
of existing MWCs and to provide guidance for retrofit applications. As a
result. EPA developed and funded a study intended to:
1) Estimate baseline emission levels for model plants representing
various groups of MWCs in the existing population.
2) Develop retrofit alternatives to reduce baseline emissions.
3) Estimate emission reductions associated with each retrofit
alternative.
4) Develop cost estimates for each retrofit alternative.
The retrofit alternatives that were evaluated include modifications to the
combustion process and retrofit of flue gas cleaning equipment. This
memorandum documents the rationale for the model plant baseline emission
estimates and the estimated emission reductions resulting from the application
of combustion retrofits. A separate report has been developed to address
performance levels associated with add-on controls.3
The background information that led to the MWC regulatory decision was
compiled and published in a Report to Congress.4 As part of this effort,
preliminary recommendations were made defining good combustion practices for
new mass burn waterwall, modular starved air. and refuse-derived-fuel (RDF)
fired MWCs.5 Good combustion practices are expected to minimize emission of
2-1
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organics from MWC systems. The original recommendations included three
elements:
• Design
• Operation/Control
• Verification
The requirements to satisfy these elements are:
• MWCs must be designed in a manner that minimizes air emissions.
• MWCs must be operated within an envelope dictated by the design of
the combustion system, and controls must be in place to prevent
operation outside of the established operating envelope.
• The performance of the combustion system must be verified by way
of compliance testing and through continuous monitoring of key
design and operating parameters, such as combustion air flows, gas
temperatures. CO flue gas concentrations, and 02 flue gas
concentrations.
The good combustion recommendations were developed primarily to provide a set
of criteria against which the performance of new MWCs could be evaluated.
However, the recommendations can also be used to evaluate the performance of
existing MWCs by identifying design and operating features which could
potentially be modified to improve emissions performance. The revised
recommendations for good combustion practices used in this report are
presented in Table 2-1. The revised recommendations are similar to those
provided in the Report to Congress, with the exception of changes in some of
the CO emission limits and the addition of a recommendation on PM control
device temperature to address low temperature formation of CDD/CDF.
The good combustion practices defined in this report are designed to:
(1) maximize in-furnace destruction of organic compounds, and (2) minimize
conditions that lead to low temperature formation of CDD/CDF. Conditions
within the combustion process that satisfy the first goal include:
• Mixing of fuel and air to minimize the existence of long-lived.
fuel-rich pockets of combustion products.
2-2
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TABLE 2-1. GOOD COMBUSTION PRACTICES FOR MINIMIZING TRACE ORGANIC
EMISSIONS FROM MUNICIPAL WASTE COMBUSTORS
DESIGN
Temperature at fully
mixed height
Underfire air control
Overfire air capacity (not
an operating requirement)
Overfire air injector
design
Auxiliary fuel capacity
Downstream flue gas
temperature
1800°F (982°C)
At least 4 separately adjustable plenums.
One each under the drying and burnout zones
and at least two separately adjustable
plenums under the burning zone (MB/WW). As
required to provide uniform bed burning
stoichiometry (RDF)
40% of total air (MB/WW. RDF)
80% of total air (MOD/SA)
That required for penetration and coverage
of furnace cross-section
That required to meet start-up temperature
and 1800°F (982°C) criteria under part-load
conditi ons
<450°F «232°C) at PM control device
in! et
OPERATION/CONTROL
Excess air
Turndown restrictions
Start-up procedures
Use of auxi1iary fuel
6-12% oxygen in flue gas (dry basis) (MB/WW
and MOD/SA). 3-9% oxygen in flue gas (dry
basis) (RDF)
80-110% of design - lower limit may be
extended with verification tests
On auxiliary fuel to design temperature
On prolonged high CO or low furnace
temperature
VERIFICATION
Oxygen in flue gas
CO in flue gas
Furnace temperature
Adequate air distribution
Downstream flue gas
temperature
Monitor
Monitor - 50 ppm on 4 hour average.
corrected to 7% 02 (MB/WW and MOD/SA). 100
ppm at 7% 02 (RDF)
Monitor - minimum of 1800°F (982°C) (mean)
at fully mixed height across furnace
Verification Tests
Monitor - <450°F «232°C) at PM control
device inlet
MB/WW - mass burn waterwall
MOD/SA - modular starved air
2-3
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• Attainment of sufficiently high temperatures in the presence of
oxygen for the destruction of hydrocarbon species,
• Prevention of quench zones or low temperature pathways that will
allow partially reacted fuel (solid or gaseous) to exit the
combustion chamber.
All of these conditions are interrelated; successful destruction of trace
organic species requires that all three conditions be satisfied in the MWC
system. Mixing is not sufficient unless it is achieved at temperatures that
assure thermal destruction of organic compounds. Completion of the mixing
process at adequate destruction temperatures prevents escape of combustibles
through low temperature pathways. Despite the continuing advancements made in
combustion control, perfect mixing will never be achieved in a combustion
system, whether conventional or waste fired. As a result, zero organic
emissions will not occur. The goal of good combustion practice is to provide
the conditions that will minimize air emissions of concern.
One important component which was not explicitly included in the
original GCP recommendations addresses the potential for low temperature
formation of CDD/CDF. These formation phenomena have been measured at several
full scale MWCs, including the Prince Edward Island; Pittsfield, MA; North
Andover, MA.; and PineTlas County, FL. faci 1 i ties. 6.7.8,9 Further discussion of
test data from these plants is included in Section 3.0 of this report.
The discovery of CDD/CDF formation in full scale MWCs has prompted
research in the laboratory to identify the parameters controlling low
temperature CDD/CDF formation reactions. Bench scale experiments indicate
that, under excess air conditions, CDD/CDF formation occurs on the surface of
fly ash at temperatures ranging from approximately 200 to 400°C (392 to
752°F), with the maximum formation occurring near 300°C (572°F).i°
Conversely, research results have indicated that when the same experiments
were performed in an oxygen-deficient atmosphere, dechlorination of CDD/CDF
compounds occurred.11 The current thinking regarding these findings is that
the formation process may involve catalytic reactions of organic precursor
compounds with particulates containing metallic species such as copper
chloride (CuClz). The bench scale studies indicate that the rate of CDD/CDF
formation and/or chlorination is affected by a number of parameters; including
2-4
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temperature, residence time, catalyst effects, carbon content, oxygen
concentration, and moisture. Results from these experiments provide
information which can be transferred to full scale MWCs in order to develop
control strategies for minimizing CDD/CDF formation.
Although many strategies for minimizing the reactions (i.e.. catalyst
poisons) remain to be investigated, it appears at this time that an initial
control strategy is to minimize the particulate matter concentration and the
flue gas residence time at temperatures were the rate of CDD/CDF formation is
highest. If organic precursor materials leaving the combustor are minimized
and if flue gas retention times and PM concentrations can be minimized in the
200 to 400°C (392 to 752°F) temperature range, it appears that the formation
process can be minimized. Many existing MWCs currently operate flue gas
cleaning equipment (ESPs) in this temperature window. The increased gas
residence time and PM concentrations which occur in the ESP may be the primary
cause of CDD/CDF formation, leading to increased emissions in the stack.
Recent data from a full scale MWC confirm that high efficiency ESPs operating
at temperatures below 250°C actually provide significant CDD/CDF removal.12
Based on these considerations, a new component of the good combustion
practices was developed. The recommendation is to maintain PM control device
inlet gas temperatures below 232°C (450°F).
As part of an information gathering effort in the MWC Retrofit Study,
site visits were made to 12 MWCs that were judged to be representative of the
major combustor classes in the existing population. Additional emissions data
and design and operating information obtained through information requests
were also used to characterize the performance of the existing MWC population.
After review of all available information was completed, model plant
configurations and baseline emission performance estimates were established.
The design, operation/control, and monitoring features of each model
plant were evaluated relative to the good combustion practice recommendations.
If emission levels for a model plant were relatively low, verification
measures were in place, and the potential for reducing emissions through
additional combustion modifications was questionable, then good combustion
practices were judged to be in place for the model plant. If these criteria
were not met. then additional evaluation of design and operating practices was
required, and modifications were prescribed to correct any design and/or
operating deficiencies. In a few cases, the modifications required only the
2-5
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addition of verification measures (e.g.. CO monitors) to satisfy the good
combustion practice recommendations.
Several model plants required more extensive analysis. In these cases.
the following types of questions were raised regarding model performance:
• Is the system designed and operated to meet the required furnace
temperature at the fully mixed location? What design and
operating constraints prevent attainment of the required
temperature?
• Are the waste feed system and underfire (primary) air control
adequate to provide uniform stoichiometries in the primary
combustion zone? What design and operating features prevent this?
• Is the overfire (secondary) air system designed with adequate
capacity to achieve the proper penetration and coverage to ensure
good mixing? Do variations in operating conditions (e.g. low
load) result in changes to overfire air that cause the system to
lose penetration and coverage?
« Is auxiliary fuel firing capacity available for use during start-
up, shutdown and off spec (low temperature, high CO) operating
conditions?
» Are combustor/boiler exhaust gas temperatures sufficiently low to
minimize the potential for CDD/CDF formation in f 1 us gas cleaning
equipment?
• Is the unit operated with an acceptable excess air range that is
sufficiently high to provide adequate oxygen to prevent fuel-rich
conditions, yet low enough to prevent quenching of the combustion
reactions?
• Are design and operating conditions adequate to prevent
operational problems such as excessive corrosion, slagging,
fouling, or poor waste volume reduction?
2-6
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Are combustion control measures in place to ensure that the system
is operated within the design envelope?
Retrofit approaches were developed for the models where design.
operation/control, and/or verification deficiencies were identified. Each
retrofit was site-specific, involving addition or modification of existing
equipment or operating procedures, and in some cases, a virtual redesign and
rebuild of the entire combustor. The recommended approaches were based on
past experiences at existing plants, and in some cases, on engineering
judgment. As each modification was developed, the effects on all other parts
of the combustion system were evaluated to ensure that the various modifica-
tions were compatible, and that retrofits were not likely to result in
operational complications.
The final two steps in the study were to develop cost estimates and
emission reductions for each model plant. Cost development is described in a
separate memorandum.13 The rationale for estimating emission reductions is
provided in the following sections of this report.
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3.0 MODEL PLANT PERFORMANCE ESTIMATES
The following subsections discuss the data and provide the rationale for
establishing the baseline emission values in Table 1-2 and the post-
modification emissions estimates in Table 1-3. The subsections are organized
according to model plant combustion technology. The data used to establish
baseline emissions are compiled from emission tests performed at plants that
comprised the existing MWC population. The emission tests can be categorized
as three distinct types:
1. Compliance tests with sampling performed at the stack, downstream
of flue gas cleaning equipment. In most cases these data were
generated under optimal operating conditions at or near design
steam load. In many cases process data such as temperatures and
airflows were not recorded during testing.
2. Compliance tests with sampling performed concurrently at the inlet
and outlet of the flue gas cleaning equipment. In most cases,
limited process data were recorded, and the combustor operated at
or near design steam load.
3. Parametric tests involving multipoint sampling under a variety of
combustor and/or flue gas cleaning device operating conditions.
Process data are usually well documented in these test reports.
The emissions data used in this analysis are presented both in tabular
and graphical form. The data tables present multiple run averages reported
for each test facility. Data measured in a parametric test are averaged and
presented separately for each parametric operating condition. Combustor
design and operating data are also included in the data summary tables. The
data graphs present the emission levels for each sampling run, along with an
average value for each testing condition.
Test reports that include emissions measured upstream of flue gas
cleaning equipment provide the best data to evaluate combustion conditions.
As a result, emission tests in categories 2 and 3 are the primary focus of
this analysis. In some cases, data measured in the stack also provide
information related to combustion conditions. When these data offer some
3-1
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insight into the combustion conditions experienced during testing, they are
also included in the discussion of baseline emissions.
3.1 Mass Burn Waterwall MWCs
Twenty-four facilities comprise the population of existing mass burn
waterwall MWCs. Facility design and operating data are summarized in Table 3-
1. Individual combustor unit sizes in this group range from 50 to 1050 tpd,
with one to four units per plant site. The oldest existing mass burn
waterwall MWC is located at the Naval Shipyard in Norfolk. VA. This plant
commenced operation in 1967. Four of the existing plants began operating in
the 1970's; the remaining 19 facilities commenced operation in this decade.
The Harrisburg, PA, and Glen Cove, NY, plants burn mixtures of sewage sludge
and municipal solid waste: all other plants generally burn 100 percent MSW.
Eight of the 24 facilities use Martin grates. Six plants are equipped
with Von Roll grates and five with Detroit Stoker grates. Most European
manufacturers (Martin, Von Roll, and others) have American licensees that own
the marketing rights of a technology in the U.S. A more detailed discussion
on individual combustor designs is provided in the MWC Report to Congress.5
Other stoker designs used in the existing population include Riley/Takuma and
Morse Boulger.
Seventeen of the 24 existing facilities are equipped with ESP emission
control systems and seven plants use acid gas controls. Spray dryers are in
place at Jackson, MI; Marion County. OR; Commerce, CA; and Millbury. MA. The
Alexandria. VA MWC is equipped with an in-furnace lime injection system;
Claremont, NH uses in-duct lime injection. With the exception of Millbury and
Alexandria which use ESPs, all of the plants with acid gas controls use fabric
filters for PM control. All seven of these facilities have begun operating in
the last 2 years.
Three model plants were developed to represent groups of conventional
mass burn waterwall MWCs. The model plants are designated large, mid-size,
and small based on individual unit capacities. Large plants include
facilities with unit capacities greater than 600 tpd (545 Mg/day); mid-size
plants have unit capacities between 200 and 600 tpd (182 and 545 Mg/day);
small plants have unit capacities less than 200 tpd (182 Mg/day).
3-2
-------
TABLE 3-1. EXISTING MASS BURN WATERWALL COMBUSTORS
PLANT LOCATION
Saugus, MA
Pinellas County, FL
Westchester County, NY
Baltimore, MD
North Andover, MA
Millbury, MA
Bridgeport, CT
Chicago, IL (NW)
Harrisburg, PA
Nashville, TN
Tulsa. OK
Marion County, OR
Hillsborough County, FL
Commerce, CA
Alexandria, VA
Norfolk Naval Sta. , VA
Hampton, VA
Harrisonburg, VA
Glen Cove, NY
New Hanover County, NC
Jackson County, MI
Key West, FL
Olmstead County, MN
Clarmont, NH
MANUFACTURER
STOKER/BOILER
Von Roll/
Dominion Bridge
Marti n/Ri 1 ey
Von Roll/B&W
Von Roll/B&W
Martin/Riley
Von Roll/B&W
Von Roll/B&W
Martin/IBW
Martin/IBW
Detroit Stoker/
B&W
Martin/Zurn
Marti n/Zurn
Martin/Riley
Detroit Stoker/
Foster Wheeler
Marti n/Keel er
Dorr-01 i ver
Detroit Stoker/
Foster Wheeler
Detroit Stoker/
Keeler
Morris Boulger/
Zurn
Morris Boulger/
Zurn
Detroit Stoker/
Keel er
Ri 1 ey/Takuma
Morse Boulger/
Zurn
Riley/Takuma
Von Roll
# OF
UNITS
2
3
3
3
2
2
3
4
2
2
1
2
2
3
I
2
2
2
2
2
2
2
2
2
2
INDIVIDUAL
UNIT SIZE
tpd Mg/day
750 682
1050 954
750 682
750 682
750 682
750 682
750 682
400 364
360 327
360 327
400 364
375 341
275 250
400 364
350 318
325 295
180 164
100 91
50 45
125 114
100 91
100 91
75 68
100 91
100 91
YEAR OF
START-UP
1975
1983
1984
1985
1985
1988
1988
1970
1973
1974
1986
1986
1986
1987
1987
1987
1967
1980
1982
1983
1984
1987
1987
1988
1987
APCD
ESP
ESP
ESP
ESP
ESP
SO/ESP
SD/FF
ESP
ESP
ESP
ESP
ESP
SD/FF
ESP
SD/FF
i nfurnace
lime inj/
ESP
ESP
ESP
ESP
ESP
ESP
SD/FF
ESP
ESP
duct lime
inj/FF
ESP INLET
TEMPERATURE
op oC
450 232
500 260
455 235
400 204
500 260
-
-
428 220
500 260
500 260
450 232
375-505 191-263
-
375-505 191-263
-
375-505 191-263
690 366
425 21£
550 288
560 293
425 218
-
450 232
425 218
-
-------
3.1.1 Large Mass Burn Waterwall MWCs
Seven MWCs are included in this subcategory of existing mass burn
waterwall population. All seven plants are Wheelabrator facilities. Although
the new Wheelabrator designs all use Von Roll grate technology, two of the
existing plants (North Andover and Pinellas County) have Martin grates. The
available emissions data for each of the facilities are summarized in Table 3-
2, along with a summary of combustor design and operating practices.
