EPA/600/R-94/145
September 1994
EVALUATION OF OXYGEN-ENRICHED MSW/SEWAGE SLUDGE
CO-INCINERATION DEMONSTRATION PROGRAM
by
and
The Solid Waste Association of North America
Silver Spring, Maryland 20910
Cooperative Agreement No. 818238
Project Officer
Lynnann Hitchens
Waste Minimization, Destruction, and Disposal Research Division
Risk Reduction Engineering Laboratory
Cincinnati, Ohio 45268
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
Printed on Recycled Paper
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DISCLAIMER
The information in the document has been funded wholly or in part by the
United States Environmental Protection agency under assistance agreement CR-
818238 to the Solid Waste Association of North America (SWANA). It has been
subject to the Agency's peer and administrative review and has been approved for
publication as an EPA document. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
11
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FOREWORD
Today's rapidly developing and changing technologies and industrial
products and practices frequently carry with them the increased generation of
materials that, if improperly dealt with, can threaten both public health and the
environment. The U.S. Environmental Protection Agency is charged by Congress
with protecting the Nation's land, air, and water resources. Under a mandate of
national environmental laws, the agency strives to formulate and implement
actions leading to a compatible balance between human activities and the ability
of natural systems to support and nurture life. These laws direct the EPA to
perform research to define our environmental problems, measure the impacts, and
search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning,
implementing, and managing research, development, and demonstration programs to
provide an authoritative, defensible engineering basis in support of the
policies, programs, and regulations of the EPA with respect to drinking water,
wastewater, pesticides, toxic substances, solid and hazardous wastes, and
Superfund-related activities. This publication is one of the products of that
research and provides a vital communication link between the researcher and the
user community.
This publication is part of a series of publications for the Municipal
Solid Waste Innovative Technology Evaluation (MITE) Program. The purpose of the
MITE program is to: 1) accelerate the commercialization and development of
innovative technologies for solid waste management and recycling, and 2) provide
objective information on developing technologies to solid waste managers, the
public sector, and the waste management industry.
E. Timothy Oppelt
Risk Reduction Engineering Laboratory
111
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ABSTRACT
This report provides an evaluation of a two-phased demonstration program
conducted for the U.S. Environmental Protection Agency's Municipal Solid Waste
Innovative Technology Evaluation Program, and the results thereof, of a recently
developed method of sewage sludge management. This method, known as "oxygen-
enriched co-incineration," is intended to allow the co-combustion of dewatered
sewage sludge with municipal solid waste in a waste-to-energy facility without
affecting solid waste throughput capacity or facility operational
characteristics.
The report describes the demonstration program plan and the tests
performed; assesses the execution of the demonstration program; provides the
reported test results; and presents the results of an independent verification
of the test results. Also evaluated in this report are the
technical/operational, environmental regulatory/permitting, and economic
implications of the commercial application of oxygen-enriched co-incineration.
Finally, overall conclusions and recommendations are provided based on the
evaluation.
This report was submitted in partial fulfillment of Cooperative Agreement
818238 under the partial sponsorship of the U.S. Environmental Protection Agency.
This report covers a period from October 4, 1991, to April 19, 1992.
IV
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CONTENTS
Disclaimer ii
Foreword i i i
Abstract i v
Figures vi
Tables vii
Acknowl edgements vi i i
1. Introduction 1
Program Eva! uated 1
Conclusions and Recommendations 1
2. Demonstration Program Description 3
Program Objectives 3
Pilot Facility Description 3
Demonstration Program Plan 5
Pilot Facility Modifications 5
3. Program Execution 10
Fuel Utilized 10
Tests Performed 10
Problems Encountered 12
Data Acquisition System 13
Data Production 17
4. Program Results 19
Data Reduction 19
Independent Verification of Test Results 37
5. Commercial Application Considerations 43
Technical and Operational Implications 43
Environmental Regulatory and Permitting Regulations 45
Economic Implications 52
6. Summary of EVALUATION 59
Conclusions and Recommendations 59
Appendices are not included in this document. Limited quantities are available
from Lynnann Hitchens, U.S. EPA Center Hill Research Facility, 5995 Center Hill
Road, Cincinnati, OH 45224.
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FIGURES
Number paqe
1. Process Flow Diagram - Riley Pilot MSW Combustion Facility 4
2. Riley Instrumentation and Sampling Points 15
3. Schematic Representation of Heat and Material Balances 20
4A. MSW Throughput As a Function of Oxygen Flow (metric) 23
4B. MSW Throughput As a Function of Oxygen Flow (U.S. units) 24
5A. Cumulative MSW and Sludge Processing Capacity (metric) 25
5B. Cumulative MSW and Sludge Processing Capacity (U.S. units) 26
6A. Cumulative MSW and Sludge Processing Capacity (metric) 28
6B. Cumulative MSW and Sludge Processing Capacity (U.S. units) 29
7A. Oxygen Usage for MSW and Sewage Sludge Coincineration (metric) 32
7B. Oxygen Usage for MSW and Sewage Sludge Coincineration (U.S. units) 33
8. Hydrochloric Acid Emissions 36
8A. Flue Gas Hydrocarbon Emission Trend (Run 26B) 38
VI
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TABLES
Number Page
1. Planned Pilot Test Schedule 6-7
2. Description of Tests 8
3. Test Runs Actually Performed 11
4. Data Acquired 14
5. Eliminated Test Runs 16
6. Completed Test Runs 13
7. MSW Throughput As a Function of Oxygen Addition 22
8. Normalized Pilot Plant Data 27
9. Pilot Test Flue Gas Emissions Summary 30
10. Bottom Ash/Fly Ash Summary - Phase I/Phase II 34-35
11A. Phase I - Comparison of Corrected APCI Results to Theoretical
Results (metric) 39
11B. Phase I - Comparison of Corrected APCI Results to Theoretical
Results (U.S. units) 40
12A. Phase II - Comparison of Corrected APCI Results to Theoretical
Results (metric) 41
12B. Phase II - Comparison of Corrected APCI Results to Theoretical
Results (U.S. units) 42
13. Existing and Expected Section III(d) Emission Guidelines
Applicable to Existing Municipal Waste Combustors 48
14. Existing and Expected New Source Performance Standards
Applicable to New Municipal Waste Combustors 51
15. Cases Evaluated 53
16. Estimated Facility-Retrofit Capital Costs 53
17. Estimated Oxygen-Production Facility Capital Costs 54
18. Retrofitted Facility Estimated Additional Operating and
Maintenance Costs 55
19. Estimated Additional Oxygen-Production Facility Operation
and Maintenance Costs 56
20. Sludge Treatment and Disposal Costs 57
Vll
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ACKNOWLEDGEMENTS
This report was prepared under the coordination of Lynnann Hitchens, U.S.
Environmental Protection Agency (EPA) Municipal Solid Waste Innovative Technology
(MITE) Program Project Manager at the Risk Reduction Engineering Laboratory,
Cincinnati, Ohio, and Andy Miller of the Air & Energy Engineering Research
Laboratory, Research Triangle Park, North Carolina. Contributors to and
reviewers of this report include Charlotte Frola of the Solid Waste Association
of North America (SWANA).
This report was prepared for EPA's MITE program by Richard D. Larson, Shawn
Worster, Jan Sotan, and others of CSI Resource Systems, Incorporated.
FPA fnl!LDe?!!rtmenti of Ener9* (°OE) funded the demonstration of this technology.
P^lltln t t evaluatjon at ^e pilot plant. This report contains mostly
evaluation test information. Additional details on the technology can be found
iron /ehPOri'- °x^en-E"riched Coincineration of MSW and Sewage Sludge,"
E^L^rn ,Pr°idU,CtS and Chemicals for the National Renewable Energy
Laboratory NREL) (a laboratory of the DOE), Golden, Colorado under Contract No
VI 1 1
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SECTION 1
INTRODUCTION
PROGRAM EVALUATED
In the past, sludge management planning has typically provided for a single
method of reuse or disposal, such as landfill ing. More recently, given stricter
regulation of the disposal of sewage sludge in landfills and the banning of ocean
dumping, the wastewater treatment industry has begun to recognize the need for
multiple disposal and/or beneficial reuse options.
