W113C
Prepublication issue for EPA libraries ENVIRONMENTAL
and State Solid Waste Manaqement Aqencies PROTECTION
AGENCY
SW1 1 3C DALLAS, T©
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This report has been reviewed by the U.S. Environmental Protection
Agency and approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the U.S. Environmental
Protection Agency, nor does mention of commercial products constitute
endorsement by the U.S. Government.
An environmental protection publication (SW-113c) in the solid waste
management series.
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ACKNOWLEDGEMENT
A great many people contributed to the effort involved in producing this
report. To our knowledge, this is the first detailed study on the use of small
modular incinerator plants, owned and operated by municipalities. The help
furnished the contractor, by so many people outside his organization,
considerably expedited the completion of the effort and solved many of the
problems that arose as the study progressed.
We would like to express our appreciation to the elected and appointed
officials of the municipalities in which each of the incineration plants were
located. They gave freely of their time and facilities; they supplied the
study and monitoring teams with much needed equipment and other resources;
they kindly accepted the inconveniences of large monitoring teams at their
plants; and provided complete access to all their records concerned with the
purchase and operation of the equipment and plants and their overall solid
waste management system.
The personnel of the Office of Solid Waste Management, U. S.
Environmental Protection Agency were invaluable in the assistance they
rendered to the study. From their experience with municipal solid waste
management, and with incinerator monitoring, they continually contributed
to the solving of various problems that arose and to decisions that had to be
reached for determining optimum monitoring methods that could be used. We are
particularly grateful to Steven J. Hitte and Allen Geswein for the help they
rendered at each test site and in the numerous conferences that led to the"
final format of this report.
Finally, we wish to express our appreciation to the management and
engineering personnel of Consumat Systems and two of their distributors,
Florida Gas Company and U. S. Recycle Corporation, who designed and constructed
the plants that were studied.
To all these groups we state that, if this study proves to be of benefit
to the municipalities who are anxious to obtain details on the advantages and
problems in incinerating municipal wastes and of waste heat recovery systems
for steam production, much of the credit for presenting the facts contained in
this report belongs to our many associates in the endeavor.
Ross Hofmann, Associates
Coral Gables, Florida
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SUMMARY OF FINDINGS
1. The incinerators studied in this report have individual waste burning
capacities of less than 50 tons per day and hence are rated as "small"
incinerators. They are installed in municipal incinerator plants in identical
modules of two to eight units to achieve the desired plant capacity. Normal
variations in municipal waste can be processed in the incinerators without
special treatment (such as shredding) before charging.
2. They utilize a controlled air principle. Municipal waste is burned
"as received" in a primary combustion chamber in a reducing atmosphere, of
insufficient oxygen for complete combustion, to minimize particulates in the
gas stream. The effluent gas is then burned in a secondary chamber, utilizing
an oxidizing or excess air atmosphere to burn the entrained particulates.
Auxiliary fuel (gas or oil) is used to assist the combustion process.
3. The incinerators operate on a batch feed basis, rather than
continuously, within a 24 hour cycle; normally being charged for seven to
eight hours; then burning down with the use of auxiliary fuel for approximately
three more hours; allowed to cool overnight; with the ash residue removed by
an operator each morning, before the start of the next 24 hour cycle.
4. Due to combustion design, and without mechanical or water-operated
pollution control devices, the gases expelled by the incinerators into the
atmosphere have very low particulate readings. Stack emissions from the tested
incinerators ranged from 0.03 to 0.08 grains of particulate matter per standard
cubic foot of dry flue gas corrected to 12 percent CC^-
5. The efficiency of thermal processing was excellent and compared
favorably with the largest municipal incinerators. Weight reduction of the
raw waste averaged 68% and volume reduction averaged 93%. Laboratory testing
of the incoming waste and the residue revealed excellent burning rates.
*6. One plant used #2 oil as auxiliary fuel; the others used natural gas.
o
Natural gas consumption per ton of waste burned averaged from 440 ft. to
1239 ft. . Oil consumption per ton of waste burned averaged 18 gallons.