Additional discussion regarding emissions data and system design and operation
is provided for each facility below. Combustor operating conditions are
presented as reported during the actual testing period, or as reported by
facilities in response to information questionnaires.
3.1.1.1 Millbury. Massachusetts
Wheelabrator Environmental Systems is the U.S. licensee of Von Roll
technology. One of the newest Wheelabrator plants in operation is the
Millbury, MA Resource Recovery Facility, which includes two 750 tpd (682
Mg/day) combustors. Each unit is equipped with a spray dryer and an ESP. The
facility began operating in 1987 and underwent compliance testing in early
1988. In addition to performing stack testing for compliance purposes,
emissions were measured at the spray dryer inlet location. Five CDD/CDF
emission samples were gathered at the spray dryer inlet location at Unit #2,
and average emissions were 170 ng/dscm CDD/CDF. 14 Individual runs ranged from
140 to 210 ng/dscm. Average CO emissions were 38 ppmv (4-hour average) during
the five test runs. The average gas temperature at the inlet sampling
location ranged from 429 to 442°F (221 to 228°C) during the five runs.
An assessment of the combustor design at Millbury indicates that the
majority of design elements are in place to provide good combustion. Furnace
temperatures are measured at the inlet and outlet of the superheater. The
thermocouple at the superheater inlet location is approximately 35 feet (10.7
m) above the last point of overfire air injection, and a typical operating
temperature at this location is 1500°F (816°C). Millbury has five
individually controllable underfire air plenums along the length of the
reciprocating grates. One design feature at Millbury that differs from older
Von Roll systems is the overfire air capacity. The overfire air system has
the capacity to supply 60 percent of total combustion air. The Millbury units
operate with 40-50 percent of total air supplied as overfire air. Many Von
3-4
-------
TABLE 3-2. LARGE MASS BURN WATERWALL MWCS
PAGE 1 OF 3
PERFORMANCE ASSESSMENT
FACILITY
NUMBER OF UNITS - Flue gas
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requi rement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
cleaning equipment (FGC)
GOOD COMBUSTION
PRACTICE RFCOMMENDATIONS
1800°F (982°C) mean
At least 4 plenums along
grate length
40% total air
Complete penetration/
coverage
As required to achieve
temperature limits
during start-up
<450°F (232°C) at. PM
control device inlet
6-12% 02 (dry)
80-110% design load
Penetration and coverage
of furnace cross section
Auxiliary fuel to design
temperature
High CO, low temp;
start-up/shutdown
Monitor
Monitor «50 ppm at 7% 02)
Monitor
Monitor
Monitor
Hi 11 bi^y, MA
2 - SO/tSP
750 (682)
170
38
NA
59.2
FACILITY DESIGN
AND OPERATING CONDITQON.S
1500°F (8IG°C; at
superheater i';\let
5 plenums * (r »;
grate length
At least 60% total air
3 rows (/ front. 1
Gas - 405. i ia>j
435°F
10.2% 02
Baseloadec! - J00% ±3%;
66% minimum
40-50% total air
Gas - 1500C'F (8].6CC) at
superheater inlet
Start-up/shutdown
Yes
Yes
Superheater inlet/
outlet
OFA, UFA pressures
Yes
3-5
-------
TABLE 3-2. LARGE MASS BURN WATE.RWALL MlvCS - PERFORMANCE ASSESSMENT
PAGE 2 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EHISS IMS
CDD/CDF (ng/dscmj
CO (ppmv)
COMBUSTION PARAMETERS
DESIGN
Temperature at fully
mixed height.
Underfire air
Overfire air capacity
(not an operating
requi rement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Pi ne? las Coiir-Ly, FL
3 - ESP
1050 (954)
69
4
2250
132
fAf.ll ITY DESIGN
IA] J Hfi. .CONDI 1.1 QMS,.
Wcstc^octer County, v.JF A ps'tiiures
Exit gas temperature
-------
TABLE 3-2. LARGE MASS BURN WATERWALL MWCS - PERFORMANCE ASSESSMENT
PAGE 3 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
North Andover, MA
2 - ESP
750 (682)
246
43
2230
362
FACILITY DESIGN
AND OPERATING CONDITIONS
Saugus. MA
2 - ESP
750 (682)
490
40
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requi rement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
NA
5 plenums along
grate length
At least 40% total air
2 rows
None
500°F (260°C)
11% 02
Baseloaded - 100%
Minimum load - 52%
40% of total air
No auxiliary fuel
None
Yes
Yes
5 points in boiler
OFA. UFA pressures
Yes
NA
6 plenums along
grate length
At least 40% total air
4 rows
None
450°F (232°C)
8-10% 02
Baseloaded - 100%
Minimum load - 50%
30-40% total air
No auxiliary fuel
None
Yes
No
Superheater inlet.
economizer outlet
OFA/OFA flows
Yes
3-7
-------
Roll facilities constructed prior to Millbury operate with 30-40 percent of
total airflow as overfire.
The majority of operation/control and verification elements representing
good combustion practice are also in place at Millbury. The units typically
operate at full capacity generating electricity, so low load operation is
infrequent. All the recommended monitoring procedures are in place at
Millbury.
3.1.1.2 Pinellas County. Florida
The Pinellas County MWC consists of three 1050 tpd (954 Mg/day)
combustors. with Martin stokers and three-field ESPs. The #1 and #2 units
started up in 1983, and #3 commenced operation in 1986. Six ESP inlet/outlet
CDD/CDF emission tests were conducted at Unit #3 in February and March 1987.
Average inlet emissions were 69 ng/dscm and average CDD/CDF emissions in the
stack were 132 ng/dscm.9 Average flue gas temperatures at the ESP inlet
location ranged from 523 to 553°F (273 to 289°C). Average PM and CO values
measured at the ESP inlet were 0.98 gr/dscf (225 mg/dscm) and 4 ppmv.
respectively. The CO emissions were measured concurrently with CDD/CDF
testing, which was 3 hours' duration. Boiler #3 operated between 88 and 91
rated capacity during the six test runs, and 02 concentrations varied from 6.9
to 7.7 percent (wet basis). Average furnace temperatures reported during
testing varied from 1824°F (996°C) to 1923°F (1051°C). measured in the upper
furnace. Underfire and overfire air plenum pressures were recorded and were
fairly consistent during all of the runs. Actual airflow splits are not
available.
The design of the Pinellas County plant meets the majority of criteria
required for good combustion. However, Pinellas County does not have
auxiliary fuel burners. In addition, the normal ESP operating temperature is
approximately 500°F (260°C). The ESP temperature is assumed to have
contributed to the increased CDD/CDF concentrations measured at the ESP outlet
location. Based on the emission test results (low organics and CO levels), it
is concluded that the unit achieves good mixing. The three units at Pinellas
County are operated on a manual combustion control scheme, with the exception
that steam production rates are automatically controlled. The majority of
mass burn waterwall MWCs are equipped with fully automatic combustion
controls. A manual control scheme may allow greater potential for combustion
3-8
-------
upsets to occur. With the exception that the units do not monitor CO
continuously. Pinellas County has all of the verification measures in place to
ensure good combustion practices are maintained.
3.1.1.3 Uestchester County. New York
The Westchester County. NY, plant includes three 750 tpd (682 Mg/day)
Von Roll combustors. each equipped with a three-field ESP. The plant wa~>
tested for CDD/CDF as part of a two-phase program. Phase I, completed in
1985. involved only three sampling runs performed in the stack downstream of
the ESP. The average CDD/CDF concentration was 102 ng/dscm.15 Histograms are
presented in the test report showing CO levels and superheater gas
temperatures measured during run #2. The CO data vary between 10 and 20 ppmv
during the 4-hour testing period. The superheater gas temperature was
approximately 1100°F (593°C). There are no other process data available in
the report.
Phase II of the testing program at Westchester was a parametric testing
effort designed to examine the effects of combustor operating conditions on
MWC emission levels. Samples of CDD/CDF were gathered in flue gases at three
locations in the system (superheater exit, ESP inlet, and ESP outlet) during
the following test conditions:
o end of campaign (prior to scheduled maintenance)
o beginning of campaign (after scheduled maintenance)
o high load (115 percent of design)
o low load (85 percent of design)
o cold start-up (with gas preheat)
The emission results from the parametric test are summarized in Table 3
3.12 The CDD/CDF results presented for each sampling condition are three-run
averages. The CDD/CDF emissions are relatively low at the superheater exit
during all test conditions. As the gas temperatures were reduced between the
superheater exit location and the ESP inlet, average CDD/CDF concentrations-
increased. This trend occurred during all conditions except low load, where
an 11 percent reduction in average CDD/CDF concentration was measured.
Reductions in CDD/CDF concentration were measured between the ESP inlet
and outlet during all operating conditions. The reduction in CDD/CDF
3-9
-------
TABLE 3-3. DATA SUMMARY - WfSTCHESTL R O^HTY PARAMETRIC TEST*
CDD/CDF
End
Beginning
High
Low
££
End
Begi nning
High
Low
PM
End
Beginning
High
Low
Gas Temperature
End
Begi nni ng
High
Low
SUPERHEATER EXIT
ng/dscm
184
122
301
255
ppmv
16 (2 runs)
31
35
38
gr/dscf (mg/dscm)
1.32 (3040)
1.66 (3820)
1.61 (3700
1.28 (2940)
°F (°C)
1180 (638)
1119 (604)
1139 (615)
1034 (557)
ESP INLET
ng/dscm
619
478
438
228
ppmv
7
24 (1 run)
35
22
gr/dscf (mg/dscm)
1.86 (4280)
1.35 (3110)
1.89 (4350)
0.89 (2050)
°F (°C)
471 (244)
445 (229)
454 (234)
437 (225)
ESP OUTLET
rig/dsun
179
262
126
148
ppmv
7
24 (.1 run)
35
22
gr/dscf (mg/dscm)
.0228 (53.4)
.0137 (31.5)
.0133 (30.6)
.0142 (32.7)
°F (°C)
445 (229)
424 (218)
433 (223)
415 (213)
*Three run average unless otherwise noted
3-10
-------
concentration ranged from 35 percent during the low load condition to 71
percent during the end of campaign and high load conditions. The CDD/CDF
reductions do not appear to be solely the resuK of TSP operating temperature.
The two highest CDD/CDF reductions occurred during operating conditions where
ESP temperatures were highest (end of campaign and high load). The CDD/CDF
formation reactions occur while CO levels remain relatively low. These data
support the conclusions concerning the CDD/CDF and CO relationship. High CO
is a general indicator of high CDD/CDF; however, low CO can be present with
variable CDD/CDF emissions.
The Westchester facility meets the majority of recommendations for good
combustion practice. The plant generates electricity and operates at full
load whenever possible.
3.1.1.4 North Andover. Massachusetts
The available emissions data from North Andover consist of three CDD/CDF
sampling runs at the ESP inlet and five runs in the stack. The plant
comprises two Martin units, each rated at 750 tpd (682 Mg/day). The ESP inlet
sampling was performed by EPA in 1986 in conjunction with State compliance
testing. The average inlet CDD/CDF concentrations were 246 ng/dscm.8 Three
simultaneous stack test runs averaged 344 ng/dscm. The ESP inlet temperature
during testing varied from 580 to 591°F (304 to 311°C) with an average value
of 585°F. Two additional stack test runs are available, but the corresponding
inlet runs were invalidated due to sampling or process problems experienced in
the field. The average stack emission rate was 382 ng/dscm using all five
runs.
Average CO emissions were also relatively constant (average value 43
ppmv). Review of the CO histograms indicated no significant spikes during the
three ESP inlet runs. Particulate emissions were not measured at the ESP
inlet during CDD/CDF testing runs. Sampling performed separately from the
CDD/CDF emission runs indicated an average ESP inlet PM grain loading of 0.97
gr/dscf (2230 mg/dscm).
Some process data were gathered during the emissions test, including
steam load, airflows, and temperatures. The units operated near 95 percent
design steam load at 90-100 percent excess air during the CDD/CDF tests. With
the exception of the ESP inlet gas temperature and the lack of auxiliary fuel
3-11
-------
supplies, the North Andover facility meets recommendations for good combustion
practice.
3.1.1.5 Sauqus. Massachusetts
Stack compliance testing was performed in 1986 at the Saugus. MA
facility, the oldest existing Wheelabrator plant. The plant began operating
in 1975. Seven sampling runs were performed in June 1986 and three runs were
performed in August 1986. Both tests were completed at normal operating
conditions. Emissions ranged from 486 to 897 ng/dscm in June and 425 to 928
ng/dscm in August.16 The highest and lowest three-run averages from the June
test were 570 ng/dscm and 773 ng/dscm, respectively. Average emissions in the
August test were 490 ng/dscm. The combustor was operated between 81 and 84
percent of full steam load with excess air levels ranging from 67 to 96
percent. Overfire air comprised approximately 40-45 percent of total airflow.
The average ESP operating temperature during testing was approximately 550°F
(288°C). As a result, it is judged that some of the CDD/CDF in the stack
resulted from formation that occurred in the ESP. Average CO emissions during
the test were 41 ppmv (4-hour average).
Information obtained from a Section 114 questionnaire response indicates
that the ESP operating temperatures have been lowered by approximately 100°F
(38°C) at Saugus. This modification is expected to reduce CDD/CDF stack
emissions by minimizing the potential for catalytic formation reactions to
occur in the ESP. With the exception of lacking an auxiliary fuel source and
CO monitors, the Saugus facility meets the recommended good combustion
practices.
3.1.1.6 Baseline Emission Estimates
The available unabated CDD/CDF emissions data from existing MWCs
represented by the large mass burn waterwall model plant are plotted in Figure
3-1. The data include measured emissions from four existing facilities (Mill-
bury, North Andover, Pinellas County, and Westchester County). Individual
sampling runs and multiple averages are included for each facility. Data
generated during different parametric operating conditions are presented
separately for the Westchester MWC.
3-12
-------
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o
o
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w
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3
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3-13
-------
Three of the plants achieved CDD/CDF emissions less than 250 ng/dscm.
All three of these tests were compliance tests. The Westchester facility
exhibited more variable ESP inlet emissions, with averages ranging from 228 to
618 ng/dscm. All of the parametric operating conditions experienced during
the Westchester sampling program may be considered "normal operation" with the
possible exception of the high load condition, where steam flows were 115
percent of design. Therefore, the range of emissions measured during the
parametric test at Westchester reflects the variation in CDD/CDF that can be
expected during normal operating conditions in an MWC. The three compliance
tests do not show these variations. Baseline (unabated) CDD/CDF emissions of
500 ng/dscm were established for the large mass burn waterwall model plant.
Figure 3-2 presents a graphical summary of available CDD/CDF data
measured downstream of ESP controls. The average data from the Saugus
facility (6/86 test) exceeds the baseline (500 ng/dscm). Based on the
operating temperature of the ESP during the test, it is judged that the
CDD/CDF emissions may have increased from ESP inlet levels as a result of
formation in the ESP. Although the amount of CDD/CDF formation cannot be
quantified based on the available data, it is assumed that the inlet CDD/CDF
emissions at Saugus are below the established baseline.
There are seven existing facilities represented by the large mass burn
waterwall model plant. CDD/CDF emissions data are available for all plants
except Baltimore, MD and Bridgeport, CT. The Baltimore plant is nearly
identical in design to the Westchester facility, and the Bridgeport and
Millbury combustors also use the same design. Therefore, it is judged that
the emissions performance of the two plants is similar, and all plants in this
subcategory are expected to be able to achieve the baseline CDD/CDF emissions.
The available CO data from conventional mass burn waterwall MWCs of all
sizes indicates that the majority of facilities can achieve 50 ppmv CO on a 4-
hour average. Thus, the baseline emission level was established at 50 ppmv.
Inlet particulate emissions will vary according to boiler design, air
distribution, and waste characteristics. For example, facilities that operate
with high underfire/overfire air ratios or relatively high excess air levels
may entrain greater quantities of PM and have higher uncontrolled emissions.
Boilers with multiple passes that change the direction of flue gas flow in the
convective section may remove greater quantities of entrained PM prior to
entering flue gas cleaning equipment. Lastly, the physical properties of
3-14
-------
c
z>
CC
T3
Q
CD
"35
CO
8
o
8
00
8
*
i
8
CM
M0~)
O
(0
PU3
SB||9U!d
(dS3)
JSAOpUV "N
(dS3) >peis
(98/8) snones
(dS3) >P*»S
(98/9) snGneg
(dS3/QS)
O
*« I
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Q)
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3-15
-------
waste being fed to a unit may impact the amount of PM that becomes entrained.
The available data for the units discussed above ranges from 0.97 gr/dscf
(2230 mg/dscm) at North Andover to 1.50 gr/dscf (3520 mg/dscm) at Westchester.
Because all of the data are less than 2 gr/dscf (4600 mg/dscm), this value was
selected as the baseline.