In the interest of providing an efficient sludge management option, Air
Products and Chemicals, Inc. (APCI), has developed a concept known as "oxygen-
enriched co-incineration." This technology is designed for use as a retrofit
technology for existing waste-to-energy facilities. It utilizes a unique sludge
injection system to feed sludge, that along with oxygen enrichment, provides for
co-incineration, without sacrificing MSW capacity. Under Contract #ZF-1-11115-1,
awarded by the Department of Energy, APCI developed a two-phased "pilot scale"
demonstration program to demonstrate and optimize, to the extent possible, this
co-incineration process. The program was concurrently selected by the MITE
program for evaluation.
In the demonstration of their technology APCI had several objectives. The
foremost of which was to demonstrate the mechanical feasibility of their
technology by evaluating a variety of sludge feed and sludge distribution methods
to optimize sludge combustibility. APCI also sought to determine the optimum
ratio of oxygen to sludge for MSW and sludge co-incineration and to determine the
effect of oxygen-enriched co-incineration on flue gas emissions and residual
bottom and fly ashes.
The goal of the MITE evaluation was to verify the results of the pilot-
scale testing, including the comparison of measured results with theoretical
combustion calculations, formulate cost information for various retrofit
scenarios, and consider the technical and operational implications of commercial
application and scale-up.
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
The following conclusions and recommendations are made pursuant to the evaluation:
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Technical issues requiring further evaluation prior to commercial
application of APCI's oxygen-enriched co-incineration technology include:
confirmation of the long-term reliability of the
proprietary sludge-feed system;
determination of the long-term impacts of introducing of
sludge, oxygen, and moisture into existing waste-to-
energy units relative to fouling, corrosion,
performance, availability, and air pollution control
equipment, including the potential need to add
additional control technology or modify existing
controls;
determination of the effect that introduction of high-
moisture sludge and oxygen into the combustion
environment will have on organic pollution emissions;
and
confirmation of expected oxygen consumption per dry ton
of sludge to a range consistent with the need to
properly size and economically evaluate the oxygen
production requirements.
Based on conservative budgetary capital and operating costs, oxygen-
enriched co-incineration of municipal sewage sludge in existing waste-to-
energy facilities appears competitive, on a per-dry-ton basis, with
alternative sludge treatment and disposal approaches, and therefore
warrants further examination.
The limited pilot test program indicates that sludge was co-incinerated
with MSW up to a maximum ratio of 11.3 percent dry sludge per pound of MSW
with the injection of 3.5 to 5.5 kilograms (pounds) of oxygen per kilogram
(pound) of sludge while maintaining relatively constant MSW feed rates
- 2 -
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SECTION 2
DEMONSTRATION PROGRAM DESCRIPTION
PROGRAM OBJECTIVES
The specific objectives of APCI's demonstration program were to, primarily:
• determine the maximum ratio of dewatered sludge to MSW that can be
co-incinerated with oxygen-enriched air;
and, in addition, to:
• evaluate a variety of sludge-feed and sludge-distribution methods to
determine those that would optimize sludge combustibility;
• determine the effect of oxygen-enriched co-incineration on flue gas
emissions and residual bottom and fly ashes;
• determine the most advantageous ratio of oxygen to sludge for MSW
and sludge co-incineration; and
• evaluate the effect of oxygen-enriched combustion air on the MSW
combustion rate during both MSW combustion alone and MSW/sludge co-
incineration.
The demonstration program was conducted in two phases: Phase I took place
in January and February of 1992, and Phase II took place in September 1992.
PILOT FACILITY DESCRIPTION
The pilot facility utilized in the demonstration program (see Figure 1) is
owned and operated by Riley Stoker Corporation and is located at its Worcester,
Massachusetts, research and development facility.
The pilot unit is a prototype of a full-scale Takuma system for mass-
burning MSW. It is sized to burn a nominal 204 kilograms per hour (450 pounds
per hour) of MSW, is 17 feet, 10 inches high and 11 feet, 9 inches long, and
includes a reciprocating-grate stoker. The furnace is refractory lined and
water-cooled by jacket sections to simulate a waste-heat boiler. Flue gas
exiting the furnace is cooled prior to entering the baghouse and scrubber, and
operating parameters are monitored by a computerized data acquisition system.
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Monitoring of NOX, 02, CO, C02, S02, and total hydrocarbons is provided by
a continuous emissions monitoring system (CEMS) located prior to the air
pollution control equipment. During Phase I, a separate HC1 monitoring system
was installed to monitor HC1. Combustion air and induced draft fans to remove
flue gas are controlled by dampers. Provisions are provided for collecting both
bottom and fly ash.
DEMONSTRATION PROGRAM PLAN
Planned Tests and Testing Schedule
Table 1 provides a list of the planned demonstration tests for both the
Phase I and Phase II portions of the demonstration program. Table 2 provides
descriptions of these tests.
Phase I of the program was intended to test the effects of oxygen-enriched
combustion air on the combustion of, first, MSW alone, and then on MSW/sludge co-
incineration. Phase II was intended to determine the optimal ratio of oxygen to
sludge during co-incineration (including testing co-incineration with no oxygen
enrichment), and the optimal ratio of MSW to sludge. During both phases, the
parameters of MSW combustion alone were used as a baseline for all other
measurements.
Quality Assurance/Quality Control Manual and Documentation
Using "Preparation Aids for the Development of Category III Quality
Assurance Project Plans," EPA/600/8-91/005, published in February 1991, CSI
developed a Quality Assurance/Quality Control (QA/QC) manual to ensure that the
project needs would be met and that quality control procedures would be followed
during testing sufficient to obtain data in a prescribed, consistent manner. In
addition, modifications to the QA/QC manual were prepared by CSI in response to
the modifications made to the Phase II test program by APCI, which focused
primarily on the co-incineration of MSW and sewage sludge with oxygen enrichment.
Appendix A to this report includes copies of the QA/QC manual and Appendix
E to the QA/QC manual.
PILOT FACILITY MODIFICATIONS
Prior to commencement of the demonstration tests, the following
modifications were made to the pilot facility:
• An additional sludge-feed system was constructed to permit the
introduction of sludge by using either an extrusion plate or an air-
aspirated injection system. In both cases, sludge was delivered
with a positive-displacement pump.
• An oxygen-enrichment control system was added to introduce oxygen
during the combustion process to the overfire air and/or underfire
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TABLE 1. PLANNED PILOT TEST SCHEDULE
PHASE I:
WEEK 1
Day 1
Day 3
WEEK 2
Day 1
Day 2
Day 2
WEEK 3
Day 1
Day 2
Day 3
WEEK 4
Day 1
Day 2
Day 3
WEEK 5
Day 1
Day 2
Day 3
PHASE II
WEEK 1
Day 1
Day 2
Day 3
TEST DESCRIPTION
Startup/Shakedown
Baseline
02-Enriched MSW Incineration
02-Enriched MSW Incineration
02-Enriched MSW Incineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
02-Enriched Coincineration
Startup/Shakedown
Coincineration w/o 02
Enrichment
Coincineration w/o 02
Enrichment
Ml & M2
M3 & M4
M5 & open
Cl
C2
open
C3
C4
open
C5
C6
open
CC1
CC2
% SOLIDS NO. OF RUNS
SLUDGE
2
2
2
2
2
20% 3
20% 3
3
20% 3
25% 3
3
25% 3
25% 3
3
20% 2
20% 2
(continued)
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TABLE 1. (continued)
TEST DESCRIPTION % SOLIDS NO. OF RUNS
SLUDGE
PHASE II (continued)
WEEK 2
Day 1 02-Enriched Coincineration C7 20% 2
Day 2 02-Enriched Coincineration C7 & C8 20% 2
Day 3 02-Enriched Coincineration C8 2
WEEK 3
Day 1 02-Enriched Coincineration C9 20% 2
Day 2 Open 20% 2
Day 3 Open 20% 2
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air (combustion and burnout zones) and to the air-aspirated
injection system.