7. The models tested were of different capacities. The largest burned
waste consistently at a rate of 12.5 tons per 24 hour cycle which was equal to
its design capacity. A second unit averaged during the testing period a
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burning rate of 7 tons per 24 hours, and during the test days was used from
51 to 80% of design capacity. The third unit averaged 5.8 tons per 24 hours,
and during test days was used from 58 to 89% of design capacity.
8. The characteristics of the municipal waste at the studied plants were
analyzed. Densities varied from plant to plant and sample to sample. Plant
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averages varied from 7.9 to 10.9 to 11.5 Ibs./ft during testing. Individual
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large samples (up to 1400 pounds in weight) varied from 4.6 to 24.4 Ibs./ft .
Separation studies showed wide variations in the combustible and non-
combustible fractions of the "as received" waste streams. Laboratory analyses
showed variations in moisture from 20.8% to 49.9%, and variations in heat
content on an "as received" basis from 2408 Btu/lb. to 4353 Btu/lb; and ranges
from 6596 Btu/lb to 8720 Btu/lb in the dried combustible component.
9. A waste heat recovery system produced steam from the effluent
incinerator gases as they passed through a companion boiler. During testing
47,425 pounds of steam at 100 psig were produced from burning 8.3 tons of waste
with an average value of 4353 Btu/lb. This gave a boiler efficiency of 72.8%.
10. Capital costs per ton of design capacity for all buildings, site
improvements and incinerators, completely installed, were from $9,093 to
$9,494 for straight incinerator plants. With energy recovery (steam
production), these rose to $17,667 per ton of design capacity. With interest
applied, capital costs account for from $3.57 to $4.46 per ton of waste
processed in the straight incinerator plants, and up to $7.31 per ton
processed in the steam production plant.
11. Operating costs of the incinerators on a "per ton processed" basis
varied considerably. With the straight incineration plants, the range was
from $6.26 to $15.69. The gross cost in the steam production plant was $8.75;
however, minimum steam sales revenue reduced this to a net of $2.68 per ton
processed. Labor in two of the plants was the largest operating cost element,
ranging from $3.98 to $5.74 per ton processed. Auxiliary fuel was the largest
cost in the plant using #2 oil and ran $8.17 per ton of waste processed.
Where gas was used, the fuel cost per ton of waste processed was from $0.82 to
$1.24. Water was a major cost when steam was produced.
12. Total annual costs, combining operating and capital-ownership cost
elements, compared favorably with large scale plants, ranging from $8.50 to
$18.53 per ton processed (without interest on investment) for straight
incineration, to a net of $9.99 per ton (including interest on investment) for
the steam production plant after deducting steam sales revenue.
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TABLE OF CONTENTS
PAGE
ACKNOWLEDGEMENT ............................