3.1.1.7 Emission Reductions Resulting from Combustion Modifications
The performance of the model plant representing large mass burn
waterwall MWCs was judged to achieve good combustion. The only recommended
modification was the addition of continuous CO monitors to verify good mixing
and stable combustion conditions.
3.1.2 Mid-Size Mass Burn Waterwall MWCs
Eight existing MWCs are included in this subcategory of the mass burn
waterwall population. Six of the facilities use Martin grates and two use
Detroit Stoker grates. The available emissions data for each of the
facilities are summarized in Table 3-4. along with a summary of combustor
design and operating practices. Additional discussion regarding emissions
data and system design and operation is provided for each facility below.
3.1.2.1 Commerce. California
The Commerce. CA. MWC consists of one 350 tpd (318 Mg/day) unit with
Detroit Stoker grates and a Foster Wheeler boiler. The unit is equipped with
a spray dryer/fabric filter. Commerce was also the first MWC in the U.S. to
use thermal de-NOx controls. The facility underwent an emissions test in 1987
for compliance purposes. The CDD/CDF emissions data were measured according
to the draft California Air Resources Board (CARB) Modified Method 5 (semi-
VOST) protocol. Two test runs were conducted at the stack while burning the
largely commercial waste normally received at the facility. A third test run
was conducted with simultaneous measurement at the boiler exit and stack while
burning a residential refuse brought in from Long Beach. California
specifically for the test. Steam load was reduced from full load to 80
percent of capacity during the inlet/outlet sampling. During the one test run
that was conducted at the spray dryer inlet. 27 ng/dscm CDD/CDF was measured.
Inlet PM and CO emissions were 1.56 gr/dscf (3590 mg/dscm) and 16 ppmv (1-hour
average), respectively.1?
3-16
-------
TABLE 3-4. MIDSIZE MASS BURN WATERWALL MWCS - PERFORMANCE ASSESSMENT
PAGE 1 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
GOOD COMBUSTION
PRACTICE RECOMMENDATIONS
Commerce, CA
1 - SD/FF
350 (318)
27
4620
1.70
16
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requirement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1800°F (982°C) mean
At least 4 plenums along
grate length
40* total air
Complete penetration/
coverage
As required to achieve
temperature limits
during start-up
<450°F (232°C) at PM
control device inlet
6-12* 02 (dry)
80-110* design load
Penetration and coverage
of furnace cross section
Auxiliary fuel to design
temperature
High CO. low temp:
start-up/shutdown
Monitor
Monitor «50 ppm at 7* 02)
Monitor
Monitor
Monitor
3-17
1750°F (926°C) at
superheater inlet
6 plenums (2 per
grate length)
40% total air
5 rows (2 front.
2 rear. 1 side)
Gas - 100* load
480°F (249°C)
10* 02 ±2*
70-101* design load
20-40* total air
On gas
Start-up/shutdown
Yes
Yes
Yes
OFA, UFA pressures
Yes
-------
TABLE 3-4. MIDSIZE MASS BURN WATERWALL MWCS - PERFORMANCE ASSESSMENT
PAGE 2 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Marion County, OR
2 - SD/FF
275 (250)
43
18
205
1.39
FACILITY DESIGN
AND OPERATING CONDITIONS
Alexandria, VA
3 - FI/ESP
375 (341)
53
18
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requirement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1400-1600°F (760-872°C)
at superheater inlet
5 plenums per grate run
At least 40% total air
3 rows
Gas - 30% load
392°F (200°C)
7-12% 02
75-105* design load
20-403; total air
Gas to 1800°F (982°C)
Start-up/shutdown
Yes
No
Middle and top of
furnace
OFA, UFA pressures
Yes
1400-1600°F (760-872°C)
at superheater inlet
5 plenums along grate
length
At least 40* total air
2 rows
Oil - 25% thermal load
375-505°F (191-263°C)
7-12% 02
80-100% load
20-40% total air
On oil to 1400°F (760°C)
Start-up/shutdown
Yes
Yes
Furnace exit
(superheater inlet)
OFA. UFA pressures
Yes
3-18
-------
TABLE 3-4. MIDSIZE MASS BURN WATERWALL MWCS - PERFORMANCE ASSESSMENT
PAGE 3 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Tulsa, OK
3 - ESP
375 (341)
Chicago. IL
4 - ESP
400 (364)
36
22
FACILITY DESIGN
AND OPERATING CONDITIONS
254
1-223
FACILITY DESIGN
AND OPERATING CONDITIONS
PESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requirement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1400-1600°F (760-872°C)
at superheater inlet
5 plenums along
grate run
At least 40% total air
NA
None
375-515°F (191-263'C)
7-12% 02
72-100% load
20-40% total air
No auxiliary fuel
None
Yes
Yes
NA
OFA, UFA pressures
Yes
1470°F (799°C) at
convection section inlet
6 plenums along
grate run
At least 26% total air
2 rows
Gas - 100% load
450°F (232°C)
8-10% 02
NA
26% total air
On gas
Start-up
Yes
No
3 locations
OFA. UFA pressures
Yes
3-19
-------
The amount of process data included in the emissions test report is
fairly limited. Steam load varied from 80 to 103 percent of capacity during
the test. The thermal de-NOx system was operational throughout the testing
period except for one test run when the NOX levels were measured without
ammonia injection. This control system demonstrated NOX reduction in excess
of 40 percent. The report contains no information on combustion air operating
levels.
The Commerce facility has all of the design components of good
combustion in place. It is judged that the 1700°F (927°C) superheater inlet
temperatures correspond to a temperature at the fully mixed height which meets
the good combustion recommendations. The operation of the facility is
maintained by a fully automatic control system. The unit generates
electricity, operating at full load whenever possible. All of the
verification measures are in place to monitor continuous performance and
ensure good combustion.
3.1.2.2 Marion County. Oregon
The Marion County. OR MWC consists of two 275 tpd (250 Mg/day) Martin
combustors equipped with spray dryers and fabric filters. The units commenced
operation in 1986. During stack compliance testing in September 1986. EPA
performed three sampling runs at the boiler outlet (spray dryer inlet)
location. Two of the three sampling runs were invalidated, but the results of
the one successful run indicated an inlet CDD/CDF emission rate of 43 ng/dscm.
In addition, inlet particulate emissions were 0.89 gr/dscf (2050 mg/dscm). and
CO emissions were 18 ppmv (4-hour average).18
Process data were recorded during the compliance test at Marion County.
The steam load was 97 percent of design load during CDD/CDF testing. Gas
temperatures measured in the middle of the first furnace pass averaged 1741°F
(949°C). and the average economizer outlet temperature was 392°F (200°C).
Average exhaust gas oxygen concentrations were 9.5 percent, and the estimated
overfire/underfire air ratio was 25/75. The Marion County units are equipped
with auxiliary fuel burners that can provide 30 percent of thermal load. The
units do not have continuous CO monitors.
3-20
-------
EPA gathered an additional 14 unabated CDD/CDF samples at Marion County
in February 1987. During all of the sampling runs, the boiler was operated at
normal, full load conditions. Analysis was completed on seven of the runs.
Four of the seven samples had acceptable spike recoveries and were full
traverse samples. Three of the seven runs were either single point samples or
were invalidated due to poor recoveries. The CDD/CDF values from the valid
test runs ranged from 56 to 116 ng/dscm, with an average value of 99
ng/dscm.i9
3.1.2.3 Alexandria. Virginia
The Alexandria, VA facility, which began operating in 1987, consists of
three 375 tpd (341 Mg/day) units. The system design includes in-furnace lime
injection for acid gas control, and ESPs for PM control. Results of
compliance testing performed at Unit #1 in December 1987 indicated a three-run
average of 53 ng/dscm CDD/CDF and 18 ppmv of CO (3-hour average) in the
stack.20 Limited process data are included in the compliance test report.
The boiler reportedly operated between 98 and 99 percent design steam load
during the three runs, and average Oz concentrations were 9.5 percent. The
furnace temperature was measured at an unspecified furnace exit location with
an unshielded thermocouple. The average temperature during the three runs was
1651°F (899°C), 1664°F (907°C>, and 1642°F (894°C). The test report authors
state that the measurement method "should be regarded as being relatively
accurate; i.e.. lower than the actual temperature by approximately 150-200°F.
but precise." The average stack temperature was reported to be 342°F (172°C)
while sampling, so it is judged that the ESP temperature was below 450°F
(232°C). Although the existing data base does not provide a basis for
estimating the effect of dry lime furnace injection on CDD/CDF, the emission
levels are typical of those measured at other Martin systems, that do not use
acid gas controls.
The facility is judged to satisfy the majority of criteria included in
the good combustion practice recommendations. The gas temperatures at the
superheater inlet are reported to vary from 1400°F (760°C) to 1600°F (871°C).
The plant has an auxiliary fuel source (oil), and the firing capacity is 25
percent of boiler load.
3-21
-------
3.1.2.4 Tulsa. Oklahoma
Emissions data from two other facilities using Martin designs were also
used to establish baseline emission factors for the model plant. The first of
these is the Tulsa, OK facility, which is comprised of three 375 tpd (341
Mg/day) combustor units. The facility began operating in 1986. Each of the
units is equipped with an ESP. The ESP inlet gas temperature typically varies
from 375 to 515°F (191 to 268°C). Available emissions data gathered for
compliance purposes indicates average COD/CDF emissions of 36 ng/dscm at the
stack location.21 The flue gas temperature during testing was not included in
the report. Emissions of CO averaged 22 ppmv at Unit #1 and 27 ppmv at Unit
#2. The CO data were gathered separately from the CDD/CDF data, and are
presented as 1-hour averages. There are no process data available in the test
report to use in evaluating the combustor operating conditions. With the
exception that Tulsa does not have auxiliary fuel, all of the requirements of
good combustion are assumed to be achieved at this facility.
3.1.2.5 Chicago Northwest. Illinois
The Chicago Northwest MWC is comprised of four units with individual
capacities of 400 tpd (364 Mg/day). Each of the units is equipped with Martin
stokers and ESP controls. Emissions of CDD/CDF and other organics (total
organic chloride, PAH, PCB) were measured in the stack of Unit #2 between
April 30 and May 23. 1980. The plant was operated at normal steady state
conditions to the greatest extent possible during the tests. The average
CDD/CDF emissions in the stack were reported to be 254 ng/dscm.22 Daily
average CO emissions from Unit #2 varied from 1 ppmv to 223 ppmv during the 11
days when organics sampling was performed. The average flue gas temperature
in the ESP was 500°F (260°C).
3.1.2.6 Baseline Emission Estimates
The available CDD/CDF emissions data from existing MWCs represented by
the mid-size mass burn waterwall model plant are plotted in Figure 3-3. The
data include APCD inlet emissions from two plants (Commerce and Marion County)
and stack emissions from three facilities (Alexandria. Tulsa, and Chicago NW).
With the exception of the Chicago NW data set, all the measured emissions are
less than 200 ng/dscm. Although inlet CDD/CDF data are not available from
3-22
-------
C
tr
"2
C
3
m
<0
<0
co
2
1
*?
to
O)
O
o
CM
O
o
(ZQ %L »e Luosp/6u)
3-23
-------
Chicago NW, it is assumed that the emissions are below 200 ng/dscm, and that
the the higher stack concentrations resulted from formation in the ESP.
Therefore, all of the plants are assumed to achieve emissions less than 200
ng/dscm, and this value is selected as a baseline APCD inlet emission level.
Baseline inlet CO and PM emissions were established at 50 ppmv and 2 gr/dscf
(4600 mg/dscm). respectively, using the available data for facilities
represented by the model plant. It is assumed that all facilities in the
subcategory can achieve the baseline emission levels.
3.1.2.7 Emission Reductions Resulting from Combustion Modifications
The mid-size mass burn waterwall model plant is assumed to satisfy the
design and operating criteria in the good combustion practice recommendations.
The only recommended modification for the model was the addition of continuous
CO monitors to verify good mixing and stable operation.
3.1.3 Small Mass Burn Waterwall MWCs
The existing population of small mass burn waterwall MWCs comprises nine
facilities. The nine plants use four separate grate designs, with no single
manufacturer dominating this segment of the market. Only two of the plants
(Hampton, VA, and Claremont, NH) have reported CDD/CDF data.
3.1.3.1 Hampton. Virginia
The Hampton facility has been tested for CDD/CDF on five separate
occasions. Table 3-5 presents an historical emissions summary for the
facility.23-24 In each case, testing was performed in the stack downstream of
the ESP. Process data measured during the 1984 test indicated that during
normal operating conditions, excess Oz levels and furnace temperatures were
highly variable.25 In addition, typical ESP operating temperatures were in
the range of 550 to 600°F (288 to 316°C). A summary of design and operating
parameters is presented for the facility in Table 3-6 for the period during
which these tests were performed.
Following the completion of the 1984 emissions test, the plant operators
initiated a retrofit program to modify the design and operation of the
units.26 This was not only due to concerns related to emissions, but also due
to the need for corrective action to address operating problems that were
3-24
-------
TABLE 3-5. CDD/CDF EMISSIONS HISTORY
HAMPTON, VA MWC
YEAR
1981
1982
1983
1984
1986
CDD/CDF
(ng/dscm)
25,017
663*
10.423
22,325
155
NUMBER OF
SAMPLING RUNS
3
3
5
3
3
CO
(ppmv)
1082
209
24
*1982 data include tetra-CDD/CDF homologues only
3-25
-------
TABLE 3-6. SMALL MASS BURN WATERWALL MWCS - PERFORMANCE ASSESSMENT
PAGE 1 OF 2
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Hampton, VA
(pre-retrofit)
2 - ESP
100 (91)
GOOD COMBUSTION
PRACTICE RECOMMENDATIONS
22.325 (1984)
1082 (1983)
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requirement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1800°F (982°C) mean
At least 4 plenums along
grate length
40X total air
Complete penetration/
coverage
As requried to achieve
temperature limits
during start-up
<450°F (232°C) at PM
control device inlet
6-12% 02 (dry)
80-1102; design load
Penetration and coverage
of furnace cross section
Auxiliary fuel to
design temperature
High CO, low temp:
start-up/shutdown
Monitor
Monitor «50 ppm at 7% 02)
Monitor
Monitor
Monitor
3-26
1300-1600°F (704-871°C)
in upper furnace
3 plenums along
grate length
<20% total air
No
None
550°F (288°C)
2-10%
NA
Not achieved
No auxiliary fuel
None
Yes
No
Yes
NA
Yes
-------
TABLE 3-6. SMALL MASS BURN WATERWALL MWCS - PERFORMANCE ASSESSMENT
PAGE 2 OF 2
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDO/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Hampton, VA
(post-retrofit)
2 - ESP
100 (91)
Claremont. NH
2 - DI/FF
100 (91)
155
24
FACILITY DESIGN
AND OPERATING CONDITIONS
37
50-70
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
(not an operating
requi rement)
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1600°F (871°C) at first
convective section inlet
3 plenums along
grate length
45% total air
2 rows each on front
and rear wal1s
None
425°F (218°C)
7% 02
50-100% design load
Achieved - assumed based
on CO and CDD/CDF
No auxiliary fuel
None
Yes
Yes
Yes
Yes, OFA/UFA
NA
1800-2000°F (982-1093°C)
in upper furnace
4 plenums along
grate length
40-50% total air
2 rows (1 front, 1 rear)
Gas - 50% load
500°F (260°C)
9-12% (wet)
60-100%
40-50% total air
Gas
Start-up/shutdown
Yes
Yes
Yes
OFA/UFA pressures
Yes
3-27
-------
plaguing the boilers. The original cast iron grate bars were replaced with
high alloy chrome-nickel grates and the life of the grates was extended from 4-
6 months to 2-3 years. High alloy blocks were retrofitted on the lower side
walls of the furnace, replacing existing silicon carbide refractory, and
resulting in improved heat transfer and reduced clinker formation. Steam coil
air preheaters were also added to the units for operation during periods of
wet waste firing.
The major improvements that were made to reduce emissions were primarily
related to combustion airflows and distributions. First, it was determined
that the forced draft fan supplying the overfire air was providing less than
half its design capacity. The fan blades were modified and the discharge duct
size was increased, making the flow more aerodynamic. These modifications
restored the overfire air supply to its original design capacity (45 percent
of total air). The plant personnel also realized that mixing was not
optimized, so they began to evaluate the size and orientation of the overfire
air nozzles. There are four rows of overfire air nozzles (two rows on each of
the front and rear walls). The orientation of the lower two rows was changed
based on visual observations made in the furnace. The angle of the front row
was raised from -45° (from the horizontal) to -22.5°. The angle of the rear
wall nozzle row was changed from -20° (from the horizontal) to 0° (hori-
zontal). Now the overfire air jets converge at a point approximately 5 feet
(1.5 meters) above the grate rather than directly on the grate.