An HC1 monitoring system was added to assess the impact of co-
incineration on HC1 emission rates. This was included only during
Phase I testing.
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SECTION 3
PROGRAM EXECUTION
FUEL UTILIZED
Processed MSW was procured and was used during the entire test program
The waste was characteristic of raw MSW; however, it had been shredded to a size
of 15.2 centimeters (6 inches), with 50 to 60 percent of ferrous metals having
been removed. It was necessary to utilize this processed MSW in order to comply
with the 15.2-centimeter (6-inch) maximum particle size limitation of the pilot
unit. The MSW was periodically sampled to develop ultimate and proximate
analyses, which were compared with the results produced from the heat and
?? uiu1 balance Program. During each test run, samples were taken to determine
the MSW moisture content.
Sewage sludge with a solids-content range of 22 to 25 percent was obtained
from local wastewater treatment facilities. The material had been ground for
Phase I testing, however, it was not ground for Phase II testing APCI added
water manually to the sludge to reduce its solids content to approximately 15
percent, which provided for better sludge pump performance. The sludge was
periodically sampled and analyzed to determine its proximate/ultimate analysis
and moisture content.
TESTS PERFORMED
Table 3 lists the test runs actually performed during Phase I and Phase II
testing. The following tests, although proposed in the initial demonstration
program plan, were not performed; their deletion constitutes the sole deviation
from the demonstration program outlined in the QA/QC manual:
• Test M4 - Oxygen was to be added to the air supplying the burnout
grate so as to reduce combustible loss. However, given that minimal
combustible loss occurred while oxygen-enriched air was being
supplied to the combustion zone, no benefit would have been obtained
from this test.
• Tests C4, C5, and C6 - These tests reguired sludge with a 25-percent
solids content to be fed to the pilot unit. However, in order to
obtain adeguate pump performance, the sludge solids content had to
be maintained at less than 20 percent.
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TABLE 3. TEST RUNS ACTUALLY PERFORMED
PHASE I:
Weekl
20- Jan
21-Jan
22- Jan
23- Jan
Week 2
27- Jan
28 -Jan
29- Jan
30- Jan
Week 3
10-Feb
11-Feb
12-Feb
13-Feb
14-Feb
Week 4
19-Feb
21-Feb
WeekS
26-Feb
27-Feb
PHASE II
Weekl
2-Sep
3-Sep
4-Sep
Week 2
14-Sep
15-Sep
16-Sep
17-Sep
TEST DESCRIPTION
Shakedown
Shakedown
Baseline
Baseline
Shakedown
Shakedown
Baseline/02 Enriched MSW Incineration
Baseline/Coincineration
O2 Enriched MSW Incineration
O2 Enriched Coincineration
O2 Enriched Coincineration
O2 Enriched Coincineration
Baseline/02 Enriched MSW Incineration
Baseline/02 Enriched MSW Incineration
Shakedown
O2 Enriched Coincineration
O2 Enriched Coincineration
Baseline
Baseline
Baseline/Coincineration/O2 Enriched Coincineration
Baseline/02 Enriched Coincineration
Baseline/02 Enriched Coincineration
Baseline/02 Enriched Coincineration
Coincineration
SLUDGE FEED
SYSTEM
Sludge Pump
Sludge Pump
Sludge Pump
Sludge Pump
Atomization Nozzle
Atomization Nozzle
Atomization Nozzle
Atomization Nozzle
Atomization Nozzle
Atomization Nozzle
Atomization Nozzle
RUN NO.
3A/3B
4A/4B
7A, B, C
8A, B
9A
10A, B
11A
12A, B
13A, B, C
14A, B, C
16A, B, C
17A, B, C
20
21
22,A, B, C
23A, B, C
24A, B, C
25B, C
26B
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Flue gas emissions were continuously monitored for 0?, C09, CO NO SO
and total hydrocarbons during Phase I and Phase II testing. HC1 emissions' were
monitored during Phase I testing only. The emissions were measured prior to the
air pollution control system and provided information relative to the impact of
co-incineration on flue gas emissions prior to the air pollution control system
Bottom and fly ash were analyzed to assess the impact co-incineration would have
on the heavy metal content of the residual ash.
PROBLEMS ENCOUNTERED
As is to be expected in any pilot program, certain problems were
encountered during the demonstration test which impeded the collection of data
These problems were:
• MSW pluggage of the feed chute. As previously stated, the MSW was
a shredded fuel with approximately 50 to 60 percent of ferrous
material removed. However, due to the presence of a significant
amount of large-sized ferrous and non-ferrous metals, bridging
occurred in the feed chute, which interrupted flow, to the pilot
plant and resulted in combustion temperature drops and a
commensurate rise in CO production.
• Broken reciprocating-grate rods, which before being replaced
required the unit to be shut down and cooled off.
• Corrosion of the flue gas sampling probe, which resulted in
unsuccessful runs due to poor-quality data.
These problems, although nuisances, were not the results of problems with
the technology being tested. However, the following problem was considered to
have been related to the technology development.
The initial sludge-feed system, in place during Phase I of the
demonstration program, included an extrusion plate that fed a consistent rate of
sludge to the top of the refuse bed. The extrusion plate consisted of a series
of holes .32 to 1.27 centimeters (1/8 to 1/2 inches) in diameter and was fixed
in place. The slow grate speed, however, allowed the sludge to puddle-
consequently, a minimum amount of sludge was combusted. '
The orifice plate holes also continuously plugged, further confounding the
effort. The system was modified to enable sludge to be spread manually by hose
in the feed hopper and manually by shovel over the MSW as it was being fed into
the in-feed conveyor. However, these approaches also proved unsuccessful.
During the latter part of Phase I testing, APCI acquired a proprietary air-
aspirated nozzle, which was installed and functioned satisfactorily. The nozzle
introduced the sludge to the pilot unit in small enough particle sizes to allow
the sludge to burn successfully in suspension. (This was verified during test
runs 16A, 16B, and 17B, where bottom ash carbon content was less than one
percent.)
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DATA ACQUISITION SYSTEM
Plant operating data for all runs was collected manually and with an
automatic, computer-based data acquisition system. Table 4, developed by APCI,
lists the data acquired, and Figure 2, also developed by APCI, indicates the
location of instrumentation. Additionally, thermocouples were installed to
measure grate temperature, and HC1 monitoring equipment was provided during Phase
I. Bottom and fly ash was sampled during each run and analyzed for:
arsenic
barium
cadmium
chromium
lead
mercury
selenium
silver
chloride
sulfate
unburned carbon
"Toxicity characteristic leaching procedure" (TCLP) was not performed given
that, during the pilot test, fly ash was collected separately, prior to the air
pollution control system, and therefore would not have had the benefit of mixing
with lime from a dry scrubber system as is common in commercial installations.
It was therefore agreed that TCLP testing would not be performed in that it would
not be representative of the ash generated by commercial facilities. Flue gas
moisture was determined manually once per test run. All instrumentation was
calibrated prior to and after each run to ensure data accuracy.
APCI analyzed all the raw data collected to screen out non-representative
information collected during periods when the feed hopper was plugged or when
failure of the flue gas sampling probe or incomplete combustion of sludge,
determined by high ash carbon content, occurred. As a result of this data
screening, the runs in Table 5 were eliminated. The successful runs that
remained and were used in the evaluation are given below in Table 6.
TABLE 6. COMPLETED TEST RUNS
TEST DESCRIPTION
PHASE I TEST RUNS
PHASE II TEST RUNS
Baseline
MSW/02
MSW/Sludge
MSW/02/Sludge
7A, 8A, 13A, 14A
7B, 7C, 9A, 13B, 13C, 14B,
14C
16A, 16B, 17B
20, 22A, 23A, 24A
22B, 26B
22C, 23B, 23C, 24B,
24C, 25B, 25C
- 13 -
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TABLE 5. ELIMINATED TEST RUNS
RUNS PROBLEM
3A Flue gas sampling probe had been leaking
38 Flue gas sampling probe had been leaking
4A Flue gas sampling probe had been leaking
48 Flue gas sampling probe had been leaking
88 Incomplete combustion of sludge when utilizing extrusion plate
10A Incomplete combustion of sludge when utilizing extrusion plate
10B Incomplete combustion of sludge when utilizing extrusion plate
HA Incomplete combustion of sludge when utilizing extrusion plate
12A Incomplete combustion of sludge when utilizing extrusion plate
12B Incomplete combustion of sludge when utilizing extrusion plate
17A Poor energy balance closure and sludge atomization nozzle erosion
problems.