SUMMARY OF FINDINGS .......................... iv
1. INTRODUCTION .......................... 1
Objectives and Scope of the Study ............. 1
The Monitoring Methodology ................ 2
2. THE PROCESSING OF MUNICIPAL SOLID WASTE BY INCINERATION .... 5
3. REFUSE GENERATION ....................... 10
General .......................... 10
Pahokee Florida ...................... 11
Demography ...................... 11
Geographic Conditions ................ 12
Operation of the Municipal Sanitation Department. . . 12
Orlando, Florida ..................... 14
Demography ...................... 14
Geographic Conditions ................ 14
Operation of the Municipal Sanitation Department. . . 15
Siloam Springs, Arkansas ................. 17
Demography ...................... 17
Geographic Conditions ................ 17
Operation of the Municipal Sanitation Department. . . 18
4. TECHNICAL DESCRIPTION OF EQUIPMENT AND PLANTS ......... 21
Theoretical Considerations ................ 21
Design Considerations for the Incinerators ........ 23
Design of Steam Production Systems ............ 31
Design of Plant and Buildings ............... 36
5. PLANT OPERATION SYSTEMS .................... 47
6. THE TESTING PROTOCOL ...................... 52
Preliminary Test Arrangements ............... 53
Charging and Operation .............. .... 55
Determination of Charging Rate .............. 55
Operational Data ........ . ............ 56
Instrumentation Monitoring ................ 56
Physical Composition Determination ............ 56
Particulate Emission Testing ............... 57
Daily Monitoring Schedule ................. 58
7. WASTE LOADS AND CHARGING RATES ................. 60
Waste Deliveries ..................... 60
Charging and Burning Rates ................ 61
8. INCOMING SOLID WASTE CHARACTERIZATION ............. 64
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PAGE
Bulk Density Determination 64
Physical Composition Determination 67
By-Pass Wastes 69
9. RESIDUE CHARACTERIZATION 71
10. STACK EMISSION TESTING 74
The Test Plan 74
Stack Emission Test Protocol 74
Sampling Traverse Points 77
Gas Sample Collection 78
Visible Emissions 81
Interpretation of Stack Testing Results 81
Auxiliary Fuel 82
Emission Test Results, Pahokee, Florida 82
Emission Test Results, Orlando, Florida 86
Emission Test Results, Siloam Springs, Arkansas 90
11. LABORATORY ANALYSES OF RAW WASTES AND RESIDUES 94
Preparation of Laboratory Samples 94
Proximate Analysis 96
Ultimate Analysis 96
12. INCINERATOR EFFICIENCY 99
13. ECONOMIC ANALYSIS 103
Capital Costs 103
Vehicle Costs 106
Operating Costs 107
Comparative Total Costs 110
14. STEAM PRODUCTION FROM SMALL INCINERATORS 113
The Impact On The U. S. Energy Needs 115
15. SILOAM SPRINGS STEAM PRODUCTION 117
FOOTNOTE REFERENCES 122
APPENDICES
A. FIELD TEST REPORTS 123
B. LOWER HEATING VALUES OF TYPICAL WASTES 132
C. STACK EMISSION TESTING DATA 133
D. LABORATORY ANALYSES FORMULAS FOR ALL SITES _. 136
E. SILOAM SPRINGS STEAM SALES AGREEMENT 138
F. ENERGY CONVERSION FORMULAS 145
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PAGE
LIST OF MAPS
1. Pahokee Area 13
2. Orlando Area 16
3. Siloam Springs Area 20
LIST OF FIGURES
1. Schematic of Design Temperature Operating Range 22
2. Schematic of Design Parameter Relationships 23
3. Municipal Incinerator Module, Pahokee, Florida 26
4. Municipal Incinerator Module, Orlando, Florida 27
5. Municipal Incinerator Module, Siloam Springs, Arkansas 28
6. Automatic Loading System, Pahokee, and Siloam Springs 29
7. Automatic Loading System, Orlando, Florida 30
8. Gas Flow in Steam Production System, Siloam Springs, Arkansas. . . 34
9. Control System for Gas Flow, Siloam Springs, Arkansas 35
10. Municipal Incinerator Plant, Pahokee, Florida 38
11. Municipal Incinerator Plant with Steam Boiler, Siloam Springs. . . 41
12. McLeod Rd. Municipal Incinerator Plant, Orlando, Florida 44
13. Flow Diagram for Pahokee Municipal Incinerator 49
14. Flow Diagram for Orlando Municipal Incinerator 50
15. Flow Diagram for Siloam Springs Municipal Incinerator 51
16. Schematic Drawing of Sample Train 76
17. Sampling Points for Stack Traverses 77
18. Dry Gas Composition Sample Equipment 78
19. Steam Production Based on Waste Heat Output and Charging Rates . . 121