Modifications were also made to the operation and combustion control
system. The grate speeds, which were automatically controlled, were switched
to manual, which allowed the speed to be varied from 0 to 80 percent rather
than 40 to 80 percent. This provided more flexibility to deal with varying
waste characteristics (particularly wet waste), and resulted in improved
burnout. A 15 point CO profile was performed at the economizer outlet, and it
was determined that CO was highest when active burning occurred on the burning
grate. When the bed length was extended to provide active burning on the
finishing grate, there were problems with solids burnout. An oxygen trim loop
was installed which provides automatic control of the underfire air
distribution based on the 02 content of the flue gases. The control loop
balances the distribution between the two grates, providing good waste burnout
and maintaining 7-9 percent QZ in exhaust gases.
3-28
-------
Finally, the existing economizer was replaced with new tube banks which
drop the flue gas temperature to 425°F (218°C) at the ESP inlet. Previously
the ESP operated at approximately 550°F (288°C). where the potential for
CDD/CDF formation was relatively high. Installation of the new economizer has
reduced total fuel consumption on an hourly basis, but this has been offset by
increased system availability, so that overall steam output and waste
throughput has actually increased.
The most recent emission test performed at Hampton resulted in stack
emissions of 155 ng/dscm CDD/CDF and CO levels of 24 ppmv.24 The design and
operating characteristics of the facility following the combustion retrofit
are presented in Table 3-6. The design and operating improvements represent a
major step toward attainment of good combustion practices. This is well
documented by the resulting emission levels, which are presented in Tables 3-5
and 3-6.
3.1.3.2 Claremont. New Hampshire
The second set of CDD/CDF data available from a small mass burn
waterwall MWC was measured in 1987 at Claremont. NH. Claremont comprises two
100 tpd (91 Mg/day) units with Von Roll grates. Acid gas control is achieved
by in-duct lime injection downstream of the boiler; PM control is achieved by
a baghouse. Dilution air is added to the duct prior to the lime injection
point in order to provide flue gas temperature reduction. Both units were
tested for CDD/CDF as part of a compliance demonstration test. The average
emissions (four-run average) in the stack were 38 ng/dscir for Unit #1 and 37
ng/dscm for Unit #2.27 it is not possible to estimate combustor emissions of
CDD/CDF since the effects of the dry injection/fabric filter controls in
reducing emission levels of CDD/CDF are unknown. Temperatures in the stack
were 418°F (214°C) and 445°F (229°C). Facility design and operating
information is presented in Table 3-6.
3.1.3.3 Baseline Emission Estimates
Very limited measured data are available from small mass burn waterwall
MWCs. This group of combustors is not dominated by a single system
manufacturer such as Von Roll or Martin in the large and mid-size populations.
Based on a review of facility design and operating practices, it was
determined that there are small mass burn waterwall combustors that satisfy
3-29
-------
the good combustion criteria, and others that lack some necessary design and
operating features associated with good combustion. As an example, one of the
facilities visited in the Retrofit Study was the New Hanover County. NC MWC.
During the site visit, the plant was reportedly experiencing problems related
to erosion and corrosion of heat transfer surfaces similar to those
experienced at the Hampton plant.1 While there are no measured CDD/CDF data
from the New Hanover County units, there was reason to anticipate problems
similar to those at Hampton related to emissions performance. In fact, a
feasibility study was under way to examine potential combustion retrofit
options at the plant. The problems experienced at Hampton may not be unique
to that facility in the small mass burn waterwall population. However, there
are other plants that meet the recommendations for good combustion, and
emissions from these facilities are expected to be relatively low. Therefore.
the model plant represents only a portion of the facilities in the existing
population. It is not intended to represent those plants in the existing
population that have good combustion practices in place.
There were no data from existing U.S. plants to use in estimating a
baseline except for those measured at Hampton prior to the combustion
retrofit. An engineering judgment was made that CDD/CDF emission levels as
high as the pre-retrofit Hampton data were not representative for the group of
facilities represented by the model. Therefore, these data were not used to
establish baseline emission levels.
A data set gathered at a mass burn waterwall MWC in Quebec City, Quebec
was used to establish baseline emissions for the model plant. The Quebec City
MWC comprises four 250 tpd (225 Mg/day) combustors using Von Roll grates and
Dominion Bridge boilers. Emissions control is achieved by two-field ESPs.
The plant was the host site for a combustion evaluation and retrofit program
performed by Environment Canada in 1985-86.28 Prior to the combustion
evaluation program. Environment Canada also investigated the performance of a
pilot-scale acid gas scrubbing system and a baghouse on the control of
multipollutant emissions at the Quebec facility.29 The pilot-scale test
included measurement of APCD inlet CDD/CDF emissions in a slipstream drawn
from the ESP inlet duct at the #3 unit. The slipstream arrangement was used
to direct a flow of combustion gases into a Flakt pilot scale scrubbing system
that included a quench reactor, a dry reactor, and a fabric filter. The
average CDD/CDF emissions measured during 12 sampling runs at the pilot system
3-30
-------
inlet were 1840 ng/dscm. and average CO emissions were 370 ppmv. A graphical
presentation of the CDD/CDF emissions is shown in Figure 3-4.
The design and operating features of the small mass burn waterwall model
plant were assumed to be similar in many respects to those of the Quebec City
units prior to the combustion retrofit program. Therefore, the inlet data
measured at the Quebec City facility were used to establish baseline emission
levels for the model plant. 2000 ng/dscm CDD/CDF and 400 ppmv CO (4-hour
average). An average PM emission rate of 2 gr/dscf (4600 dscm) was selected
for the model plant.
3.1.3.4 Emission Reductions Resulting from Combustion Modifications
The required modifications for the small mass burn waterwall model plant
included flow modeling studies and a redesign of the overfire air nozzle
arrangement, installation of auxiliary fuel burners for start-up and shutdown
operation, installation of CO monitors to verify combustion conditions, and
the addition of an oxygen trim loop to provide automatic adjustment of
underfire air distributions. It was estimated that following these
modifications. CDD/CDF emissions would be reduced to 200 ng/dscm, and CO
emissions would be reduced to 50 ppmv (4-hour average). These emission
reduction estimates were made based on results from combustion retrofit
programs carried out at the Hampton and Quebec City MWCs.26'28 Information
related to the Quebec retrofit program is summarized below.
3.1.3.4.1 Quebec City. Quebec - Background. The goal of Environment
Canada's retrofit program at the Quebec City MWC was to determine the optimum
design and operating conditions to minimize air emissions from the unit and to
retrofit the system to meet these conditions. A profile of the unmodified
design is shown in Figure 3-5. The original design of each combustor includes
a vibrating feeder-hopper and a water-cooled chute that feeds the waste by
gravity. There are three grates (drying, burning, and finishing) in each
unit. The grates have a 15° slope and contain vertical drops between each
section. The furnaces are membrane waterwall construction with a refractory-
lined burning chamber and a mechanically rapped convective section with
superheater and economizer tube sections. Each unit reduces PM emissions with
a two-field ESP that operates at temperatures between 392 and 504°F (200 and
280°C). Bottom ash is discharged from the grates to a wet quench tank and
removed with a drag chain.
3-31
-------
OJ
ho
CM
O
E
u
-------
WATERWALL
MEMBRANE
AUXILIARY
OIL BURNER
SCREEN
TUBES
2nd
CONV.
SECT.
AUXILIARY
OIL
CHAMBER
FRONT
BULL NOSE-
BOILER
DUST
HOPPER
TERWALL
ARCH
REFRACTORY
CHICANE
FLUE GAS
FLOW
BURNING
GRATE
FINISHING
GRATE
DRYING
GRATE
Figure 3-5. Quebec City MWC - Pre-Modification (1978 Design)
3-33
-------
In 1979 a waterwall arch (shown in Figure 3-5) was installed above the
drying and burning grates. Existing side wall overfire air ports were
abandoned in favor of 20 new ports located on the front wall beneath the
waterwall arch. An auxiliary oil burner is also located in the upper front
furnace; however, it was not used. The underfire air fan supplied
approximately 90 percent of the total air flow through five plenums beneath
the grates. The control scheme was largely manual, with the exception that
total underfire air flows were adjusted automatically to maintain steam flow
setpoints.
As mentioned previously, CDD/CDF emissions were measured as part of an
investigation of a pilot dry scrubbing/fabric filter control device study.
Average control device inlet emissions were 1840 ng/dscm. In 1984 Environment
Quebec also conducted CDD/CDF stack testing. Three tests were completed and
CDD/CDF stack emission results varied from 800 to 4000 ng/Nm3.28 Both of
these tests provided a benchmark to compare the effects of the combustion
modifications on emission rates.
3.1.3.4.2 Quebec City MWC Modernization Program. The first step in
the modernization program was the completion of flow modeling studies to
examine the existing furnace flow patterns. The objectives of the modeling
studies were to select a configuration where furnace geometry and airflows
could provide the best mixing of combustion products and adequate retention
times in the furnace for good combustion to occur. The following
modifications were made to the combustor as a result of the flow modeling
study. A profile of the modified configuration is shown in Figure 3-6.
A lower bull nose was added on the rear furnace wall to maximize the
radiation reflection onto the burning and finishing grates, thus providing
improved ash burnout. The bull nose was also designed to pinch the flow of
combustion gases from the finishing grate to mix the combustion products and
complete the burning process. The upper bull nose reduced gas vortices in the
upper portion of the furnace, improving gas distribution and reducing
stratification at the inlet to the convective section. New overfire air
nozzles were installed in the pinched wall section to improve mixing. Various
front-to-rear ratios were examined and a 1:1 ratio was chosen because it
resulted in the optimal vertical mixing and least amount of stratification at
3-34
-------
COMPUTER
WATERWALL
MEMBRANE
FRONT
BULL NOSE"
NEW
REAR
"BULL
NOSE-
NEW PRIMARY
AIR SYSTEM
Figure 3-6. Quebec City MWC - Post-Modification (1986 Design)
3-35
-------
the inlet to the convective section. The reconfiguration also prevented high
velocities in the upper furnace, which helped to reduce PM carryover.
The underfire air supply was redesigned to include nine separate
plenums. The arrangement provided a single plenum under the drying grate, six
individual plenums beneath the burning grate, and two plenums beneath the
burnout grate. Each of the underfire air supplies is individually controlled
to maintain a preset distribution. Total underfire airflows are controlled to
maintain steam production rates. The underfire air system supplies 65 percent
of total combustion air under normal operating conditions and the overfire air
system supplies the remaining 35 percent.
A state-of-the-art automatic combustion controller was installed. The
system automatically controls grate speed in response to boiler steam flow
with an excess air feedback loop to the grate speed controller. Underfire air
flows and distributions are maintained automatically and there are provisions
in the control system to vary overfire air flow rates in response to
temperature readings in the upper furnace.
Following completion of the modernization program, a parametric testing
program was conducted to evaluate the effect of the retrofit on emission
levels. The first phase, characterization testing, investigated the effects
of feed rate, excess air rates, combustion temperatures, and overfire/
underfire air ratios on emissions of CO and other continuously measured gases.
From the results of characterization testing, a series of performance test
conditions were selected for manual sampling of CDD/CDF, and other organic and
inorganic pollutants. All sampling was conducted at the ESP exit location.
Table 3-7 summarizes the results of the CDD/CDF emissions measured during each
performance condition.28
The measured emissions data indicate that the combustion modifications
resulted in substantial reduction of CDD/CDF and CO emissions. Performance
test group #2 (runs 5, 6, 12) can be considered normal operating conditions
for the unit. Average CDD/CDF emissions were reported to be 64 ng/dscm during
the three runs, and average CO emissions were 28 ppmv. Test groups #3 (runs
14 and 15) and #4 (runs 2 and 3) were representative of poor operating
conditions at design steam load. Test groups #1, #5, and #6 investigated the
effects of steam load on emissions performance. Excess air levels were also
varied during these conditions.
3-36
-------
TABLE 3-7. QUEBEC CITY PARAMETRIC TEST - EMISSIONS SUMMARY
TEST GROUP
Runs
Steam flow (Ib/hr)
(kg/hr)
Average excess air (%)
Average Radiation
Temperature (°C)
(°F)
Average combustion
air distribution
(overf i re/under f i re)
Average CDD/CDF
(ng/dscm)
Average CO (ppmv)
I
2, 10, 11
44.000
20,000
(low)
140
864
1587
60/40
191
24
2
5, 6, 12
61,600
28,000
(design)
78
1012
1853
63/35
64
28
3
14, 15
62.400
28.400
(design)
113
978
1792
90/10
550
163
4
3. 4
61,500
28,800
(design)
130
858
1576
60/40
660
78
5
7. 9
70,000
31.800
(high)
84
1046
1915
60/40
174
43
6
13
69.500
31,600
(high)
92
997
1827
60/40
300
77
CO
I
CO
•-J
-------
Figure 3-7 illustrates the reduction in emissions from the 1984
Environment Quebec test results.3° Both of these tests measured stack
emissions levels. Figure 3-8 compares the APCD inlet CDD/CDF emissions
measured during the 1985 pilot study slipstream test with the test group
averages from the parametric test. One important consideration when comparing
these data is the effect of ESP temperatures on CDD/CDF stack emissions. The
average stack temperature during the performance tests varied from 390 to
464°F (199 to 240°C). The extent to which catalytic formation reactions in
the ESP contributed to the stack CDD/CDF emission levels is not known.
The modifications made at the Hampton and Quebec City MWCs addressed the
same design, operating, and control features that were judged to be insuffi-
cient in the small mass burn waterwall model plant (mixing, air distribution,
and control). The CDD/CDF stack emissions were reduced from 10,000-20,000
ng/dscm to 155 ng/dscm at Hampton and from 2000-4000 ng/dscm to 64 ng/dscm at
Quebec (good combustion at design conditions). CO emissions were also reduced
to 24 ppmv at Hampton and 28 ppmv at Quebec. Based on these data, it was
assumed that the combustion retrofit specified for the model plant reduces
CDD/CDF emissions from 2000 ng/dscm to 200 ng/dscm and reduces CO emissions
from 400 ppmv to 50 ppmv (4-hour average). No change in inlet PM emissions is
assumed to result from the modifications.
3.2 Refuse-Derived-Fuel Fired Spreader Stoker MWCs
There are 12 refuse-derived-fuel (RDF) fired plants currently operating
in the U.S. Table 3-8 provides a list of operating plants and their
individual design characteristics. Boiler sizes range from 300 to 1000 tpd
(272 to 909 Mg/day) and the number of boilers at each facility location varies
from 1 to 6. The oldest operating facility is the Akron, OH plant, which
commenced operation in 1979. The majority of the systems are supplied by
Detroit Stoker and B&W. Zurn, Combustion Engineering, and Foster Wheeler also
have shares of the existing market. With the exception of the new B&W units
at Biddeford, ME, which use a new pinched wall lower furnace, all the boilers
are straight wall designs.
Nine of the 12 existing facilities are equipped with ESP controls and
three plants use spray dryers and fabric filters. All three of the plants
that currently use acid gas controls are less than 1 year old. Four of the
3-38
-------
OJ
i
2000 r
39«0
POOR
OPERATION
GOOD
OPERATION
-QUE 184 OLD DESIGN
NITEP "86 NEW DESIGN
Figure 3-7. Comparison of Stack Test Results - Quebec City MWC.
-------
CM
o
E
Q
Q
O
3000
2500-
2000 -
1500-
1000 -
500-
0
*
Good Combustion
Quebec City (pilot)
1985
SD Inlet
x
x
X
-It-
Quebec City
1986
Stack
• Individual run
Q Average
x Average from
test condition
Figure 3-8. Combustion Control - Small Mass Burn Waterwall
-------
TABLE 3-8. EXISTING RDF COMBUSTORS
PLANT LOCATION
Albany, NY
Niagara Falls. NY
Dade County, FL
Akron, OH
Columbus, OH
Lawrence, MA
Red Wing, MN
Mankato, MN
Portsmouth, VA
Biddeford. ME
Orrington, ME
Hartford, CT
MANUFACTURER
STOKER/BOILER
Zurn
Zurn
Detroit Stoker
Foster Wheeler
Detroit Stoker
Fives Cail Babcock*
Detroit Stoker
B&W
Detroit Stoker
B&W
Detroit Stoker
B&W
Detroit Stoker
Foster Wheeler*
Detroit Stoker
B&W*
CE
CE
Detroit Stoker
B&W
Detroit Stoker
Riley
CE
CE
# OF
UNITS
2
2
4
3
6
1
2
2
4
2
2
3
INDIVIDUAL
UNIT SIZE
tpd Mg/day
300 272
1000 909
750 682
300 272
400 364
1000 909
360 327
360 327
480 436
350 318
360 327
667 600
YEAR OF
START-UP
1981
1981
1982
1979
1983
1984
1987
1987
1988
1988
1988
1988
APCD
ESP
ESP
ESP
ESP
Cyclone/
ESP
ESP
ESP
ESP
ESP
SD/FF
SD/FF
SD/FF
ESP INLET
TEMPERATURE
op OQ
450 232
600 316
310 154
525 273
608 320
340 171
420 216
345 174
490 254
-
-
-
00
I
*Undergoing modifications by Zurn.