17C Poor energy balance closure and sludge atomization nozzle erosion
problems.
21 Poor energy balance closure.
- 16 -
-------
DATA PRODUCTION
Phase I
Baseline Testing--
The testing program required a baseline to be established, which required
firing MSW only and establishing the base operating conditions. The control
point for the baseline was 8.5 percent oxygen concentration in the flue gas (on
a wet basis) while maintaining a slight negative pressure in the combustion
chamber. Four baseline runs were performed (7A, 8A, ISA, and 14A).
Oxygen-Enriched MSW Incineration--
The effect of oxygen enrichment on MSW combustion with no sewage sludge was
determined during runs 7B, 7C, 9A, 13B, 13C, 14B, and 14C.
The control point was 8.5 percent oxygen concentration in the flue gas, on
a wet basis. The mass limit of the grate was also intended for use as a control
point. However, due to induced draft fan limitations, the grate mass limit could
not be reached. As a surrogate, the fire-line position, where visible combustion
actually commences, on the grate was used. The reference point fire-line
position was established during the baseline runs and was visually monitored
through an observation port located at the ash discharge end of the pilot test
unit. To provide margin, the fire-line reference point was established at a
position where the induced draft fan was operating at less than full capacity.
Oxygen-Enriched Co-Incineration of MSW and Sewage Sludge--
During the latter part of Phase I testing, APCI acquired a proprietary air-
aspirated nozzle, which was installed, functioned satisfactorily, and enabled
runs 16A, 16B, and 17B to be performed.
Phase II
Due to the problems encountered during Phase I, which limited actual test
results of MSW and sewage sludge co-incineration with oxygen to those obtained
from three runs, the Phase II test plan was modified by APCI to focus more on the
co-incineration of MSW and sewage sludge with oxygen than on determining optimal
ratios.
Baseline Testing--
Phase II testing was conducted in September 1992, seven months after the
completion of Phase I testing, and consequently required additional MSW to be
obtained. To account for any differences from the MSW used during Phase I
testing, baseline testing was again performed. Control points were 8.5 percent
oxygen concentration in the flue gas, on a wet basis, while maintaining the fire
line at a fixed point. Four baseline runs (20, 22A, 23A, and 24A) were
performed.
MSW and Sewage Sludge Co-Incineration Without Oxygen Enrichment--
To determine the effects on the pilot unit of co-incinerating MSW and
sewage sludge without oxygen enrichment, testing was performed at dry-siudge-to-
- 17 -
-------
MSW ratios of 5.1 percent and 11.3 percent, using the sludge atomization nozzle
Control points were 8.5 percent oxygen concentration in the flue gas, on a wet
basis, and maintaining the fire line at a fixed point determined during baseline
testing Two co-incineration with no oxygen-enrichment test runs (22B and 26B)
were performed. v '
Oxygen-Enriched Co-Incineration of MSW and Sewage Sludge--
The control points for the oxygen-enriched co-incineration of MSW and
sewage sludge were 8.5 percent oxygen concentration in the flue gas, on a wet
basis, and maintaining the fire line at a fixed point determined during baseline
testing. Oxygen was introduced through the sludge atomization nozzle and the
hnnrrM7? ?
-------
SECTION 4
PROGRAM RESULTS
DATA REDUCTION
Throughout both phases of the entire test program, data was collected to
enable APCI to perform heat and material balance calculations for each test
performed.
Based on the data collected, and by accounting for all the mass, the mass
and energy balance program solved for the MSW ultimate analysis (i.e., C, H, 0,
H20, and ash). From the ultimate analysis, the MSW higher heating value was
estimated, which was used in determining the total energy input to the system.
Figure 3, developed by APCI, provides a schematic representation of the heat and
material balance.
To account for air leakage, the results were adjusted by varying the tramp
air flow until the amount of total mass entering the system and the amount of
total mass leaving the system closed to within 1 percent.
Using the boiler as a calorimeter to account for total heat and accounting
for the mass flow around the combustion unit provides a better estimation of the
average MSW composition and HHV combusted during a run than a laboratory analysis
of a grab sample. This is due to the nonhomogenous nature of MSW, which does not
lend itself to accurate determination of composition over short time spans with
few samples. Sludge, on the other hand, has more uniform consistency, and
laboratory analysis provides a reasonable representation of sludge
ultimate/proximate analysis and heat content.
Phase I
Oxygen-Enriched MSW Incineration--
The effect of oxygen enrichment on MSW combustion with no sewage sludge was
determined by runs 7B, 7C, 13B, 13C, 14B, and 14C and was compared against
baseline runs 7A, 8A, 13A, and 14A.
APCI's reported results, based on actual data and not normalized to a
constant flue gas flow rate and oxygen concentration (wet) in the flue gas,
indicated that by adding 98.0 kg/hr (216 Ibs/hr) of oxygen, MSW throughput
increased to 322.5 kg/hr (711 Ibs/hr), or almost 20 percent over the 270.8 kg/hr
(597 Ibs/hr) average baseline case.
- 19 -
-------
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Normalizing both the baseline data and the results of the oxygen-enriched
co-incineration runs to 8.5 percent oxygen concentration (wet) in the flue gas
and a 2,268 kg/hr (5,000 Ib/hr) flue gas flow rate, as shown in Table 7, enabled
an approximate 24-percent increase in MSW throughput with the addition of 98
kg/hr (216 Ibs/hr) of oxygen. Figures 4A and 4B provide plots of these results
in metric and U.S. units, respectively.
Oxygen-Enriched Co-Incineration of MSW and Sewage Sludge--
The effects of oxygen enrichment on the co-incineration of MSW and sewage
sludge were determined during runs 16A, 16B, and 17B.
During the latter part of Phase I testing, APCI acquired a proprietary air-
aspirated nozzle which functioned satisfactorily. The nozzle introduced sludge
to the pilot unit in small enough particle sizes to allow the sludge to burn in
suspension.
The bottom ash carbon content for runs 16A, 16B, and 17B was analyzed, with
results of .33, .91, arid .68 on a weight-percent basis, respectively, indicating
good burnout.
Runs 16A, 16B, 17B, and the baseline runs were normalized to 8.5 percent
oxygen concentration, on a wet basis, in the flue gas and a flue gas flow rate
of 2,268 kg/hr (5,000 Ibs/hr).
The results of runs 16A, 16B, and 16C were compared against the average of
the results of the baseline runs, and, as shown in Figures 5A (metric units) and
5B (U.S. units), while maintaining a consistent MSW-feed rate, flue gas flow, and
oxygen concentration, sludge was co-incinerated with MSW with the addition of
oxygen. During these runs the atomizing nozzle was corroding. Material
modifications corrected this problem for Phase II testing.
Phase II
MSW and Sewage Sludge Co-Incineration without Oxygen Enrichment--
Three runs (16C, 22B, and 26B) were conducted with sludge co-incinerated
with MSW with no oxygen enrichment. Table 8, developed by APCI, is a comparison
of all data obtained from baseline runs, MSW and sludge co-incineration runs
without oxygen enrichment, and MSW co-incineration runs with oxygen enrichment,
normalized to an oxygen concentration of 8.5 percent (on a wet basis) in the flue
gas. The average first-pass temperature (i.e., T101 on Figure 2) decreased from
the baseline 835°C (1,535°F) to 729°C (1,345°F). As shown in Figures 6A (metric
units) and 6B (U.S. units), at the point for zero oxygen addition (which is the
average of the co-incineration runs without oxygen enrichment) there was a
decline in the MSW-feed rate with the addition of sludge. The total MSW and
sludge feed rate (fuel rate) increased, however, over the baseline.