LIST OF TABLES
1. Incinerator Plant Monitoring Parameters 59
2. Daily Waste Loads Charged in Test Incinerators 60
3. Daily Charging and Burning Rates 62
4. Bulk Density of Raw Waste Samples 67
5. Average Physical Composition of Incoming Raw Waste 69
6. Residue Analysis 72
7. Summary of Particulate Test Results, Pahokee, Florida 83
8. Summary of Particulate Emission Test Results, Pahokee, Florida . . 84
9. Exhaust Gas Conditions in Stack, Pahokee, Florida 85
10. Summary of Exhaust Gas Analysis, Pahokee, Florida. . . 85
11. Summary of Particulate Test Results, Orlando, Florida 87
12. Summary of Particulate Emission Test Results, Orlando, Florida . . 88
13. Exhaust Gas Conditions in Stack, Orlando, Florida 89
14. Summary of Exhaust Gas Analysis, Orlando, Florida 89
15. Summary of Particulate Test Results, Siloam Springs, Arkansas. . . 91
16. Summary of Particulate Emission Test Results, Siloam Springs ... 92
17. Exhaust Gas Conditions in Stack, Siloam Springs, Arkansas 93
18. Summary of Exhaust Gas Analysis, Siloam Springs, Arkansas 93
19. Summary of Waste Analyses 97
20. Summary of Residue Analyses 98
21. Waste Reduction - Pahokee, Florida 100
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PAGE
22. Waste Reduction - Orlando, Florida 101
23. Waste Reduction - Siloam Springs, Arkansas 102
24. Breakdown of 1974 Capital Investments 105
25. 1974 Plant Vehicle Purchase Costs 106
26. Annual 1975 Operating Costs. 109
27. Comparative Annual Operating Costs FY 1974-1975 112
28. Steam Production and Fuel Consumption, Siloam Springs, Arkansas . 118
29. Total Steam Production Fuel Savings Analysis 118
30. Boiler Efficiency Analysis - Siloam Springs, Arkansas 120
LIST OF PHOTOGRAPHS
1. The Municipal Incinerator Plant, Pahokee, Florida 39
2. The Municipal Incinerator Plant, Pahokee, Florida 40
3. The Municipal Incinerator Plant, Siloam Springs, Arkansas .... 42
4. The Municipal Incinerator Plant, Siloam Springs, Arkansas .... 43
5. The Municipal Incinerator Plant, Orlando, Florida 45
6. The Municipal Incinerator Plant, Orlando, Florida 46
7. Weighing Deliveries of Waste to the Plants 63
8. Bulk Density Determination 66
9. Separation of Incoming Waste 70
10. Typical Residue from the Test Incinerators , . . . . 73
11. Stack Emission Testing Instruments 79
12. Dual Stack Emission Testing Instrumentation ..... 80
IX
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CHAPTER 1
INTRODUCTION
Objectives and Scope of the Study
In March 1975, under EPA Contract 68-01-3171, Ross Hofmann Associates
commenced a nine month investigation into the environmental aspects, operating
parameters, and economics of the use of "small" incinerators that have been
installed on a "modular" basis by various towns and cities across the United
States for the processing of municipally generated residential and commercial
solid wastes. By definition, a "small" incinerator in this investigation is
an individual furnace that burns less than 50 tons of waste during a day's
operation; and "modular" infers that one or more such incinerators, each the
same model and capacity, are installed in a municipal plant to achieve the
desired total burning capacity.
A survey of 14 manufacturers of small incinerators disclosed that there
are currently in operation 37 municipal plants that utilize the "small"
incinerator, modular approach. Each plant uses, either singly or in multiples,
incinerators with designed burning capacity of under 3,000 pounds per hour per
machine (approximately 15 tons per ten hour day). In total 95 individual
incinerators have been installed in these plants. The capacity of the machines
purchased ranges from 1,000 pounds to 2,600 pounds per hour. The design
capacities of the plants range from 5 tons to 105 tons per day. They have
been purchased by municipalities ranging from 700 to 130,000 in population.
A basic parameter of the study was that any plant to be tested had to have
been in sustained operation during the prior six months. All known
manufacturers of small incinerators were invited to participate in the study.
Many could not meet the criteria established for the testing program; others
who had municipal incinerators installed did not choose to participate in the
study.