^Modified by B&W.
-------
nine older plants with ESPs report normal ESP operating temperatures to be
475°F (246°C) or higher. All four of these plants are equipped with
regenerative combustion air pre-heaters vhich are located downstream of the
ESPs.
APCD inlet CDD/CDF emissions data are available from one facility
(Biddeford, ME). Stack emissions data have been reported for five plants.
One plant (Lawrence, MA) has measured CDD/CDF emissions data in the stack
before and after undertaking a combustion retrofit program.
Table 3-9 summarizes the available emissions data from the existing
population of RDF spreader stoker boilers. Also included in Table 3-9 is a
summary of combustor design and operating practices for the units for which
CDD/CDF data are available. Two model plants were developed to represent the
majority of facilities in the existing population. The models represent large
[1600 tpd (545 Mg/day)] and small [<600 tpd (545 Mg/day)] combustor unit
sizes. A discussion of the data used to establish baseline emission estimates
is included below.
3.2.1 Albany. New York
The Albany. NY, RDF fired facility consists of two 300 tpd (272 Mg/day)
spreader stoker boilers. The facility was tested by New York DEC in 1984.
Six sampling runs were conducted in the stack (three while firing 100 percent
RDF and three while co-firing natural gas with RDF). The natural gas
contributed approximately 15 percent of the total heat input. The average
CDD/CDF emissions were 440 ng/dscm while firing RDF and 840 ng/dscm during gas
co-firing.is Particulate emissions at the ESP inlet are reported to be 4.18
gr/dscf (9610 mg/dscm). Continuous monitoring of combustion gases, including
CO, 02, and CO?, was conducted during the sampling runs. Average CO emissions
of 336 ppmv (4-hour average) were measured during the CDD/CDF test without gas
firing. Very limited CO data are available during the MSW/gas firing tests.
and there are no 02 data available to allow correction to 7 percent 02-
However, the uncorrected CO data are in the same range as the CO emissions
measured during the 100 percent RDF tests.
The natural gas burners are located on the rear wall approximately half
way between the grate and the overfire air ports. It is suspected that the
location of the burners may have contributed to the higher emission levels by
3-42
-------
TABLE 3-9. RDF FIRED SPREADER STOKERS- PERFORMANCE ASSESSMENT
PAGE 1 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
GOOD COMBUSTION
PRACTICE RECOMMENDATIONS
Albany. NY
2 - ESP
300 (272)
NA
NA
9610
432
336
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Ai r distribution
Exit gas temperature
1800°F (982°C) mean
As required for uniform
bed stoichiometry
40% total air
Coverage and
penetration
As required to achieve
temperature limits
during start-up
<450°F (232°C) at PM
control device inlet
3-9% 02 (dry)
80-110% design load
Penetration and coverage
Auxiliary fuel
High CO, low temp;
start-up/shutdown
Monitor
Monitor «150 ppm at 7% 02))
Monitor
Monitor
Monitor
1200°F (649°C) at inlet
to convective section
1 plenum
20% total air
Not used
Gas - 100% load
400-450°F (204-232°C)
5.5-10%
50-100% of design
Not achieved
Gas - 400°F (204°C)
at ESP inlet
Start-up/shutdown
Yes
Yes
Yes
NA
Yes
3-43
-------
TABLE 3-9. RDF FIRED SPREADER STOKERS- PERFORMANCE ASSESSMENT
PAGE 2 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Niagara Falls. NY
2 - ESP
1000 (909)
204
7480
4246
FACILITY DESIGN
AND OPERATING CONDITIONS
Lawrence, MA
1 - ESP
1000 (909)
3304
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
1600°F (871°C) at inlet
to convective section
2 plenums with individual
controls
45% of total air
3 rows
Gas, oil. H2. coal -
100% load
600°F (316°C)
10% 02
50-80% design load
45% total air
Gas to 1500°F (871°C)
or 20% steam flow
Start-up; feed interruptions
NA
NA
At least 75% total air
NA
Oil - Na
542°F (283°C)
9.4% 02
NA
75% total air
NA
NA
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
Yes
Yes
Yes
OFA/UFA pressures
Yes
Yes
NA
Yes
Yes
Yes
3-44
-------
TABLE 3-9. RDF FIRED SPREADER STOKERS- PERFORMANCE ASSESSMENT
PAGE 3 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Biddeford. ME
2 - SD/FF
300 (272)
903
81
8190
FACILITY DESIGN
AND OPERATING CONDITIONS
Red Wing. MN
2 - ESP
360 (318)
NA
127
4900
28
99
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Underfire air
Overfire air capacity
Overfire air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Overfire air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
NA
Metered fuel feeding
60% total air
Gas - 40% load
374°F (190°C)
7% 02
40% minimum (on gas)
60% total air
Gas to 1800°F (982°C)
Routinely co-fire,
start-up, shutdown
Yes
No
Not currently measured
NA
Yes
>1800°F (982°C) at inlet
to first convective
section
2 plenums
50% total air
100% load
260-450°F (127-232°C)
7-11% 02
40% minimum
50% at full load
20% at minimum load
Gas
Start-up
Yes
Yes
Yes
Yes
Yes
3-45
-------
disrupting mixing patterns in the boiler and increasing vertical velocities of
gases in the lower portion of the system. The ESPs reportedly operate near
450°F (232°C). Plant personnel reported during a site visit that the use of
overfire air has been discontinued as a result of performance optimization
tests.i
A review of design and operating practices at Albany indicates that the
facility does not meet the recommended requirements for overfire air system
design and operation. In addition, the traveling grate is a single speed
stoker (not adjustable), and there is only one underfire air plenum.
3.2.2 Niagara Falls. New York
The Occidental Chemical Corporation RDF facility in Niagara Falls, NY
comprises two 1000 tpd (909 Mg/day) spreader stoker boilers with four-field
ESPs. The ESPs normally operate at 570 to 600°F (299 to 316°C). The plant
was originally tested in 1985 by New York State. Stack CDD/CDF concentrations
were reported to be 2561 ng/dscm and controlled PM emissions were 0.096
gr/dscf.15 The ESPs were subsequently rebuilt and the system was retested.
Particulate emissions were reduced to 0.012 gr/dscf; however, CDD/CDF
emissions in the stack increased to 4246 ng/dscm.30
Several modifications have been made to the overfire air system in the
last few years in an attempt to improve mixing. Based on review of the
measured emissions, it appears that mixing and air distribution problems
continue to exist despite the modifications. Slagging and corrosion problems
have also led to higher excess air operating levels, which may contribute to
high organics emissions as a result of quenching and increased PM carryover.1
No ESP inlet CDD/CDF emissions are available for the facility, but it is
judged that a portion of the CDD/CDF in the stack results from catalytic
formation in the hot ESP. Average unabated particulate emissions were 3.25
gr/dscf (7580 mg/dscm) and CO emissions ranged from 200 to 250 ppmv. both
corrected to 7 percent QZ-
3.2.3 Lawrence. Massachusetts
The Lawrence. MA. plant includes one RDF spreader stoker boiler rated at
1000 tpd (909 Mg/day) of RDF. The unit was tested in 1986 and CDD/CDF
emissions in the stack were reported to be 3304 ng/dscm.31 Like Niagara
3-46
-------
Falls, the Lawrence facility was designed with a hot side ESP. The RDF boiler
was operated at 83 to 87 percent of rated steam load during the test. The
overfire airflow comprised more than 70 percent of the total air input to the
system. The average flue gas temperature at the economizer was 542°F (283°C).
There is insufficient information available on the design of the unit from
which an assessment of its performance can be made relative to recommended
good combustion practices. The unit was shut down voluntarily after the
initial compliance test. A combustion retrofit was undertaken between 1986
and 1987, and the unit was brought on line again and retested in 1987. Stack
CDD/CDF emissions were reduced to 111 ng/dscm.3? No process operating data
are included with the test results, and the details of the combustion retrofit
have not been made public.
3.2.4 Biddeford. Maine
The Biddeford. ME. MWC was tested for CDD/CDF by EPA in December 1987.
The plant comprises two boilers, each rated at 350 tpd (318 Mg/day) RDF.
Emissions control on each unit is achieved by a cyclone, a spray dryer, and a
baghouse. Emissions were measured at the spray dryer inlet (downstream of the
cyclone) in conjunction with compliance testing performed in the stack. The
unit that was tested was operating at full load during the test. Although an
RDF/wood mixture is fired during normal operating conditions, 100 percent RDF
was burned during the test. Three CDD/CDF sampling runs were performed and
average unabated emissions were 903 ng/dscm.33 Inlet particulate emissions
were 3.56 gr/dscf (8190 mg/dscm). and average CO emissions were 81 ppmv. The
boiler was operated at approximately 65-70 percent excess air during the test
with an overf i re/underfi re ratio of 56/44. Each test run was 4 hours'
duration. The average temperature at the spray dryer inlet location was 374°F
(190°C).
3.2.5 Red Wind. Minnesota
The Red Wing facility comprises two 35-year-old coal-fired spreader
stoker boilers that have been retrofitted to burn 100 percent RDF.3* The
boilers were enlarged by extending the furnace down into the basement.
removing the coal bottom ash hoppers, lowering the stokers, and adding a 14-
foot (4.3-m) waterwall extension fabricated from membrane panels with high
nickel alloy weld overlay. The existing tube and tile upper furnace was
connected to the new membrane walls by installation of a transition header. A
3-47
-------
new multilevel, multipoint, heated overfire air system was installed to ensure
good mixing.
The facility was tested for CDD/CDF in 1987. Emissions at the ESP inlet
were reported to be 60 ng/dscm, and average stack emissions were 28 ng/dscm.35
Inlet particulate emissions were reported to be 2.13 gr/dscf (4900 mg/dscm),
and average CO levels were 127 ppmv (5-hour average). The Red Wing units are
designed to operate at 65 percent excess air with a 50/50 overfire/underfire
air ratio. The average excess air level was 62 percent during CDD/CDF
testing, and the air distribution was not specified. The design ESP inlet
temperature is 420°F (216°C), and the average operating value was 425°F
(218°C).
After the data were subjected to an EPA QA/QC review, the inlet CDD/CDF
data were invalidated. Therefore, only the data measured in the stack were
included in this analysis.
3.2.6 Baseline Emission Estimates
The two model plants representing existing RDF spreader stokers are
distinguished mainly by size. The only major design feature that varied
between the two model plants was the location and type of air heater. Based
on the characteristics of the existing population, the large model plant was
assumed to have a regenerative air heater located downstream of the ESP. The
small model plant was assumed to use a tubular air heater located between the
economizer and the ESP. Thus, the ESP on the large model plant is operated at
a higher temperature, and it is judged that there is increased potential for
catalytic formation of CDD/CDF in the control device.
The available emissions data used to establish baseline CDD/CDF
emissions for RDF spreader stokers are plotted in Figure 3-9. The data from
the Lawrence facility include only those emissions measured prior to the
retrofit. The range of measured data varies greatly for all units in the
population. There is no pattern in emissions that can be established based on
unit size or manufacturer. There are facilities in the existing population
which achieve many of the recommended good combustion practices for RDF
spreader stokers. However, many plants in the population do not meet the
criteria for good combustion, and the model plants are assumed to be more
representative of these facilities. It is judged that the high CDD/CDF
3-48
-------
CDD/CDF (ng/dscm at 7% O2)
3
(Q
C
CD
CO
«> V)
3J |
D ^
~n m
O £
o -~-
cr
c
w
o
(A
CO
5'
O D $5
-• 3! 5r
n^
6'
o
0
5"
CD
-1 M co -d cn c
8 8 8 8 8 S
o o o o o o c
1 . 1 1 1 • 1
Albany Gas Off
Albany Gas On
Niagra Falls
Pre-ESP Rebuild
Niagra Falls
Post-ESP Rebuild
Lawrence
Pre-Retrofit
Red Wing
RiHHrfnrH
PiHHnfnrH
OlUUCslUlU "
.
D
Q
1
I
CD
• •D •
• Q •
• • Q •
I f
CL
CO
CD
-------
emission levels at the Niagara Falls plant and the unmodified Lawrence
facility are partly due to catalytic formation in the hot ESPs. The magnitude
of the emissions increase is uncertain and cannot be determined using the
available data. It was assumed in this analysis that the hot ESP contributes
a net increase of CDD/CDF emissions of approximately 50 percent based on test
data gathered at mass burn waterwall MWCs with hot ESPs.8-9 Using this
assumption, a baseline APCD inlet CDD/CDF emission rate of 2000 ng/dscm was
established for both of the RDF spreader stoker model plants. The available
CO emissions data base was used to establish a baseline CO emission level of
200 ppmv. The available PM emission data base was used to establish baseline
emissions of 4 gr/dscf (9600 mg/dscm). Unabated PM emissions are typically
higher from spreader stoker boilers than from other MWC technologies because
of the semi-suspension firing mode.
3.2.7 Combustion Modifications
Fairly extensive modifications were recommended for each of the RDF
model plants in order to bring their emission performance to levels
representing good combustion practice. Both models required installation of
metered feeding systems, redesigned overfire air systems, new automatic
combustion controllers, and CO monitors for verification of good combustion.
In addition, it was necessary to convert the hot ESP in the large RDF model to
a cold side ESP by rearranging the ducting so that the flue gases enter the
air heater prior to the ESP. It was estimated that the modifications at each
model facility would reduce inlet CDD/CDF emissions from 2000 ng/dscm to 1000
ng/dscm and CO emissions from 200 ppmv to 150 ppmv.
The basis for the estimated emission reductions was formulated by using
engineering judgement. It was judged that the recommended combustion
modifications would reduce emissions to levels comparable to the Biddeford, ME
plant, a new RDF fired facility.
3.3 Mass Burn Refractory Wall MWCs
The current population of mass burn refractory wall MWCs consists of 24
plants. Table 3-10 lists the facilities operating in 1988. Individual
incinerator unit sizes vary from 88 to 375 tpd (80 to 341 Mg/day). The
majority of the facilities are at least 15-20 years old. Three plants include
relatively new units: the Tampa, FL plant commenced operation in 1985 using
3-50
-------
TABLE 3-10. EXISTING MASS BURN REFRACTORY WALL COMBUSTORS
PLANT LOCATION
Batch Feed
Stamford I, CT
Huntington, NY
Continuous Feed
Philadelphia NW, PA
Philadelphia EC, PA
E Chicago, IN
SE Oakland County, MI
Honolulu. HI
New York, NY (Betts Ave)
Clinton, MI
Euclid. OH
Fall River, MA
New Canaan, CT
Washington, DC
Baltimore. MD (Pulaski )
SW Brooklyn, NY
Waukesha. WI
Stamford II, CT
Sheboygan, WI
Huntington, NY
N Dayton. OH
S Dayton, OH
Louisville, KY
Framingham. MA
Tampa, FL (McKay Bay)
GRATE TYPE
Traveling
Traveling
Traveling
Traveling
Traveling
Traveling
Reciprocati ng
Reciprocating
Reciprocating
Reciprocating
Rocki ng
Reciprocating
Reciprocating
Reciprocating
Rocking
Rocking
Rocking
Grate/rotary kiln
Grate/rotary kiln
Grate/rotary kiln
Grate/rotary kiln
Grate/rotary kiln
# OF
UNITS
1
2
2
2
2
2
2
4
2
2
2
1
4
4
4
2
1
2
1
3*
3t
4
2
4
INDIVIDUAL
UNIT SIZE
tpd Mg/day
150 136
150 136
375 341
375 341
225 205
300 272
300 272
250 227
300 272
100 91
300 272
125 114
250 227
300 272
240 218
88 80
360 327
120 109
150 136
300 272
300 272
250 227
250 227
250 227
YEAR OF
START-UP
1953
NA
1957
1965
1971
1965
1970
1960
1972
1955
1972
1971
1972
1954
1959
1971
1974
1965
1963
1970
1988
1970
1988
1956
1973
1985
APCD
ESP
Water sprays
ESP
ESP
Venturi scrubber
Venturi scrubber
ESP
ESP
ESP
ESP
Wet scrubber
Venturi scrubber
ESP
ESP
ESP
ESP
ESP
Water sprays
ESP
ESP
ESP
Wet scrubber
Dry scrubber/FF
ESP
ESP INLET
TEMPERATURE
°F °C
NA* NA
-
550 288
550 288
-
-
450 209
550 288
500 254
550 288
-
-
500 254
500-600 254-316
NA NA
450 209
NA NA
-
NA NA
600 316
600 316
-
-
550 288
CO
I
en
*NA - Information not available.
with heat recovery. tThis plant
*This plant has recently added a third unit of similar design.
has recently added a third unit of similar design.