Table 9, also developed by APCI, shows increases in the concentration of
CO and total hydrocarbon in the flue gas for runs 22B and 26B.
- 21 -
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Consequently, even though MSW and sludge were successfully co-incinerated
without oxygen enrichment, there were effects on operating conditions which
adversely affected flue gas emissions by increasing the concentrations of CO and
total hydrocarbon.
Oxygen-Enriched Co-Incineration of MSW and Sewage Sludge--
Ten runs (16A, 16B, 17A, 22C, 23B, 23C, 24B, 24C, 25B, and 25C) were
conducted with sludge co-incinerated with MSW and oxygen enrichment. Table 8
indicated that with oxygen concentration normalized to 8.5 percent (wet) in the
flue gas, average first-pass temperatures were 835°C (1,535°F) for baseline runs
and 847°C (1,556°F) for oxygen-enriched co-incineration, indicating an ability
to maintain temperature stability.
Figures 7A (metric units) and 7B (U.S. units), developed by APCI, plot
normalized first-pass temperatures against oxygen requirements in pounds per dry
pound of sludge, and estimated that to maintain an average-base first-pass
temperature of 835°C (1,535°F), as established during the baseline runs,
approximately 3.5 to 5.5 kilograms (pounds) of oxygen per kilogram (pound) of dry
sludge would be required. This is a reasonable estimate based on the limited
testing performed, however the range is very broad. Figures 6A and 6B showed the
effect of oxygen enrichment on co-incineration of MSW and sewage sludge. Sludge
was co-incinerated with MSW up to a maximum ratio of 11.3 percent dry sludge per
pound of MSW.
Phase I and Phase II
Bottom and Fly Ash--
Bottom and fly ash was sampled and analyzed throughout the pilot
demonstration program. Table 10 presents the results of these analyses.
The effects of oxygen-enriched incineration of MSW and co-incineration of
MSW and sewage sludge do not appear to have a significant effect on the heavy
metal content of the ash product. Lead content had the most variability and it
was most likely a function of the lead content of the MSW itself.
Hydrochloric Acid--
Flue gas HC1 concentrations were measured during Phase I of the pilot test
program and ranged from approximately 250 to 400 ppm when measured in the
untreated flue gas.
The results of the measurements were plotted against the first pass
temperature and are presented in Figure 8.
The data is scattered with little or no apparent correlation to first-pass
temperature. However, test runs performed on the same day have similar levels
of HC1 concentrations (i.e., 13B and 13C and 14B and 14C) suggesting that flue
gas HC1 concentrations are more a function of the chlorine content of MSW and/or
sewage sludge.
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Total Hydrocarbons--
r«,,™ AS WaiSi sl?ownu.onuTable 9> co-incineration in conjunction with 0,-.
could result in higher uncontrolled emission of hydrocarbons than ^u,^, ,v
nrS^ HWlHh HSWJ"c1nerat1on. Additionally, as* shown on Figure 8A wh h
provides a hydrocarbon emissions trend for run 26B (co-incineration without
oxygen enrichment) conducted during Phase II, hydrocarbon emissions can be
dramatically affected by upsets in incinerator operation. emissions can be
INDEPENDENT VERIFICATION OF TEST RESULTS
Theoretical Comparison of Reported Results
tho ADPT and actual flue gas C02 concentrations were
replicated The flue gas and oxygen-flow rates were' then compared for
consistency to the reported results. Tables 11A (metric units) and 11B (U S
units) compare the reported results to the theoretical results for the Phase'l
testing and Tables 12A (metric units) and 12B (U.S. units) compare the reported
results to the theoretical results for the Phase II testing. reported
cases, i.e.,
As noted, the data compared very favorably with flue-gas flow in most
i.e., within 1 to 2 percent, and in a few cases in excess of 3 percent
^tfc CaHSe+SK t,h.epj:theor:eti1ca1 ^gen flow rates were higher than the reported
rates, and the differential ranged from a low of .91 kg/hr (2 Ibs/hr) to a hiah
of 15.42 kg/hr (34 Ibs/hr), with an average of 7.26 kg/hr (16 Ibs/hr) As an
alternative comparison Run 24C, which showed the highest oxygen flow
differential [15.42 kg/hr (34 Ibs/hr)] was checked using a theoretical combustion
calculation, as previously discussed, except that oxygen concentration was varied
?n the reported oxygen flow rate was replicated. Theoretical flue gas, 0,,
C02, and H20 concentrations were compared to APCI's reported results, and in af
cases
cases the differential was less than 3 percent.
Conclusion
The reported results of each APCI test have been verified by CSI, using an
alternative theoretical approach which yielded comparative differentials of less
than 3 percent. It can therefore be concluded that APCI's reported results
performed °UtC°me °f ^ ^^ pi1ot-scale Demonstrating program
- 37 -
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TECHNICAL AND OPERATIONAL IMPLICATIONS
Existing Facilities
Application of an oxygen-enrichment system to an existing waste-to-energy
facility for the purpose of sewage sludge co-incineration with MSW would require
a major capital investment as well as facility modifications. These
modifications would include, at a minimum:
• a sludge receiving and storage area, including storage tanks or
pits, depending upon the solids content of the as-received sludge;
• sludge transfer equipment, including conveyors and/or pumps;
• sludge conditioning equipment, to provide for grinders, and water
addition if necessary;
• positive-displacement sludge pumps for delivering sludge to the
furnace;
• nozzles for delivering sludge into the furnace;
• air compressors for atomization of the sludge delivered to the
furnace;
• boiler modifications to enable nozzles to be installed into the
furnace properly; and
• siting and installation of an oxygen-production facility.
The majority of the necessary facility modifications can be made while the
facility is operational. The only interface that would affect operations is the
installation of the sludge atomization nozzles in the boiler wall, which could
potentially be accomplished during one or more scheduled outages, thereby
minimizing the impact on existing operations.
Prior to its commercial application, it is important that the oxygen-
enrichment technology be demonstrated over a prolonged period of time so as to
- 43 -
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determine whether it has any negative impacts on the boiler and facility, such
as:
• Increased fouling and erosion of superheater and boiler tubes.
• Operational problems that affect the facility's availability and
consequently, the ability to meet contract obligations.
• Corrosion problems associated with boiler duct work, air pollution
control equipment, and stacks.
• Adverse operational problems with existing air pollution control
equipment due to increased moisture content and pollutants.
• Need to add additional air pollution control equipment.
• Decrease in the facility's net power production, exclusive of the
additional power required to produce oxygen.
New Facilities
Given that most vendors already have available to them technology designed
for co-incinerating sewage sludge with MSW without detriment to MSW throughput
and could provide it at the design stage for new facility applications
incorporation of an oxygen-enrichment system into a new facility would likely be
unnecessary. These technologies, for the most part, require sludge to be dried
prior to being introduced into the furnace. Some examples are as follows.
• American Ref-Fuel's co-incineration system, which utilizes Deutsche
Babcock Analgen technology, includes a direct flash-dryer, a drying
mill, interconnecting refractory-lined duct work, and sludge
handling equipment., Flue gas is withdrawn from the first boiler
pass at temperatures in excess of 857°C (1,600°F) and directed to
the flash dryer above the drying mill. The sludge cake is
introduced into the flash-dryer using saturated steam for
atomization. From the contact chamber, the sludge is ground, dried
to 90-percent solids, and injected into the furnace.
• Katy-Seghers' co-incineration system uses an indirect drying process
whereby energy is transferred from the exhaust gases to an oil
medium. The oil medium is pumped to a multi-tray dryer where the
sludge is dried. The dried sludge is then directly mixed with
refuse in the feed hoppers.,
• Martin co-incineration technology requires minimal drying, and
sludge is delivered into the furnace utilizing a twin-screw
discharger that compresses the sludge before it is fed to a roller-
spreader that spreads the material over the refuse bed
- 44 -
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In all these cases, the water vapor is introduced into the furnace to
destroy odors. These vendors have had operational experience (foreign) with
their systems and would likely need strong technical and economic incentives to
depart from their designs and accommodate an oxygen-enrichment system.