Three towns were selected that were considered fairly representative of
the small incinerator modular approach. In each case, the municipality and the
equipment manufacturer agreed to participate in the testing and to permit
publishing of all test results.
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At each of these sites the study team conducted an investigation of the
the background on the plant, the demography of the area, the local
environmental problems, the economic advantages and constraints in such
incinerators, and the local energy parameters. This was followed by an
intensive week-long monitoring program, under normal operating conditions
while burning typical municipal waste, of a test incinerator chosen at
random at each plant.
At each site the design of the equipment, the buildings and the
operational systems were analyzed for their affect on the efficiency of
plant operations. Aspects of performance of the incinerator that were
monitored included data onrwaste input characterization; stack emissions;
use of, as well as production of energy; detailed operating parameters; and
operating costs.
The overall objective of this investigation has been to produce a
report, based on the data gathered and the observations made by the study
team, which will serve as a guide for municipalities considering such an
approach to their solid waste management; and that can also be used for
comparison purposes in future solid waste system evaluations. As this study
was being concluded, additional manufacturers of modular small incinerators
have evidenced interest in the growth of such solid waste processing in the
municipal market.
The Monitoring Methodology
The municipal incineration plants that were investigated were located
in Pahokee and Orlando, Florida,and in Siloam Springs, Arkansas. The
monitoring of each plant site lasted for five consecutive days in an effort
to ensure that the wastes being processed were typical of the community and
that the incinerators were operating normally. The Florida plants were
tested in May 1975 and the Arkansas plant in October.
For the study protocol, the methods described in the Testing Manual For
Solid Waste Incinerators (published in 1973 by the U. S. Environmental
Protection Agency) were followed.
The basic approach consists of setting aside, on the plant floor, a
quantity of waste of known weight, sufficient to sustain the incinerator
being monitored during each full day test period. This waste is then
charged into the incinerator, using regular plant operators and equipment,
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as well as charging methods; noting the time each charge is put into the
incinerator; and, noting the total burning time used by the plant for the
entire load processed that day.
While the test incinerator is being charged, the input waste is measured,
weighed, analyzed as to physical composition, and laboratory samples are
extracted for detailed analysis, daily.
While the incinerator is in normal operation, stack sampling is performed
to determine air emissions. The plant instruments are monitored to record
temperatures, and fuel, electrical and water consumption, as well as any
operational adjustments that occur.
At the completion of each day's test, the complete residue from that day
is weighed and measured to determine the efficiency of reduction, and
laboratory samples are collected for analysis.
If resource recovery is included in the operating parameters, such as
steam production and sale from burning the waste, the efficiency of the
process and its economic impact is recorded.
A daily monitoring schedule, shown in Chapter 6, was developed to perform
these evaluations at each site.
All the data for the study was gathered and the performance of the tests
was done by a joint team made up of personnel from: Ross Hofmann, Associates
of Coral Gables, Florida, acting as overall consultants on the project; Test
Services Division of Associated Service Products, Inc., Sandston, Virginia,
who handled the stack testing and monitoring of the air emissions;
the Office of Solid Waste Management Programs of the U. S. Environmental
Protection Agency, Washington, D. C., who approved all the testing protocolj
as well as contributed considerable assistance from their experience with
municipal solid waste management.
At each site the plant management was able to operate the plant in its
normal manner, despite the presence of a rather large team of outsiders and
their necessary test equipment.
The forms that were used to collect the raw data are included in
Appendix A. Within the subsequent chapters, there is a detailed account of
how the individual sites were chosen and their demography; a description of
their facilities, equipment and systems; an analysis of the operating
procedures; the methodology of data collection; economic analyses and
comparisons between the plants; and the efficiency of steam production at
the Siloam Springs plant.
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All of the plants studied had been in operation for a long enough time
before the on-site testing to have had the opportunity to have developed some
operating history. None may be termed experimental or temporary in nature,
and all are representative of like plants in other communities. All have
remained in normal operation and continue to incinerate waste on a daily
basis since the testing period.