-------
four 250 tpd (227 Mg/day) Volund combustors with waste heat recovery boilers.
Facility expansions have occurred at two plants (North and South Montgomery
County. OH), with installation of a third 300 tpd (272 Mg/day) combustor at
each location in 1988. The North plant was constructed with a waste heat
recovery boiler and the South plant provided space for a future boiler
installation.
Four distinct design types are used in the existing population. The
first and oldest design is a batch fed unit which is in place at two locations
(Stamford. CT and Huntington. NY). At one time the population included many
of these systems, but most have been closed in the last two decades.
A second design type is the rectangular incinerator with traveling
grates. There were six facilities of this type identified in the existing
population, although two plants in Philadelphia (Northwest and East Central)
and the plant in Southeast Oakland County, MI were permanently shut down in
1988. These closures reduce the number of existing plants using this design
to three.
A third design also uses a rectangular incinerator similar in configura-
tion to the second type, but this design uses rocking or reciprocating grates
to agitate the burning waste bed as it moves through the incinerator. This
feature improves the ability of the combustor to achieve waste burnout.
Eleven plants of this type have been identified in the existing population.
The last combustor design uses a split flow configuration with recipro-
cating grates and a rotary kiln. There are five plants of this type, one of
which is Tampa, FL, a relatively new Volund design. The other plants are
early vintage Volund units or adaptations thereof.
Sixteen of the existing MWCs use ESPs for participate removal. Due to
the high gas temperatures leaving a non-heat recovery facility, wet quench
systems are always in place to reduce gas temperatures before they enter an
ESP. Seven existing plants use wet controls (spray chamber, venturi
scrubbers, or impingement scrubbers) without additional PM controls. One
facility in Framingham, MA is equipped with a spray dryer and fabric filters.
Review of available information related to flue gas temperatures indicates
that at least 10 facilities (32 units) operate ESPs at temperatures between
500 and 600°F (260 and 316°C).
3-52
-------
3.3.1 Emissions Data
3.3.1.1 Philadelphia NW and EC. Pennsylvania
The available CDD/CDF emissions data from mass burn refractory wall MWCs
are limited to test results from only 1 of the 24 plants in Table 3-10. Both
units at the Philadelphia NW plant were tested for CDD/CDF in 1985 under
normal operating conditions. Three sampling runs were conducted for CDD/CDF
in the stack, downstream of the wet quench/ESP control system. Average
CDD/CDF emissions were reported to be 5923 ng/dscm from Unit #1 and 5915
ng/dscm from Unit #2.36 Only two runs are included in the average for Unit #1
because a low surrogate sample recovery was reported for one run. The
sampling runs and average values are presented graphically in Figure 3-10.
Results of CO monitoring performed during the test indicated average emissions
of 447 ppmv at Unit #1 and 821 ppmv at Unit #2. The units do not produce
steam or monitor feed rates directly. Continuous 02 monitors in the stack
indicated that the units operated an excess air level ranging from 180 to 260
percent during the test. During a visit to the facility, numerous points of
air inleakage were observed in the system.1 The stack gas temperature ranged
from 508 to 515°F (265 to 269°C) at Unit #1 and 503 to 518°F (262 to 270°C) at
Unit #2. Carbon monoxide emissions were also measured at the Philadelphia
East Central (EC) plant, which is similar in design and identical in capacity
to the Northwest facility. Average CO emissions from the two EC units were
reported to be 140 and 51 ppmv. respectively.36 Excess air levels during
testing were approximately 275 percent at Unit 1 and 390 percent at Unit #2.
There are no additional process data available.
3.3.1.2 Foreign Data
Data summaries are reported for several other refractory wall
incinerators in the MWC Emissions Data Base Volume of the Report to Congress.
Although there is limited documentation for most of the emission values, the
data are comparable to the stack values reported for Philadelphia NW. Stack
emissions reported for four plants (Toronto, Ontario; Braschatt, Belgium:
Harelbeke, Belgium; and Zaanstad. Netherlands) vary from 5320 to 6850
ng/dscm.23 Emission control device temperatures are not available for these
data sets.
3-53
-------
OJ
i
en
CM
O
5?
E
u
CO
O
U
Q
O
O
8000
6000 -
•
D
•
4000
2000 -
Unitl
Unit 2
Q Average
• Individual Run
Philadelphia Pre-Retrofit
Stack (ESP)
Figure 3-10. Mass Burn Refractory Baseline Determination
-------
3.3.2 Baseline Emission Estimates
Three model plants were developed to represent the existing population
of mass burn refractory wall MWCs. The model configurations include two
rectangular combustors, one with traveling grates and one with rocking grates,
and one split flow design with grates and a rotary kiln. None of the model
plants incorporates heat recovery into its design. Due to the limited
availability of emissions data from mass burn refractory wall combustors. a
single baseline emission level was established for the three model plants.
Comparing the emissions data from Philadelphia NW to those data gathered
from foreign plants, it appears that the majority of existing refractory wall
MWCs could potentially have high emissions. The majority of refractory wall
incinerators were designed with a primary goal of waste volume reduction, and
concerns regarding levels of trace organic emissions did not exist at the time
they commenced operation. The recommended good combustion practices for mass
burn refractory wall MWCs require good mixing at adequate temperatures for
thermal destruction of trace organic compounds, and minimization of conditions
that may cause formation of these compounds in low temperature regions of the
system. None of the existing mass burn refractory wall model MWCs meets both
of these criteria.
The ESP operating temperature at the Philadelphia units [550°F (288°C)]
likely contributes to the high CDD/CDF emission values. It is assumed that
formation of CDD/CDF in the ESP accounts for a 50 percent increase over the
uncontrolled emission values. Therefore, uncontrolled baseline CDD/CDF
emissions are assumed to be 4000 ng/dscm. Average carbon monoxide emissions
data from Philadelphia NW and Philadelphia EC vary from 51 to 821 ppmv. A
conservative average of 500 ppmv was assumed as a baseline CO emission level.
Inlet PM emissions are assumed to be 3 gr/dscf (6900 mg/dscm). Baseline APCD
inlet PM emissions for the mass burn waterwal 1 models are 2 gr/dscf (4600
mg/dscm). Waterwall plants usually operate at 80-100 percent excess air. The
refractory wall models operate at 200-300 percent excess air in the baseline
condition. It is assumed that higher airflows will contribute to increased
carryover of particulate from the combustor.
3-55
-------
3.3.3 Combustion Modifications
The basis for the estimated emission reductions applied to the
refractory wall model plants comes from test data gathered at Philadelphia NW.
The plant was retested in December 1987 after modifying the configuration of
the upper combustion chamber to increase flue gas residence time. Refractory
lined structural steel arches were installed to improve mixing of flue gases
in the upper combustion chamber. In addition, the location of the existing
water quench sprays was moved 25 feet (7.6 m) downstream in the furnace
discharge breeching to provide increased residence time at high temperatures.
Average stack CDD/CDF emissions were reduced to 1000 ng/dscm.37 Figure 3-11
compares the 1987 and the 1985 CDD/CDF emissions data reported for the two
units at Philadelphia NW. The ESP operating temperature was not reduced as
part of the modification. Therefore, it is judged that the ESP inlet CDD/CDF
emissions are lower than 1000 ng/dscm.
The proposed modifications for the three model plants are far more
extensive than those made at Philadelphia NW. They include changes in furnace
geometry; excess air rates and air distribution; modifications to combustion
control systems; and, in the case of the traveling grate model, replacement of
the stokers with reciprocating grates. It is judged that the combined effects
of these modifications will enable the three model plants to achieve CDD/CDF
emissions of 500 ng/dscm at the APCD inlet.
Reduction of excess air levels and improved mixing will also contribute
to lower CO emissions. It is assumed that the combustion modifications, which
include reducing excess air levels and improving mixing, will reduce CO
emissions to 150 pptnv. No other changes in emissions are assumed to occur as
a result of the modifications.
3.4 Mass Burn Modular Starved Air MWCs
There are nearly 50 modular starved air plants in the existing MWC
population. Table 3-11 presents a list of these facilities. Individual
combustor capacities range from 5 to 90 tpd (4.5 to 82 Mg/day). with one to
four units per facility location. The facilities range in age from new to 17
years. Thirty-one of the 49 existing plants in Table 3-11 use heat recovery
boilers, and the remainder are simply waste volume reduction plants. Most of
the larger, newer facilities are equipped with add-on air pollution control,
3-56
-------
/uuu -
O 6000 -
h-
5000 -
(0
E
g 4000 -
O)
•^ 3000 -
u.
Q
O
^ 2000 -
Q
O
w 100°-
1
cn
^ 0-
Q Q
^
Good Combustion ' '
"5 "o "o "o
0 ® CO 0
cc cc tr cc
i w 2 w
1 1 1
Q Average
• Individual Run
Unit 1 - Stack (ESP)
Unit 2 - Stack (ESP)
Figure 3-11. Combustion Control - Refractory
-------
TABLE 3-11. EXISTING MODULAR STARVED AIR COMBUSTORS
page 1 of 2
PLANT LOCATION
CQNSUHAT SYSTEMS
Bel 1 i ngham, WA
Auburn, NH
Wolfboro, NH
Litchfield, NH
Newport News. VA
Carthage, TX
Center, TX
Batesville. AR
Cassia County, ID
Johnsonvil le, SC
Osceola, AR
Wrightsville Beach, NC
Red Wing, MN
Livingston, MT
Barren County, WI
Dyersburg. TN
Salem, VA
N Little Rock, AR
Durham, NH
Miami , OK
Windham, CT
Oswego, NY
Auburn, ME
Portsmouth, NH
Hampton, SC
Harford County, MD
Wilton. NH
Stuttgart. AR
Tuscaloosa, AL
Coos Bay. OR
# OF
UNITS
2
1
2
1
1
1
1
1
2
1
2
2
2
2
2
2
4
4
3
3
3
4
4
4
3
4
1
3
4
2
2
UNIT SIZE
tpd Mg/day
50 45
5 4.5
8 7.3
22 20
35 32
36 33
36 33
50 45
25 23
50 45
25 23
25 23
45 41
38 35
40 36
50 45
25 23
25 23
36 33
35 32
36 33
50 45
50 45
50 45
90 82
90 82
30 27
23 21
75 68
12.5 11
50 45
YEAR OF
START-UP
1986
NA
1975
NA
1980
1985
1985
1981
1982
NA
1980
1981
1982
1982
1986
1980
1977
1977
1980
1982
1981
1986
1981
1982
1985
1987
1978
1971
1984
1978
1980
HEAT
RECOVERY
yes
no
no
no
yes
yes
yes
yes
yes
yes
yes
no
yes
yes
no
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
no
yes
no
no
APCD
none
none
none
none
none
none
none
none
none
ESP
none
none
ESP
none
ESP
none
none
none
cyclone
none
none
ESP
fabric filter
fabric filter
ESP
ESP
none
none
ESP
none
none
INLET TEMPERATURE
op oC
.
-
-
-
-
-
-
-
-
NA NA
-
-
550 288
-
425 218
-
-
-
NA NA
-
-
450 232
550-600 288-316
NA NA
NA NA
NA NA
-
-
450 232
-
-
CO
I
en
oo
-------
TABLE 3-11. EXISTING MODULAR STARVED AIR COMBUSTORS
page 2 of 2
PLANT LOCATION
# OF
UNITS
CONSUMAT SYSTEMS (cont'd)
Blytheville, AR
Juneau, AK
Brookings, OR
Windham, ME
KELLY SYSTEMS
Canterbury, NH
Candia. NH
Meredith, NH
Pittsfield, NH
ECP SYSTEMS
Groveton. NH
Fort Leo. Wood, MO
CLEAR AIR/SYNERGY
Fort Dix. VA
Perham, MN
Waxahachie, TX
Cattaraugus, NY
Oneida County, NY
JOHN ZINK
Westmoreland
County, PA
Fergus Falls, MN
Polk County, MN
SUNBEAM
Pelham, NH
2
2
2
2
1
1
2
1
1
3
4
2
2
3
4
2
2
2
2
UNIT SIZE
tpd Mg/day
36 33
35 32
24 21
22 20
10 9.2
15 14
15 14
48 44
24 21
26 24
20 18
57 52
25 23
38 35
50 45
25 23
38 35
40 36
24 21
YEAR OF
START-UP
1983
1985
1979
1975
NA
1979
NA
NA
1980
1982
1986
1986
1982
1983
1985
1986
1988
1988
1987
HEAT
RECOVERY
no
no
no
no
no
no
no
no
yes
yes
yes
yes
yes
no
yes
yes
yes
yes
no
APCD
none
ESP
none
none
none
none
none
none
none
none
FF/VWS/
packed tower
ESP
none
none
ESP
ESP
WS/Venturi
ESP
none
INLET TEMPERATURE
op oC
-
800 427
-
-
-
-
-
-
-
-
-
425 218
-
-
400-470 204-243
480 249
-
475 246
-
CO
I
en
-------
although older plants, less than 50 tpd (45 Mg/day). typically do not have
APCDs. Only 17 plants reportedly use add-on controls, and the majority of
these are ESPs. Two existing facilities report ESP operating temperatures in
the 500-600°F (260-316°C) range.
Thirty-four of the existing plants are Consumat designs, which use
transfer rams in the primary chamber for waste movement. The Clear Air
designs use reciprocating grates, and the other designs are similar to
Consumat. The Clear Air systems also typically operate with slightly higher
temperatures in the primary chamber than the Consumat units, typically 1600-
1800°F (871-982°C) versus 1400-1600°F (760-871°C).
3.4.1 Emissions Data
Emissions of CDD/CDF have been reported for four existing facilities.
Stack emissions are available from Cattaraugus County, NY and Charlottetown,
PEL Both of these plants have no add-on controls. Stack emissions are
reported from Oneida County, NY and Red Wing. MN. Cattaraugus County and
Oneida County are Clear Air units, and the two others are Consumat designs.
The available emissions data are presented in Table 3-12 along with a summary
of individual plant design and operating practices. More information on
individual emission tests is presented below.
3.4.1.1 Prince Edward Island
Emissions testing was performed at PEI at four operating conditions
(normal, long feed cycle, high secondary chamber temperature, and low
secondary chamber temperature). The facility consists of three Consumat CS-
1600 combustors. each rated at 36 tpd (33 Mg/day). The combustors exhaust to
a common waste heat recovery boiler and then to a stack without further
emissions control. A process schematic of the facility is provided in Figure
3-12. Sampling was performed at the boiler inlet location and in the stack.
The primary operating variables were primary and secondary combustion
temperatures and feed cycle. Three sampling runs were performed for each
condition. The average CDD/CDF and CO data are presented in Table 3-13 for
each operating condition.6
The data in Table 3-13 indicate that CDD/CDF emission levels in the
stack are partially due to formation that occurs in the lower temperature
3-60
-------
TABLE 3-12. MODULAR STARVED AIR MWCS - PERFORMANCE ASSESSMENT
PAGE 1 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Prince Edward Island
3 - None
36 (33)
409
62
225
GOOD COMBUSTION
PRACTICE RECOMMENDATIONS
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Secondary air capacity
(not an operating
requi rement)
Secondary air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Secondary air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1800°F (982°C) average
80% total air
That required for penetration
and coverage
As required to achieve
temperature limits
during start-up
<450°F (232°C) at PM
control device inlet
6-12% 02 (dry)
80-110% design load
80% total air
On auxiliary fuel to
design temperature
High CO. low temp;
start-up/shutdown
Monitor
Monitor «50 ppm at 7% 02))
Monitor
Monitor
Monitor
1832°F (1000°C)
(secondary chamber)
NA
NA
NA
363°F (184°C)
12% 02
NA
NA
NA
NA
No
No
Primary and
secondary chamber
No
No
3-61
-------
TABLE 3-12. MODULAR STARVED AIR MWCS - PERFORMANCE ASSESSMENT
PAGE 2 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Cattaraugus County. NY
3 - None
38 (35)
345
NA
Oneida County. NY
4 - ESP
50 (45)
FACILITY DESIGN
AND OPERATING CONDITIONS
462
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Secondary air capacity
(not an operating
requi rement)
Secondary air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Secondary air
Start-up procedures
Auxiliary fuel use
1800-2000°F (983-1093°C)
(secondary exit)
At least 40% total air
NA
Gas - 30% load
502°F (216°C) (stack)
NA
NA
40% of total air
On gas to 1800°F (983°C)
in secondary
Start-up
1800°F (983°C)
(secondary exit)
NA
NA
Gas - 100% (not used)
400-450°F (204-232°C)
(boiler outlet)
NA
NA
NA
Not used
None
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
No
No
Primary and secondary
chamber
Primary air
Yes
No
No
Primary and secondary
chamber
No
Yes
3-62
-------
TABLE 3-12. MODULAR STARVED AIR MWCS - PERFORMANCE ASSESSMENT
PAGE 3 OF 3
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
COD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
COD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
Red Wing. MN
2 - ESP
45 (41)
3358
2
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed height
Secondary air capacity
(not an operating
requirement)
Secondary air injector
design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Secondary air
Start-up procedures
Auxiliary fuel use
1800°F (983°C) (secondary exit)
NA
Gas - NA
550-600°F (288-316°C)
10-12% 02
NA
MA
Gas - not used
Not used
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
Yes
No
Primary and secondary chamber
No
Yes
3-63
-------
CO
I
01
QUENCH
TANK
Figure 3-12. Prince Edward Island MWC.