Operational Considerations
The operational requirements of an oxygen-enrichment system on either an
existing or new facility would require:
• additional labor for sludge receiving, handling, operation, and
maintenance;
• additional equipment reserve funds for equipment replacement;
• interface with the oxygen-production facility;
• provisions for disposal of the additional ash generated by sludge
combustion;
• operational considerations relative to modifications to the existing
air pollution control equipment and;
• potential oxygen facility operational responsibilities.
ENVIRONMENTAL REGULATORY AND PERMITTING REQUIREMENTS
The U.S. EPA has promulgated rules and regulations which establish
permitting requirements and performance standards applicable to both MSW and
sewage sludge incinerators. The state agencies, for the most part, have
essentially adopted these requirements, and standards of more stringent criteria,
in their regulations. These federal and state regulations have been or will soon
be revised to comply with the provisions of the Clean Air Act Amendments of 1991.
Described below are the current and anticipated environmental regulations
that could potentially impose constraints or performance criteria on municipal
incinerators designed to co-incinerate sewage sludge with MSW.
Permitting Requirements
Before initiating construction, the owner or operator of a new municipal
incinerator must submit applications for several permits to either the EPA or
responsible state agency. For a modified facility, the owner/operator may be
required to submit an application for permit amendments to these agencies. In
either case, the permit application must demonstrate compliance with performance
standards applicable to the source category, as well as ambient air quality
criteria in the vicinity of the source. The applicable permitting requirements
are contained in the following federal and state regulations:
• Prevention of Significant Deterioration regulations;
- 45 -
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• Nonattainment Area regulations; and
• state air and solid waste regulations.
These regulations are discussed below in the context of municipal
incinerators designed to burn sewage sludge in combination with MSW.
Prevention of Significant Deterioration Regulations--
According to the Prevention of Significant Deterioration (PSD) regulations,
the owner/operator of a "major" source located in an attainment or unclassified
area must obtain a PSD permit before initiating construction. For a modified
major source, the owners/operators would be required to obtain a PSD permit if
the modification resulted in a "significant" increase in the emissions of any
pollutant regulated under the Clean Air Act. A significant emissions increase
is defined by the de minimis emission rates issued by the EPA. A major
stationary source is defined in the PSD regulations as any source included in a
list of 28 specified categories with the potential to emit 90.7 tonnes (i e
metric tons) per year (100 TPY) of any regulated pollutant. These 28 source
categories include municipal incinerators with an aggregate capacity greater than
227 tonnes per year (250 TPY).
The owner/operator of a modified major source must meet the following
requirements in accordance with the PSD regulations:
• apply Best Available Control Technology (BACT) for all regulated
pollutants emitted in significant quantities;
• assess ambient air quality in the vicinity of the source using
representative data from either a preconstruction monitoring program
or an existing monitoring station;
• demonstrate compliance with ambient air quality standards and PSD
allowable increments following operation of the modified source; and
• analyze the effects of source operation on soils, vegetation, and
visibility, and the impacts of secondary growth in the vicinity of
the source.
A source located within a nonattainment (NA) area for a given criteria
pollutant is exempt from the PSD regulations; rather, the source may be subject
to the NA Area regulations for that pollutant.
A municipal waste incinerator [greater than 227 tonnes per day (250 TPD)
total MSW throughput] invariably emits more than 90.7 tonnes per year (100 TPY)
of several regulated pollutants and thus is classified as a major source under
the PSD regulations. Accordingly, a new municipal incinerator would be required
to obtain a PSD permit prior to construction whether or not it is designed to
burn sewage sludge with MSW. A modified facility could also be required to
obtain a PSD permit if co-incineration results in a significant increase in the
emission rate of any regulated pollutants. As was shown on Table 9, co-
incineration in conjunction with 02-enrichment could result in higher
- 46 -
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uncontrolled emissions of sulfur dioxide (S02), nitrogen oxides (NO), carbon
monoxide (CO), and hydrocarbons (HC) than typically experiencedxwith MSW
incineration. Co-incineration could also result in higher uncontrolled emissions
of certain trace metals and, possibly, semi-volatile organic compounds, depending
on the combustion conditions and sewage sludge composition. The controlled
emissions from new facilities, however, should be similar to those associated
with MSW incineration, because of the mandated air pollution control systems for
new municipal waste combustors (i.e., combustion controls, selective noncatalytic
reduction, spray dryer absorbers, and baghouses). For modified facilities, co-
incineration with 02-enrichment would likely result in a significant increase in
NOX emissions, since existing facilities may not incorporate selective
noncatalytic reduction (SNCR) for NOX control. This significant increase in NO
emissions would trigger a PSD permit for the necessary modifications. x
Nonattainment Area Regulations--
The owner or operator of a major source of a given criteria pollutant,
which is located in an NA area for that pollutant, must meet the requirements of
the NA Area regulations. For a modified major source, the owners/operators are
subject to these requirements if the modification results in a "significant"
increase in the emissions of the subject pollutant (see Table 13). A major
source is defined in the NA Area regulations as one that emits more than 90.7
tonnes per year (100 TRY) of the subject pollutant. The Clean Air Act Amendments
of 1991, however, revise the definition of a major source of volatile organic
compounds (VOC) depending on the classification of the NA area -- a source
emitting 90.7 tonnes per year (100 TRY) in marginal or moderate areas, 45.4
tonnes per year (50 TRY) in serious areas, 22.7 tonnes per year (25 TRY) in
severe areas, and 9.1 tonnes per year (10 TRY) in extreme areas.
According to the NA Area regulations, the owner/operator of a modified
major source must meet the following requirements:
• comply with Lowest Achievable Emission Rate (LAER) for that source
category;
• obtain contemporaneous emission offsets for the subject criteria
pollutant;
• demonstrate a net air quality benefit for that pollutant in the
vicinity of the source; and
• ensure that all sources owned by the applicant within the state
comply with applicable regulations.
Again, a municipal waste incinerator [greater than 227 TRY tonnes per year
(250 TRY) total MSW throughput] typically emits more than 90.7 TRY tonnes per
year (100 TRY) of particulates, SO,, NOX, and CO. Accordingly, a new facility
located in an NA area for these pollutants would be required to comply with the
LAER, emissions offset, net air quality benefit, and other requirements of the
NA Area regulations. For modified facilities, the existing air pollution control
systems would likely maintain particulate, S02, and CO at their current levels,
- 47 -
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State Air and Solid Waste Regulations—
The various state agencies have also promulgated regulations establi
performance standards and permitting processes for municipal " nclnerators ce
SLTT1"6™11"9**8?*98 Sludge 1n Combination with Vw The perforance
standards represent the minimum performance criteria for the air noVlntinn
control systems applied to the facility. In addition, they must be at least «
stringent as the emission limit specified in the applicable federal standards and
^^
associated performance levels. The state regulatory agency would definitely
require an air permit for a new municipal incinerator For a mod fled Surce
r or a mo led urce
the state agency would typically review the air permit for an exist no municipal
tKp1lepr«t0r 't '• lfnecetssa^> would require a permit amendment before a" owing
the operator to incinerate sewage sludge at the modified facility. Depend MOT
the state, the permit application should also satisfy the requirements of the PSD
and NA Area regulations. The review of the permit application could be a length?
process and would typically entail providing public notice and holding public
hearings on the proposed modifications. "uiaing puonc
tn ,1J;°Vr'mUniCJPalincinerators' a Sol1d waste Permit would also be required
to allow the operator to receive and process sewage sludge at the facility A
permit amendment would almost certainly be required for modification of' an
existing incinerator The permit application typically would include process
description, sewage sludge composition, plans, and specifications operat^nq and
maintenance procedures, and other pertinent information. Similar to the air
permit, the review process would typically entail public notice and hearings
Performance Standards - -
quidellnLEP?ha,td fmnnt *gT™S have issued performance standards and emission
guidelines that impose design and operational constraints on municioal
incinerators. These include the following regulations: municipal
Guidelines! ^0™"" Standards and Section lll(d) Emission
National Emission Standards for Hazardous Air Pollutants.
annHr»MS6?ted be!°Vre the Performance standards and emission guidelines
appl cable to municipal incinerators modified to co-incinerate sewaae s lurial in
combination with MSW. Note that the recently promulgated ^standards for s^waqe
sludge incinerators (40 CFR 503, Subpart E) apply only to those "devTces in wMch
- 49 -
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only sewage sludge and auxiliary fuel are fired." These standards, therefore
are not applicable to co-incineration facilities. '
New Source Performance Standards--The New Source Performance Standards
(NSPS) constitute a set of national emissions standards that apply to specific
categories of new sources. Pursuant to Section lll(d) of the Clean Air Act, the
EPA may also establish emission guidelines intended to assist state agencies in
the development of standards for existing facilities. To date, the EPA has
promulgated NSPS and/or emission guidelines applicable to municipal waste
combustors and industrial boilers -- both would impose emission limits and
operating requirements on co-incineration facilities.