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CHAPTER 2
THE PROCESSING OF MUNICIPAL SOLID WASTE BY INCINERATION
Many methods and systems have been designed for the processing and
disposal of municipal solid wastes. They have been influenced by many factors,
from environmental impact to economics. While landfilling and incineration
have been the most commonly used methods, both have created certain
environmental problems. Of the two methods, incineration has been the more
severely criticized in recent years, due to its potential affect on air, land
and water pollution, coupled with its cost implications. As a consequence,
landfilling has been used in the solid waste management systems of urban areas
to a far greater extent than has incineration.
From a cost viewpoint, landfilling has been cheaper than the most
efficient incineration systems. However, in many urban areas acceptable
landfill sites have become difficult to obtain and the expense of this method
has been rising steadily, with long distance hauling from collection points
and through transfer stations to a suitable site.
Solid waste management must always be viewed as a total system. All
facets of collection, transportation, processing and disposal must be
considered in any economic and environmental analysis.
Despite cost and environmental problems many municipalities have used
incinerators to process their solid wastes. In the past, municipal scale
incinerators have been defined as those having a furnace capacity of 50 tons
per day or more. In May 1972, the EPA Office of Solid Waste Management listed
193 such units in operation. This inventory was updated early in 1975 by the
American Society of Mechanical Engineers (ASME), incorporating pyrolysis units
2
and incinerators under construction and gave an operating total of only 160
units. The inventory lists the known municipal incinerators by states giving
the site location and describing the plant design. The majority of the plants
are of large capacity. Only 41 handle less than 200 tons of waste per day;
70 handle in excess of 400 tons; the average daily capacity is 415 tons. These
large municipal incinerators are concentrated in relatively few areas of the
United States. New England, New York and New Jersey house over half of the
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total inventory for the country. The age of the units, which indicates the
trend away from large-scale incineration, ranges from the early 1970's to as
far back as the late 1920's -137 were built before 1965 and 67 since then -
including operating and shut-down plants.
Evaluations have been published by EPA and other government agencies on
the efficiency, operating costs and environmental effects of some of these
municipal units. The principal study of such plants was presented to the 1970
National Incinerator Conference and covered seven municipal incinerators with
analyses on the quality and quantity of solid waste they processed, the
residue, the gas borne particulate emissions, the quantity of fly ash, and the
3
economics involved in the purchase and use of these large machines.
A major need uncovered from these evaluations was the requirement for
more stringent air pollution control codes. The seven municipal incinerators
reported to the Incinerator Conference showed analyses of 4 to 17 times the
emission rate the EPA thought desirable, and ranged from a low of 0.30 to a
high of 1.35 grains. Most older incinerators are in this range, because of a
virtual absence of air pollution control equipment. EPA has established
particulate emissions of 0.08 grains per standard cubic foot of dry flue gas
corrected to 12% CO/,, as a standard to be met by "large" incinerators.
The potential for pollution has also existed for the land and the water
from large scale residue generation and large volume generation of scrubbing
and quenching water.
Another constraint to the construction of large scale incineration is in
the cost factors. Large incinerators, operating 24 hours per day, infer large
quantities of waste. This, in turn, means long hauls and increasingly expensive
transportation costs as part of the total picture required to generate such
quantities. Engineering and construction costs of the large plants, like all
major construction projects, have escalated tremendously in the past 20 years.
Mechanization and automation have sophisticated plant design and further
increased costs of design and construction.
The combustion designs of these large units almost universally incorporate
an excess air principle in the primary chamber to control the heat in the
emitted gas stream. This increased volume of air aggravates the problem of air
pollution control. Expensive and rather complicated pollution control devices
must be installed to control the emissions - either mechanical in nature; or
utilizing water washers or scrubbers. Due to the high expense, most large
scale plants have not yet installed such air pollution control equipment, and
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are being criticized accordingly for"their emission rates.
The combined effect of these capital cost elements has been that the
ownership and financing costs for the large plants range from 23 to 54
4
percent of the total operating cost structure.