-------
TABLE 3-13. PERFORMANCE TEST DATA
PRINCE EDWARD ISLAND MWC
CONDITION
Normal
Long Cycle
High Secondary
Low Secondary
BOILER INLET
CDD/CDF
(ng/dscm)
NA
0
1
42
TEMPERATURE
°F °C
1544 840
1544 840
1922 1050
1364 740
STACK
CDD/CDF
(ng/dscm)
409
441
198
424
CO
(ppmv)
62
39
38
53
TEMPERATURE
op oC
363 184
363 184
361 183
266 130
3-65
-------
portions of the system. With the exception of the low secondary temperature
conditions. CDD/CDF emissions are near zero at the boiler inlet. The higher
emission levels during the low secondary temperature condition likely results
from insufficient temperatures to provide destruction of CDD/CDF and
precursors. Secondly, the operating variable that had the most noticeable
effect on CDD/CDF stack emissions was the high secondary chamber temperature.
These data provide support for the combustion temperature requirements in the
MWC recommendations.
3.4.1.2 Cattarauous County. New York
The second set of CDD/CDF emissions data was gathered at the Clear Air
facility in Cuba (Cattaraugus County). NY. The plant consists of three 38 tpd
(35 Mg/day) units that began operating in 1983. The plant has heat recovery
but uses no flue gas cleaning device. Two CDD/CDF sampling runs are available
from testing performed by New York State DEC in 1984. and average emissions
were reported to be 345 ng/dscm.is There are no CO data available with the
test results. Primary chamber temperatures were approximately 2200-2300°F
(1204-1260°C) and secondary chamber temperatures were maintained near 2000°F
(1093°C) during testing.
3.4.1.3 Oneida County. New York
Oneida County is another Clear Air facility which comprises four units
at 50 tpd (45 Mg/day) each. The plant has heat recovery in place and is
equipped with an ESP. Stack testing was performed by New York State DEC in
1985. Average CDD/CDF emissions at Unit #1 were 462 ng/dscm.i& The
temperature at the ESP inlet was 458°F (237°C). Primary chamber temperatures
were approximately 1600-1800°F (871-982°C) and secondary chamber temperatures
were 1700-2000°F (927-1093°C) during testing.
3.4.1.4 Red Wino. Minnesota
The Red Wing. MN facility includes two 45 tpd (41 Mg/day) Consumat units
with a waste heat boiler and ESP controls. The facility was sampled for
CDD/CDF and other pollutants in the stack in September 1986. The available
process data indicate that temperatures ranged from 1400 to 1600°F (760 to
871°C) in the primary chambers and 1750 to 1960°F (954 to 1071°C) in the
secondary chamber. These temperatures are typical for Consumat designs in
3-66
-------
general, and in the same range as those measured at the other Consumat systems
that achieved low CDO/CDF emissions. The average CO data were also extremely
low «2 ppmv). indicating good combustion in the primary and secondary
chambers. However, average CDD/CDF emissions in the stack were 3358
ng/dscm.38 The ESP operated at a temperature of 590-600°F (310-316°C) during
the tests. It is judged that the high CDD/CDF emissions in the stack result
from formation in the ESP.
3.4.2 Baseline Emission Estimates
The available emissions data provide evidence that relatively low
CDD/CDF concentrations can be achieved by modular starved air MWCs. The key
conditions that lead to low emissions are the same as specified for other
technologies: achieve good mixing at adequate temperature and minimize the
conditions that lead to downstream formation of CDD/CDF. Starved air MWCs can
achieve adequate secondary chamber temperatures by control of air flows. The
fully mixed location in a modular starved air MWC can be defined at the exit
of the secondary combustion chamber. The available data also indicate that
total elimination of downstream formation of CDD/CDF may not be feasible.
However, systems should be designed and operated in a manner which minimizes
the potential for these occurrences. The emissions data used to establish
baseline emissions for the model plants are presented in Figure 3-13. Based
on the available data from Cattaraugus. Oneida. and PEI. baseline CDD/CDF
emissions were assumed to be 400 ng/dscm. The Red Wing data were not used to
support baseline emissions because the high emission levels are suspected to
result from formation in the ESP, and the emission levels upstream of the ESP
are unknown. Based on the average CO emissions of 62 ppmv measured at PEI.
baseline CO emissions are assumed to be 100 ppmv. Baseline PM emissions were
established at 0.15 gr/dscf (345 mg/dscm) using data from PEI. The baseline
emissions were applied to both of the modular starved air model plants.
i
3.4.3 Combustion Modifications
Modifications required for the model plants included installation of
continuous monitors for verification of 0? and CO operating levels. In
addition, an economizer was added to the larger model to reduce flue gas
temperatures entering the ESP. Although the modifications did not change
uncontrolled emission levels, stack CDD/CDF emissions were reduced by lowering
3-67
-------
cc
Q) "5
05 -O
1 1
• Q •
6uo-|
(aodv ON)
0)
"5
to
TO
1
O
5
c
0)
OT
ra
«
O)
O
o
r^-
o
O
CD
LO
o
O
CO
o
O
CNJ
o
O
(ZO %L JB mosp/Bu)
3-68
-------
ESP operating temperatures, thus preventing CDD/CDF formation in the control
device.
3.5 Mass Burn Modular Excess Air MNCs
Sixteen existing facilities comprise the population of mass burn modular
excess air MWCs. Table 3-14 presents a list of these plants. Unit sizes vary
from 8 to 120 tpd (7.3 to 109 Mg/day). with one to five combustors per
facility location. The existing population includes some very different
designs, including Vicon/Enercon. Cadoux. and Sigoure Freres. A decision was
made in the Retrofit Study to develop a model plant based on the Vicon/Enercon
design. There are 3 existing plants of this design type, and these 3 plants
have a greater total capacity than the other 13 existing plants combined. The
Vicon/Enercon units incorporate some very distinct design features, including
a tertiary duct where burnout of combustion gases occurs, and extensive use of
flue gas recirculation (FGR). A complete description of an operating facility
is included in the MWC Retrofit Study.1
3.5.1 Emissions Data
3.5.1.1 Pittsfield. Massachusetts
There are three sets of CDD/CDF data available from modular excess air
MWCs. The first data set includes the parametric test results obtained from a
research program conducted at the Vicon/Enercon facility in Pittsfield, MA.?
A facility equipment schematic is shown in Figure 3-14. The plant comprises
three 120 tpd (109 Mg/day) units and two waste heat boilers. Testing was
performed with two of the three units in operation, which is the normal
operating condition for the facility. Each boiler exhausts to an electrified
granular bed (EGB) filter for removal of PM. The EGBs typically operate at
475°F (246°C). Organic emissions, including CDD/CDF, PCBs. chlorophenols, and
chlorobenzenes. were measured over a large range of operating conditions and
while firing various fuels (MSW. PVC spiked MSW. PVC free waste).
Table 3-15 presents a summary of average CDD/CDF and CO emissions
reported for each operating condition investigated in the parametric test.
The temperature specified for each test condition is measured at the exit of
the secondary combustion chamber. Each test condition consisted of two
individual sampling runs, with the exception of the 1400°F condition, which
3-69
-------
TABLE 3-14. EXISTING MODULAR EXCESS AIR COMBUSTORS
PLANT LOCATION
Mayport Naval Station,
FL
Pittsfield, MA
Pascagoula, MS
Nottingham. NH
Cleburne. TX
Bellingham. WA
Rutland, VT
Pigeon Point, DE
Sitka, AK
St. Croix, WI
Pope County, MN
Franklin, KY
Lewisburg. TN
Frenchville, ME
Readsboro. VT
Stamford. VT
MANUFACTURER
NA
Vicon/Enercon
Sigoure Freres
Combustal 1
Cadoux
NA
Vicon/Enercon
Vicon/Enercon
Sigoure Freres
Cadoux
Cadoux
Cadoux
CICO
01 ivine
Combustal 1
Combustal 1
# OF
UNITS
1
3
2
1
3
1
2
5
2
3
2
2
1
1
1
1
INDIVIDUAL
UNIT SIZE
tpd Mg/day
48 44
120 109
75 68
8 7.3
38 35
100 91
120 109
120 109
25 23
38 35
38 35
38 35
60 55
50 45
NA NA
10 9.1
YEAR OF
START-UP
1978
1981
1985
1972
1986
1986
1987
1987
1985
1987
1987
1987
1980
1982
1973
1973
APCD
Cyclone
EGB
ESP
None
ESP
NA
ESP/
packed tower
ESP
Cyclone/
ESP
DS/FF
ESP
Cyclone
WS/Cyclone
None
None
NA
ESP INLET
TEMPERATURE
op oC
-
-
NA NA
-
450 432
NA
400 204
400 204
450 232
-
415 213
-
-
-
-
NA NA
I
^J
o
-------
CO
I
—I
Ash
Removal
Secondary
Chambers
Tertiary
Duct
Stacks
Recirculated
UF Air
Primary
Combustion Chambers
EGBs
Figure 3-14. Pittsfield, MA Modular Excess Air MWC
-------
TABLE 3-15. PITTSFIELD. MA MODULAR EXCESS AIR MWC
EMISSIONS TEST DATA
TESTING CONDITION
1300°F - MSW
1400°F - MSW
1550°F - MSW
1550°F - MSW + H20
1800°F - MSW
1800°F - MSW. low 02
1800°F - MSW + PVC
1800°F - PVC free
1800°F - PVC free + PVC
1800°F - PVC free + H20
TERTIARY DUCT
CDD/CDF
(ng/dscm)
112
18
15
57
-
76
-
31
14
48
CO
(ppmv)
201
44
9
17
4
7
6
1
6
8
BOILER OUTLET
CDD/CDF
(ng/dscm)
403
40
57
21
94
165
148
71
87
28
CO
(ppmv)
148
22
15
14
12
9
7
9
13
7
STACK
CDD/CDF
(ng/dscm)
-
-
-
-
154
-
261
-
-
-
3-72
-------
included only one run. Sampling for CDD/CDF was performed at the boiler
outlet for each operating condition. COD/CDF stack sampling was performed
during two conditions (1800°F-MSW and 1800°F-MSW and PVC). and CDD/CDF samples
were gathered at the tertiary duct (just upstream of the boiler) during the
eight other conditions. Carbon monoxide emission levels were measured in the
tertiary duct and at the boiler outlet during all runs. Fairly extensive
process monitoring was performed during this test program, including
measurement of airflows and temperatures at various locations in the system.
Testing was performed for the suspected precursors of CDD/CDF (PCBs.
chlorobenzenes. chlorophenols). Continuous monitors were maintained to
measure 02, C02, CO, S02. NOX. HC1 . and THC at various locations in the
system. Control of combustion temperatures was maintained by modulation of
feed rates and recirculated flue gas and, to a lesser extent, fresh airflows.
One of the main conclusions made in the data analysis was that CDD/CDF
emission levels were not generally affected by the different waste character-
istics evaluated in the program. However, as expected, emissions of HC1 were
noticeably affected by PVC content in the waste. In most cases. CDD/CDF
concentrations increased at each sampling location as the flue gases passed
through the system. The temperatures at the tertiary duct sampling location
are nearly equivalent to the target values specified in each sampling
condition. The sampling point was upstream of the flue gas recirculation
injection point (see Figure 3-14). The amount of recirculated (tempering) air
injected into the tertiary duct controls the boiler inlet gas temperature,
which varied from approximately 1100°F (593°C) during the 1300°F-MSW condition
to approximately 1400°F (760°C) during normal operating conditions (1800°F-
MSW). The average boiler outlet gas temperature varied from 460 to 540°F (255
to 282°C). Therefore, the flue gases pass through the critical CDD/CDF
formation temperature, approximately 572°F (300°C), in the boiler. This is
reflected by the increases in CDD/CDF concentrations between the tertiary and
boiler outlet sampling locations. This result was observed during six of the
eight conditions. The formation rate appears to be higher than actually may
be occurring, because the gas stream at the boiler outlet location contains
gases recirculated from ahead of the APCD. Increased concentrations of COD
were measured between the two sampling points during all but two conditions
(1550°F-MSW + H20. and 1800°F-PVC free + H20). The influence of water on the
CDD/CDF formation mechanism must be investigated further in order to draw
conclusions related to this observation at Pittsfield. No PM sampling was
performed during any of the test runs. However, waste moisture content may
3-73
-------
have reduced the amount of PM that was entrained in the fly ash and available
for downstream catalytic reactions to occur. A normal sootblowing cycle was
reportedly performed for the boiler during each 4-hour sampling run. The
facility was reportedly scheduled for an annual maintenance shutdown 2 weeks
after the completion of testing; the condition of the plant was considered
normal during testing (no special maintenance was performed prior to
initiating the program).
Paired runs gathered during normal operating conditions (1800°F-MSW)
provided an average CDD/CDF emission rate of 94 ng/dscm at the boiler outlet
(154 ng/dscm at the stack). At the 1500°F-MSW test condition, the total
CDD/CDF emissions averaged 57 ng/dscm at the boiler outlet (no stack measure-
ments available). As secondary chamber temperatures were decreased to 1300°F
(704°C), the average CDD/CDF emission rate increased to 403 ng/dscm at the
boiler outlet. The low temperature runs were performed for experimental
purposes and are not expected to be encountered during normal operating
conditions.
Stack testing was performed at Pittsfield during two operating
conditions (1800°F-MSW. and 1800°F-MSW + PVC). Concentrations of CDD/CDF
increased by 64 and 76 percent, respectively, from the boiler outlet location
to the stack. Average boiler outlet gas temperatures ranged from 472 to 536°F
(250 to 280°C) during these four sampling runs.
During all the aforementioned testing runs, CO emissions were measured,
and average emission levels at the boiler outlet did not exceed 15 ppnw (4-
hour average) except when operating at 1300°F (704°C), when 148 ppmv was
measured.
The extensive emissions and process data generated at Pittsfield
demonstrate that sufficiently high temperatures and adequate mixing conditions
are present to minimize CDD/CDF and CO emissions at normal operating
conditions. The low emission levels measured at Pittsfield confirm that the
units have good combustion practices in place.
3.5.1.2 Pigeon Point. Delaware
A second data set available for the Vicon/Enercon facility is Pigeon
Point, DE. This plant comprises five 120 tpd (109 Mg/day) units that fire a
3-74
-------
mixture of MSW and RDF. with ESP controls. The compliance test at Pigeon
Point was conducted in two phases. Phase I consisted of HC1. $63. CO, and PM
measurements made in the stack. Particulate testing was also performed at the
ESP inlet location for all four units. Phase II involved stack sampling for
CDD/CDF and heavy metals (Pb. Hg, Be. Ni. As. Cd, Cr).
The three run average uncontrolled PM levels for each of the four flues
tested were 1.03 gr/dscf (2370 mg/dscm). 1.03 gr/dscf (2370 mg/dscm), 0.90
gr/dscf (2070 mg/dscm). and 0.43 gr/dscf (990 mg/dscm).39 one of the flues
discharges gases from two combustors. Average flue gas temperatures entering
the ESP ranged from 393 to 433°F (200 to 223°C). Due to the low particulate
concentrations and the low operating temperature, it is doubtful that
substantial CDD/CDF formation would occur in the ESP.
Three CDD/CDF sampling runs were performed in the stack of unit #2. The
average emissions were reported to be 105 ng/dscm.39 The average stack
temperature was reported to be 374°F (190°C). The CO data included in this
test was measured by ORSAT analysis and was reported to be 0.0 percent by
volume. The CDD/CDF concentrations in the ESP fly ash are also reported for
each sampling run. Very limited process data are available to use in
characterizing the operation of the Pigeon Point facility during testing. The
plant attempts to feed a mixture of 5 pounds RDF per pound of MSW (5 kg RDF
per kg MSW), and it appears that this ratio was maintained during the tests.
Based on the assumption that the combustor design and operation are similar to
that at Pittsfield. it can be concluded that good combustion practices are in
place at Pigeon Point. The measured emission levels from Pigeon Point and
Pittsfield confirm the good performance of the Vicon/Enercon design. The
consistency of the CDD/CDF data with that measured at Pittsfield also
indicates that CDD/CDF emission levels are more dependent on combustion
technology than differences in waste feed characteristics at the two sites.