Municipal Waste Combustors. On February 11, 1991, the EPA promulgated the
NSPS for new municipal solid waste combustors (MSWCs) having a unit
capacity greater than 227 TPD tonnes per day (250 TPD) (40 CFR 60, Subpart
Ea). Coincidentally, the EPA promulgated Section lll(d) emission
guidelines for existing MWCs (40 CFR 60, Subpart Ca). These standards and
guidelines establish emission limits for MWC metals (measured as
particulate matter), MWC organics (dioxins and furans), MWC acid gases (SO,
and HC1), and nitrogen oxides (NO ). They also specify minimum criteria
for "good operating practices/ operator certification, performance
testing, continuous monitoring, and reporting and recordkeeping.
According to Section 129 of the 1990 Clean Air Act Amendments, the EPA is
required to revise the NSPS and emission guidelines for MWCs with a
capacity greater than 227 TPD tonnes per day (250 TPD) within 12 months of
enactment of the amendments. However, the EPA has recently indicated that
the revisions will not be proposed until June 1993. The amendments
require that, at a minimum, numerical limitations be specified for
particulate matter, opacity, S02, HCL, NOX, CO, dioxins/furans (PCDD/PCDF),
lead (Pb), cadmium (Cd), and mercury (Hg). Table 13 (presented
previously) and Table 14 summarize the emission limitations specified in
the existing and expected NSPS and emission guidelines, respectively.
As previously indicated, co-incineration with 02-enrichment could result
in higher uncontrolled emissions of S02, NOX, and CO than found in MSW
incineration. Depending on the combustion conditions and sewage sludge
composition, co-incineration could also result in higher uncontrolled
emissions of Pb, Cd, Hg, and possibly, PCDD/PCDF. Despite these
potentially higher uncontrolled emission levels, the air pollution control
systems required by the NSPS should ensure compliance of new facilities
with the emissions limits for S02, NOX, CO, Pb, Cd, Hg, and PCDD/PCDF. It
should be noted that an increase in uncontrolled NOX emissions could push
the performance envelope of commercially available SNCR processes. For
modified facilities, co-incineration with 02-enrichment would likely result
in an increase in uncontrolled NOX emissions, which could necessitate the
retrofit of SNCR to ensure compliance with permit conditions (the
guidelines do not specify an NOX emission limit). Likewise, an increase
in CO emissions could require modification of the combustion control
- 50 -
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TABLE 14. EXISTING AND EXPECTED NEW SOURCE PEFORMANCE STANDARDS
APPLICABLE TO NEW MUNICIPAL WASTE COMBUSTORS
[greater than 227 TPD metric (250 TPD)]
POLLUTANT
Particulate Matter
Visible Emissions
S02
HC1
NOX
CO
PCDD/PCDF
Pb
Cd
Hg
UNITS
gr/dscm @ 7% 02
(gr/dscf @ 7% 02)
% opacity
% reduction
ppmdv @ 7% 02
% reduction
ppmdv @ 7% 02
ppmdv @ 7% 02
ppmdv @ 7% 02
ng/dscm @ 7%02
ng/dscm @ 7%02
ng/dscm 0 7%02
% reduction
ug/dscm 0 7% 02
PERFORMANCE
Existing
0.530
(0.015)
10
80
30
95
25
-
50-150
30
-
-
-
STANDARDS
Expected
0.530
(0.015)
10
80
30
95
25
180
50-150
30
160
20
80
100
Existing standards issued on February 11, 1991; possible revisions to the
expected standards developed in July 1992.
- 51 -
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system or installation of auxiliary burners to meet either the emission
guidelines or permit conditions.
Industrial Boilers. The EPA promulgated the NSPS for Industrial-
Commercial -Institutional Steam Generating Units (40 CFR 60, Subpart Db) on
July 13, 1985. These standards apply to industrial boilers with heat
inputs greater than 25.2 x 106 kilocalories/hr (100 MMBtu/hr). They limit
the emission of particulate matter, S02, and NO, from various types of
industrial boilers burning both fossil and non-dossil fuels (including
municipal solid waste). Because these NSPS are less stringent than those
^El1*? S,,r° 5SJ a,new or modified facility would be required to comply
with the MWC standards, rather than the industrial boiler standards in
accordance with EPA policy.
. National Emission Standards for Hazardous Air Pollntant<:-ThQ National
Emission Standards for Hazardous Air Pollutants (NESHAP) are a set of emission
standards that apply to both new and existing sources of hazardous air pollutants
listed by the EPA. To date, the NESHAPs for beryllium and mercury are the only
with MSWS ^ ^ t0 6Xisting MWCs burnin9 Sewa9e sludge in combination
Beryllium. The NESHAP for beryllium (40 CFR 51, Subpart C) limit
emissions from incinerators processing "beryllium-containing waste" to 10
grams over a 24-hour period. Alternatively, the EPA Administrator may
allow the facility operator to meet an ambient beryllium concentration of
0.01 ug/m average over a 30-day period. Beryllium-containing waste is
defined in the standards as a material contaminated with beryllium and/or
beryllium compounds used or generated during any process or operation
performed by a source subject to this subpart (Subpart C). Because such
waste is almost never processed in municipal incinerators, the NESHAP for
beryllium generally are not applicable to these sources whether burning
MSW alone or in combination with sewage sludge.
Mercury. The NESHAP for mercury (40 CFR 61, Subpart E) limit emissions
from sewage sludge incineration and/or drying plants to 3,200 grams over
any 24-hour period. The NESHAP also impose stack sampling and sludge
analysis requirements on affected facilities. These standards would apply
^rJcNlpan incjnerators modified to burn sewage sludge in combination
with MSW Depending on the capacity of the MWC and the composition of the
sewage sludge, mercury control (e.g., activated carbon injection) could be
NESHAP °n co"incineration facilities to ensure compliance with this
ECONOMIC IMPLICATIONS
CSI has estimated the potential costs of retrofitting an existing 680-
tonne-per-day (750-TPD) waste-to-energy facility to co-incinerate municipal
sewage sludge utilizing oxygen enrichment, based on preliminary budgetary capital
and operating cost estimates developed by CSI. The costs of implementing a new
oxygen-enriched co-incineration facility were not estimated, since, as discussed
- 52 -
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previously in this section, incorporating the APCI system would likely not
enhance the technologies of, nor likely present an economic advantage to vendors
of, state-of-the-art co-incineration facilities.
Four cases were evaluated (Table 15):
TABLE 15. CASES EVALUATED
CASES
Case 1
Case 2
Case 3
Case 4
MSW
tonnes
(tons)
680 (750)
680 (750)
680 (750)
680 (750)
WET SLUDGE
tonnes
(TPD) @ 15%
solids)
181 (200)
544 (600)
181 (200)
544 (600)
OXYGEN/DRY SOLIDS
Kg/Kg
(Ib/lb)
1.59 (3.5)
1.59 (3.5)
2.49 (5.5)
2.49 (5.5)
OXYGEN
tonnes per day
(TPD)
95 (105)
286 (315)
150 (165)
449 (495)
Capital Costs
Estimated capital costs for making waste-to-energy facility modifications
so as to co-incinerate sludge with oxygen enrichment were based on recent
quotations for new sludge co-incineration facilities and are as shown on Table
16.