Despite these environmental and cost problems that have faced municipal
incineration, many communities have felt that if different design approaches
were taken, incineration could be both environmentally and economically
feasible as a means of processing urban wastes. This has been based on studies
of the "small" incinerators that have been developed in recent years. Most of
these units are constructed in a factory, on a packaged basis. They have
burning capacities of from 500 to 3,000 pounds per hour. By utilizing
controlled air designs, and by using auxiliary fuel to burn off particulate
emissions, they are able to meet EPA's air pollution control recommendations.
While the majority of the small incinerators have been purchased by
industry and by institutions, for on-site destruction of wastes, during the
past five years an increasing number of municipalities have been investigating
their use. The sizes being considered have had charging rates of from 1,500
to 3,000 pounds per hour (processing rates of from 9 to 15 tons per day).
To provide the total burning capacity required by a municipality, the
system was developed of installing such units in modules of two to eight within
a single plant. Such a modular approach has provided greater site flexibility
for small and medium sized cities than exists with the large volume plants.
More importantly, it has provided flexibility for expansion as the city
expands its waste generation. Expanding communities can be put on a "pay-as-
you-go" basis, with lower capital investment than found in large incinerator
plants, and a consequent easing of tax burdens for capital repayment.
For certain larger communities, spread out over a large land area, the
modular plant approach has permitted the erection of relatively inexpensive
satellite plants. These have resulted in reduced hauling costs to the
incinerator from pick-up points or transfer stations.
The design standards of the small modular incinerators have proven that
they efficiently process residential and commercial waste. The volume and
weight reduction ratios are comparable to the large scale machines. With few
moving parts, maintenance problems, and hence costs, have been minimized. As
they do not employ water washers or scrubbers to achieve their low air emission
rates, or water quenching systems to cool the ash residues, the cost and
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environmental aspects from the use of water with large incinerators have
been eliminated.
Compared to large scale incinerators, the use of auxiliary fuel in the
smaller machines can create a cost problem. If the combustion engineering
has not been done efficiently, large quantities of such fuel could be burned
in order to achieve the desired air emission rates.
The use of automation has been kept to a minimum in the small incinerator
designs to keep down construction costs. Very few units have automatic ash
removal. Without this feature they must operate on a 24 hour cycle; the ash
residue must be removed by an operator after building up inside the chamber
for a given number of hours. The incinerator is normally cooled down to
permit this. This has a direct effect on the operation. It means additional
use of fuel to warm up the incinerator so it can be used once more. This, in
turn, results in thermal shock and some deterioration of the refractory, when
it is cooled and heated on a daily basis. As clean out of the ash is done by
hand, there is always the danger of damaging the refractory lining in the
process. As the ash is dry during clean out, it could be hot and potentially
dangerous for the operator. If done carelessly in a windy area, it could
create a dust cloud.
None of these design aspects are serious. Most have been solved in the
institutional and industrial fields, where the buyers have been agreeable to
spending additional sums to automate the equipment.
Many researchers have questioned the logic of destroying resources and not
obtaining every possible residual value from them. They have investigated
various possibilities of extracting such values from waste, at the source, at
some form of transfer station, or at an incinerator plant by burning the waste
as a fuel to create energy for the production of steam or electrical power.
Concurrent with the introduction of modular plants for municipal
incineration has been the introduction of waste heat recovery systems. These
systems directly produce steam in special boilers. The process as currently
marketed has proven to be efficient and economical, requiring only relatively
small amounts of auxiliary fuel (gas or oil) to start and maintain the process.
The net result has been to recapture the major costs of operating the
incinerator,through the sale of the steam produced.
During the present study, our surveys showed that many municipalities are
investigating the practicality of installing modular small incinerator plants
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to process their residential, commercial and some of the industrial wastes.
Originally, investigations by most communities concentrated on the advantages
of incinerators for volume reduction. During the past year, the emphasis has
switched to examining the potential advantages of the plant as a steam
producer for local industry or municipal use. Both approaches have been
covered in the report that follows.