3.5.1.3 Alexandria. Minnesota
A third data set is available from a facility using the Cadoux design.
Emissions testing was performed at the Pope/Douglas Waste-to-Energy Facility
in Alexandria. MN in July 1987. This plant began operating in May 1987 using
two 38 tpd (35 Mg/day) Cadoux modular excess air combustors. Both units are
equipped with an ESP. Average CDD/CDF emissions at the stack were reported to
be 446 ng/dscm.40 The continuous monitoring results indicated that average CO
3-75
-------
emissions were 24 ppmv (1-hour average). The average flue gas temperature at
the ESP inlet sampling location ranged from 490 to 503°F (254 to 262°C).
These values are in the temperature window where CDD/CDF formation has been
observed. Therefore, it is assumed that CDD/CDF at the ESP inlet was lower
than the concentrations in the stack. The CDD/CDF and CO measurements were
made on Unit #2. Particulate sampling was also performed in the stack of both
units.
Thermocouples were installed in Unit #1 at two locations in the primary
combustion chamber. The first was located on the side wall at the grate
level, and the second was in the top of the chamber. The average temperature
at the grate varied from 1300 to 1650°F (704 to 899°C) and the temperature in
the upper furnace ranged from 1770 to 1990°F (965 to 1088°C). Charge rates
were measured during the testing program and both units were operating between
100 and 145 percent rated capacity. Oxygen levels were also measured in an
eight-point traverse at the combustor outlet, and average concentrations were
14.8 percent at Unit #1 and 12.8 percent at Unit #2. These values equate to
approximately 245 percent and 160 percent excess air, respectively.
3.5.2 Baseline Emissions Estimates
Baseline emissions for the model plant are established using the two
Vicon/Enercon MWCs at Pittsfield and Pigeon Point. The emissions data from
these systems and the Cadoux facility at Pope/Douglas County are plotted
together in Figure 3-15. The off-spec, low-temperature runs from the
Pittsfield parametric study are not included in the baseline determination.
Baseline emissions are assumed to be 200 ng/dscm CDD/CDF and 50 ppmv CO. APCD
inlet PM emissions are assumed to be 2 gr/dscf, which is an average value for
mass burn systems.
3.5.3 Combustion Modifications
The model plant was judged to have all the necessary features of good
combustion practice. Therefore, no combustion modifications were required.
3.6 O'Connor Rotary Waterwall MWCs
As shown in Table 3-16, there are three existing MWCs using the O'Connor
Rotary Waterwall design. The Gallatin. TN plant commenced operation in
3-76
-------
o
E
LL
a
o
o
Q
O
600
500 -
400-
300-
200
-*•
8
i
Baseline
• Individual Run
B Average
I
I
§
c ~
|l
!-?
l
8.
o
Q.
Pitlsfield - Boiler Outlet Pittsfield Stack (ESP)
Stack (EGB)
Figure 3-15. Mass Burn Modular Excess Air Baseline Determination
-------
TABLE 3-16. EXISTING ROTARY WATERWALL COMBUSTORS
Plant location
Stoker manufacturer
Boiler manufacturer
Number of units
Unit size (tpd)
Unit size (Mg/day)
Year of start-up
APCD
ESP inlet
temperature (°F)
Gallatin, TN
O'Connor
Keeler
2
100
91
1981/82
Cyclone/ESP
390
199
Bay County. FL
O'Connor
Deltak
2
255
232
1987
ESP
400
204
Dutchess County, NY
O'Connor
Deltak
2
253
230
1987
Cyclone/DI/FF
~
3-78
-------
December 1981 using two 100 tpd (91 Mg/day) combustors. Gallatin was
originally equipped with a cyclone and an electrostatically enhanced baghouse,
but the fabric filter collector, which experienced numerous operating
problems, was replaced by an ESP in 1983. Westinghouse purchased O'Connor in
1986. and started up the Bay County. FL plant in 1987. Bay County comprises
two combustors. each with a rated capacity of 255 tpd (232 Mg/day). Wood
waste is currently co-fired with MSW at Bay County. Electrostatic
precipitators are used for emission control. A third O'Connor plant located
in Dutchess County. NY. commenced operation in 1987. using two 253 tpd (230
Mg/day) combustors equipped with a cyclone, dry sorbent injection, and a
baghouse.
3.6.1 Emissions Data
There are currently no published data available to estimate baseline
CDD/CDF emission levels. Testing has been performed at Bay County, but
results have not yet been published. Some limited test data are reported for
the Gallatin plant and for an O'Connor facility in Kure, Japan. Particulate
emissions at the APCD inlet were reported to be 3.08 gr/dscf (7080 mg/dscm)
and 2.36 gr/dscf (5430 mg/dscm). respectively, from these two plants.23 in
addition, CO data were gathered at Gallatin and the average emissions were
reported to be 545 ppmv. In a meeting with EPA. Westinghouse reported that
the Bay County plant has been able to achieve CO emissions less than 100 ppmv
as a result of recent modifications made to combustion air distributions.41
3.6.2 Baseline Emissions Estimates
Table 3-17 presents an assessment of the performance of the Bay County
MWC relative to recommended good combustion practices for rotary waterwall
combustors. An engineering evaluation of the facility design led to
conclusions that the existing tertiary (overfire) air nozzles above the
discharge of the rotary section do not provide sufficient penetration and
coverage of the boiler cross section. As a result, mixing of combustion
products with oxygen is not optimized and CDD/CDF emissions are estimated to
be relatively high. Due to a lack of available data to establish a CDD/CDF
emission value, it was assumed that the emission levels were similar to those
of the small mass burn waterwall model plant and the RDF fired model plants.
The baseline CDD/CDF emissions were assumed to be 2000 ng/dscm. Based on
information provided by Westinghouse, there is evidence that 100 ppmv CO can
3-79
-------
TABLE 3-17. MASS BURN ROTARY WATERWALL MWCS - PERFORMANCE ASSESSMENT
FACILITY
NUMBER OF UNITS - FGC
UNIT SIZE, tpd (Mg/day)
UNCONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
PM (mg/dscm)
CONTROLLED EMISSIONS
CDD/CDF (ng/dscm)
CO (ppmv)
COMBUSTION PARAMETERS
GOOD COMBUSTION
PRACTICE RECOMMENDATIONS
Bay County, FL
2 - ESP
255 (232)
Not Available (NA)
NA
NA
<100
FACILITY DESIGN
AND OPERATING CONDITIONS
DESIGN
Temperature at fully
mixed location
Underfire air
Overfire air capacity
Tertiary air design
Auxiliary fuel capacity
Exit gas temperature
OPERATION
Excess air
Turndown
Tertiary air
Start-up procedures
Auxiliary fuel use
VERIFICATION
02 levels
CO
Temperature
Air distribution
Exit gas temperature
1800°F (982°C) average
4 plenums, including
one at burnout grate
Sum of secondary and
tertiary air designed to
supply 40% of total air
Complete coverage and
penetration
As required to achieve
temperature limits
during start-up
<450°F (232°C) at PM
control device inlet
3-9% 02 in flue gas (dry)
80-110% design load
Complete coverage and
penetration
Auxiliary fuel to
design temperature
High CO. low temp:
start-up/shutdown
Monitor
Monitor «100 ppm at 7% 02)
Monitor
Monitor
Monitor
3-80
1400°F (760°C) at inlet
to convective section
4 plenums (one at
afterburning grate)
Confident!' al
Confident!' al
Oil - 40% load
450°F (232°C)
5-57% 02 (wet)
30% minimum
Not achieved
Use steam preheat from
adjacent combustor
NA
Yes
Yes
Yes
UF, OF, tertiary
Yes
-------
be achieved. Therefore, this value is assumed as a baseline emission level.
Lastly, it was assumed that inlet particulate emission levels are typical of
mass burn waterwall MWCs. Therefore. 2 gr/dscf (4600 mg/dscm) was assumed as
a baseline value.
3.6.3 Emission Reductions Resulting From Combustion Modifications
The only modification made to the model plant is a redesign of the
tertiary (overfire) air nozzles to improve mixing. Estimated emission
reductions result in CDD/CDF emissions of 400 ng/dscm. The basis for this
estimate is engineering judgment. No reduction in CO or PM emissions is
assumed.
3-81
-------
4.0 REFERENCES
1. "Municipal Waste Combustors - Background for Proposed Guidelines for
Existing Facilities." EPA-450/3-89-27e. August 1989.
2. Assessment of Municipal Waste Combustor Emissions Under the Clean Air
Act. U.S. EPA Advance Notice of Proposed Rulemaking, 52 FR 25399. July
7. 1987.
3. "Municipal Waste Combustors: Background Information for Proposed
Standards: Post Combustion Technology Performance." EPA-450/3-89-27C.
August 1989.
4. "Municipal Waste Combustion Study: Report to Congress." EPA/530-SW-87-
021a. May 1987.
5. "Municipal Waste Combustion Study: Combustion Control of MSW Combustors
to Minimize Emission of Trace Organics." EPA/530-SW-87-021c. May 1987.
6. Environment Canada. National Incinerator Testing and Evaluation
Program. "Two Stage Combustion." Summary Report. EPS 3/UP/l.
September 1986.
7. New York State Energy Research and Development Authority. "Results of
the Combustion and Emissions Research Project at the Vicon Incinerator
Facility in Pittsfield. MA." June 1987.
8. Radian Corporation. "Municipal Waste Combustion Multipol1utant Study -
Summary Report." North Andover RESCO. North Andover, MA. EMB Report
No. 86-MIN-02a. March 1988.
9. Entropy Environmentalists. "Stationary Source Sampling Report -
Pinellas County Resource Recovery Facility." St. Petersburg. FL.
February and March 1987.
10. Stieglitz. Vogg. "New Aspects of PCDD/PCDF Formation in Incinerator
Processes." Presented at NITEP Conference on Municipal Waste
Incineration. Montreal, Quebec. October 1-2, 1987.
11. Hagenmaier. et al. "Catalytic Effects of Fly Ash from Waste
Incineration Facilities on the Formation and Decomposition of
Polychlorinated Dibenzo-p-dioxins and Polychlorinated Dibenzofurans."
Environmental Science and Technology. November 11, 1987, Vol. 21. 1080-
1084.
12. New York State Energy Research and Development Authority. "Results from
the Analysis of MSW Incinerator Testing at Peekskill, NY." DCN:88-233-
012-21. August 1988.
13. "Municipal Waste Combustors - Background Information for Proposed
Guidelines for Existing Facilities: Cost Procedures." EPA-450/3-89-
27a. July 1989.
14. Entropy Environmentalists. "Municipal Waste Combustion Multipollutant
Study: Emission Test Report - Wheelabrator Millbury. Inc. Millbury,
MA." EMB Report No. 88-MIN-07. July 1988.
4-1
-------
15. New York DEC. "Phase I Resource Recovery Facility Emission
Characterization Study - Overview Report." May 1987.
16. Radian Corporation. "Final Emissions Test Report - Dioxins/Furans and
Total Organic Chlorides Emissions Testing." Saugus Resource Recovery
Facility. Saugus. MA. October 2, 1986.
17. Wheless, E. "Air Emission Testing at the Commerce Refuse to Energy
Facility." Presented at NITEP Conference on Municipal Waste
Incineration. Montreal, Quebec. October 1-2. 1987.
18. Radian Corporation. "Emission Test Report - Marion County Solid Waste-
to-Energy Facility." Brooks. Oregon. EMB Report No. 86-MIN-03.
September 1987.
19. "Emissions Test Results for the PCDD/PCDF Internal Standards Recovery
Study Field Test; Runs 1. 2, 3. 4. 5. 13, and 14." Memorandum from
Michael A. Vancil, Radian Corporation, to C.E. Riley. EPA. July 24.
1987.
20. Ogden Martin. "Environmental Test Report - Alexandria/Arlington
Resource Recovery Facility Units 1. 2, and 3." March 9, 1988
21. Ogden Martin. "Environmental Test Report - Walter B. Hall Resource
Recovery Facility. Tulsa. OK." October 1986.
22. Midwest Research Institute. "Comprehensive Assessment of the Specific
Compounds Present in Combustion Processes. Volume I - Pilot Study of
Combustion Emissions Variability." EPA/OPTS. EPA-560/5-83-004. June
1983.
23. "Municipal Waste Combustion Study: Emissions Data Base for MWCs."
EPA/530-SW-87-021b. May 1987.
24. Energy Systems Associates. "Air Emissions Tests at the Hampton Refuse-
Fired Steam Generating Facility." June 1988.
25. Scott Environmental Services. "Sampling and Analysis of Chlorinated
Emissions from the Hampton Waste-to-Energy System." Prepared for the
Bionetics Corporation. May 1985.
26. Schindler, P. Energy and Environmental Research Corporation. "Site
Visit Report Summary - Hampton, VA Steam Plant." Submitted to U.S. EPA
on December 22. 1988.
27. Entropy Environmentalists. "Stationary Source Sampling Report - Signal
Environmental Systems, Inc. Claremont Facility, Claremont, NH." No.
5533-A. June 1987.
28. Environment Canada. NITEP. "Environmental Characterization of Mass
Burning Incinerator Technology at Quebec City." Summary Report. EPS
3/UP/5. June 1988.
29. Environment Canada. NITEP. "Air Pollution Control Technology."
Summary Report. EPS 3/UP/2. September 1986.
4-2
-------
30. Midwest Research Institute. "Emissions Test Report - Occidental
Chemical Corporation Energy from Waste Facility. Niagara Falls, NY."
April 11. 1988.
31. Radian Corporation. "Emissions Test Report - Refuse Fuels Associates."
Lawrence, MA. June 3. 1987.
32. Entropy Environmentalists. "Stationary Source Sampling Report -
Lawrence, MA Thermal Conversion Facility." September 2-4. 1987.
33. "Municipal Waste Combustion Multi-Pol 1utant Study. Emission Test
Report. Maine Energy Recovery Company Refuse-Derived-Fuel Facility,
Biddeford. ME." EPA-600/8-89-064a. July 1989.
34. Barsin, J.A.. Bloomer, T.M.. Gonyeau, J.A., and P.K. Graika. "Initial
Operating Results of Coal-Fired Steam Generators Converted to 100%
Refuse-Derived-Fuel." Presented at the American Flame Research
Committee 1987 International Symposium of Hazardous, Municipal, and
Other Wastes. Palm Springs, CA. November 2-4. 1987.
35. Interpoll Laboratories. "NSP Red Wing RDF plant - Results of March 1988
Compliance Test on Boiler No. 2." May 10. 1988.
36. Midwest Research Institute. "Emissions Test Report - City of
Philadelphia NW and EC Municipal Incinerators." October 31. 1985.
37. Roy F. Weston, Inc. "City of Philadelphia Northwest Incinerator -
Source Emissions Compliance Test Report." February 1988.
38. Cal Recovery Systems. "Final Report: Evaluation of Municipal Solid
Waste Incineration." January 1987.
39. Roy F. Weston. Inc. "Compliance Test Results - Pigeon Point. DE Energy
Generating Facility." January 1988.
40. Results of Non-Criteria Pollutant Testing Performed at Pope-Douglas
Waste to Energy Facility. July 1987. Response to Section 114
Information Questionnaire provided to EPA on May 16, 1989.
41. Radian Corporation. Minutes from December 10, 1987 meeting between
Westinghouse. EPA. EER. and Radian Corporation.
4-3
-------
REPORT DATA
o** itif ttifrif t>f fsi
M f I O *J T », <
.__EPA-_600/8-89-0_58
'I'll / A. ( • , . - • •• I
Municipal Waste Combustion Assessment: Combustion
Control at Existing Facilities
P.J. Schindler
August 1989
>-.•.. •"•-"7^,.-*"-/N ,,,
lie
" t «. I MI »• '
Energy and Environmental Research Corporation
3622 Lyckan Parkway, Suite 5006
Durham. NC 27707
M t Hff. TiCff-r-it NC
68-03-3365
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Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
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Project Officer - James D. Kilgroe
The EPA's Office of Air Quality Planning and Standards (OAQPS) is
developing emission standards and guidelines for new and existing MWCs under
the authority of sections lll(b) and lll(d) of the Clean Air Act (CAA). The
EPA's Office of Research and Development (ORD) is responsible for developing
the technical basis for good combustion practice (GCP), which is included as a
regulatory alternative in the standards and guidelines. This report provides
the supporting data and rationale used to establish baseline emission levels
for model plants that represent portions of the existing population of MWCs.
The baseline emissions were developed using the existing MWC data base, or, in
cases where no data existed, engineering judgement. The baseline emissions
represent performance levels against which the effectiveness and costs of
emission control alternatives can be evaluated. An assessment of potential
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emission reduction estimates were made for each retrofit application. This
report provides the rationale used to estimate the emission reductions
associated with each combustion retrofit.
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