TABLE 16. ESTIMATED FACILITY-RETROFIT CAPITAL COSTS:
181/544 METRIC TPD (200/600 TPD) OF WET SLUDGE
(15% solids)
($1993)
COST ELEMENT
Subtotal
Contingency @ 10%
TOTAL CAPITAL COSTS
181 METRIC TPD
(200 TPD)
($000)
6,800
680
544 METRIC TPD
(600 TPD)
($000)
Architectural & Engineering
Management Support & Activities
Site Work
Buildings
Equipment
Instrument & Control/Electrical
Boiler Modifications
$ 410
200
270
530
4,500
390
500
$ 880
440
580
1,140
9,700
830
1,000
14,570
1,460
- 53 -
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Estimated capital costs for the oxygen-production facility necessary to
supply the oxygen required are based on estimated costs from suppliers who
furnish this type of facility and do not include any land acquisition costs The
costs are shown in Table 17.
TABLE 17. ESTIMATED OXYGEN-PRODUCTION FACILITY CAPITAL CO
CTC
FACILITY
FACILITY COST
($000)
95 metric-TPD (105-TPD) Oxygen Production
150 metric-TPD (165-TPD) Oxygen Production
286 metric-TPD (315-TPD) Oxygen Production
449 metric-TPD (495-TPD) Oxygen Production
Facility
Facility
Facility
Facility
4,690
6,553
10,368
14,486
Low-pressure oxygen at an oxygen purity of approximately 90%.
Operating and Maintenance Costs
Estimated additional costs to operate and maintain a waste-to-energy
facility retrofitted to co-incinerate either 181 or 544 tonnes per day (TPD) of
sludge are shown in Table 18.
The estimated additional operating and maintenance cost of an oxygen-
production facility are shown in Table 19. These costs are based on estimated
costs from suppliers of this type of facility and assume:
• 1,440 x 106 joules (400 kWh) consumed per ton of oxygen produced;
• an operating and maintenance labor force of six for a 272-tonne-per-
day (300-TPD) oxygen facility (assume $40,000/year salary); and
• an allowance of approximately 1.75 percent of capital for equipment
reserves.
Summary of Economic Analysis
As shown in Table 20, the first-year cost on a per-dry-tonne (per-dry-ton)
basis varies from $353 to $452 per dry tonne ($320 to $410 per dry ton) for a
181-tonne (200-TPD) (wet) facility, and from $287 to $364 per dry tonne ($260 to
$330 per dry ton) for a 544-tonne (600-TPD) (wet) facility, depending upon the
amount of oxygen consumed. As discussed previously in this report, during the
test runs, the amount of oxygen consumed varied from 3.5 to 55 kilograms
(pounds) of oxygen per kilogram (pound) of sludge (at 15-percent solids) An
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TABLE 18. RETROFITTED FACILITY ESTIMATED ADDITIONAL OPERATING AND
MAINTENANCE COSTS: 181/544 METRIC TPD (200/600 TPD) OF WET SLUDGE
(15% solids)
($1993)
COST ELEMENT
Labor*
Additional Maintenance and Service'
Equipment Reserve
Subtotal
Ash Disposal*
Subtotal O&M
Contingency @ 10%
TOTAL O&M
181 METRIC TPD
(200 TPD)
$ 40,000
170,000
131,000
341,000
130,000
471,000
47,000
$518,000
544 METRIC TPD
(600 TPD)
$ 80,000
170,000
281,000
531,000
390,000
921,000
92,000
$1,013,000
Assumes one person for 181 metric TPD (200 TPD), two persons for 544
metric TPD (600 TPD).
The additional maintenance and service is 10 percent of the base facility
maintenance and service cost in order to cover any additional costs
associated with operating the facility, including sludge-handling
equipment.
Assumes $36.28/tonne ($40/ton), 28% ash, 20% moisture content.
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TABLE 19. ESTIMATED ADDITIONAL OXYGEN-PRODUCTION FACILITY
OPERATING AND MAINTENANCE COSTS
($1993)
COST ELEMENT
FACILITY SIZE [METRIC TPO (TPH)]
95 (105) 150 (165) 286 (315) 449 (495)
O&M
Equipment Reserve
Power
Subtotal O&M
Contingency
G> 10%
TOTAL O&M
$ 80,000 $ 120,000 $ 240,000 $ 400,000
80,000 110,000 180,000 250,000
650,000 1,020.000 1,950.000 3,320.000
$810,000 $1,250,000 $2,370,000 $3,970,000
81,000
125,000
237,000
397,000
E891.000 $1,375,000 $2,607.000 $4,367.000
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TABLE 20. SLUDGE TREATMENT AND DISPOSAL COSTS
[$/dry/tonne ($/dry ton)]
CASE
1
2
3
4
SLUDGE
PROCESSED
G> 15% SOLIDS
tonnes per
day
(TPD)
181 (200)
544 (600)
181 (200)
544 (600)
02 CONSUMPTION
kg 02/kg dry
sludge
(Ib 02/lb dry
sludge)
3.5
3.5
5.5
5.5
OXYGEN
tonnes
per
day
(TPD)
95 (105)
286 (315)
150 (165)
449 (495)
SLUDGE TREATMENT
AND DISPOSAL COST
$/dry tonne
($/dry ton)
$353 ($320)
$287 ($260)
$452 ($410)
$364 ($330)
Based on construction period of one year and takes into consideration
operational impacts on the waste-to-energy facility; the addition of
Thermal DeNOx for the reduction of NOx emissions will add costs of between
$2 and $5 per ton of total waste processed by the facility, which includes
750 TPD of municipal solid waste in addition to the sludge.
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analysis of alternative methods of sludge treatment and disposal in the
northeastern U.S. indicated that costs for sludge treatment and disposal range
from $331 to $441 per dry-tonne ($300 to $441 per dry-ton). Thus, based on the
conservative budgetary capital and operating costs estimated above, the proposed
co-incineration of sludge in existing waste-to-energy facilities warrants further
examination, as the costs appear competitive on a per-dry-ton basis with
alternative sludge treatment and disposal approaches.
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SECTION 6
SUMMARY OF EVALUATION
CONCLUSIONS AND RECOMMENDATIONS
A number of conclusions can be drawn as a result of the MITE evaluation of
the Pilot Test Program. All tests performed in the Pilot Test Program were
performed in accordance with the agreed-upon protocol, except as noted in Section
3, page 10.
• The limited Pilot Test Program indicates that sludge was co-
incinerated with solid waste up to a maximum ratio of 11.3 percent
dry sludge per pound of MSW with the injection of 3.5 to 5.5
kilograms (pounds) of oxygen per kilogram (pound) of sludge, while
maintaining relatively constant MSW-feed rates.
• Based on conservative budgetary capital and operating cost
estimates, oxygen-enriched co-incineration of municipal sewage
sludge in existing waste-to-energy facilities appears competitive,
on a per-dry-ton basis, with alternative sludge treatment and
disposal approaches and therefore warrants further examination.
• Modifying an existing waste-to-energy facility to incorporate
oxygen-enriched co-incineration would likely require a permit
amendment, including an attendent review and approval process. As
such, specific permit amendment requirements, costs, and length of
the approval process should be ascertained prior to implementation.
Technical issues requiring further evaluation prior to commercial
application of APCI's oxygen-enriched co-incineration technology include:
• confirmation of the long-term reliability of the proprietary sludge
system;
• determination of the long-term impacts of the introduction of
sludge, oxygen, and moisture into existing waste-to-energy units
relative to fouling, corrosion, performance, availability, and air
pollution control equipment, including the potential need to add
additional control technology or modify existing controls; and
• determination of the effect that introduction of high moisture
sludge and oxygen into the combustion environment will have on
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organic pollution emissions, and confirmation of expected oxygen
consumption per dry ton of sludge to a range consistent with the
need to properly size and economically evaluate the oxygen
production requirements.
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