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CHAPTER 3
REFUSE GENERATION
General
The incinerator units tested were specifically designed to burn municipal
waste. The designers and municipal sanitation officials have normally made
pre-installation estimates of the types and quantities of waste they will be
receiving from their residents in the foreseeable future; ranging from
residential refuse with an approximate heating value of 5,000 Btu per pound as
fired, to commercial refuse as low as 4,000 Btu, to industrial refuse that may
run well over 9,000 Btu per pound. Due to increasing amounts of paper and
plastic in the waste stream, the heating value of municipal waste has been
mounting steadily during the past ten years. The designers of the modular
municipal units have planned their systems so that they will handle waste
ranging from below 4,000 Btu per pound, to that rising over 9,000 Btu per
pound, in the mix that is charged each day, including moisture.
Cursory study of municipalities, combined with the detailed findings
from the present survey, reveals that it is difficult and often misleading to
generalize on both the quantities and characteristics of waste being generated
from one community to another.
The present study indicates that there are important differences between
communities. The total waste quantity generated per unit of population,
residency, or employment varies between communities in relation to their size,
social and economic make-up of the residents and workers as well as transients,
and the extent and type of commercial and industrial aetivity. Climate,
living styles, and seasonal variations also affect the quantities generated.
Make-up of the waste not only varies between communities but varies at
different days of the week and seasons of the year, within the same community.
Such variations in waste stream make-up have a definite affect on planning
for resource recovery, such as metal, glass and paper recovery, or the
production of steam from burning the waste.
The municipalities selected for detailed analysis in the present study
differ somewhat in their solid waste management, collection and reduction
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methods. From a systems aspect, the engineering of the municipal plants,
their specific operational methods, and the design of the various components
also vary from plant to plant to a degree.
While by no means representing a statistical sampling of such plants in
the U. S., the three communities selected for the present study do reveal
the solid waste problems found in many of the smaller and medium sized
communities. The survey methods and the results can be applied as a guide for
evaluating the use of "small" incinerator modular plants in hundreds of other
municipalities: from such aspects as waste generation quantities and types,
plant and equipment design and operation, environmental effect, and the
economics of capital purchase and operational costs, including resource
recovery.
Pahokee, Florida
Demography
The Town of Pahokee, Florida is a rural marketing center, incorporated in
1922, and now covers an area of five square miles. The population early in
1974 was 5,994 and is projected by the Palm Beach County Area Planning Board
at 6,400 by May 1975.
As of April 1974, dwelling units were projected at 1,864. Contributing
further to residential waste is one motel, one inn and five year-round
multi-dwelling units, with approximately 10 apartments each.
The waste from one 60 bed hospital is handled by the municipal facilities.
Educational facilities inqlude one elementary school; one middle school; one
junion-senior high school; and one private elementary school. There are eleven
churches and 20 clubs and organizations which include Lions, Rotary, Boy Scouts,
all of which send waste to the municipal facilities.
Generating commercial waste are seven sit-down restaurants; two fast
service establishments; one hardware store; five general merchandise stores;
nine food stores; two automobile dealerships; three used car lots; five gas
stations; five apparel stores; two furniture stores; two drug stores; and one
bank.
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The leading industry is sugar production with revenues that top $200
million per year. Food processing also encompasses potatoes, greens, and
other vegetables. Virtually all food production waste is processed within each
plant. Other industries include ice plants, chemical and fertilizer plants
and welding and machine shops.
Geographic Conditions
Pahokee is located on the southeastern shore of Lake Okeechobee. The
town is 45 miles west of West Palm Beach and 90 miles northwest of Miami. The
average mean winter temperature is 71 degrees F and the average summer
temperature is 81 degrees F. Pahokee's wet season begins in late May and ends
in late September. The average annual rainfall is 56 inches.
Operation of the Municipal Sanitation Department
Pahokee has a Sanitation Department operated under a Director of Public
Works and provides commercial and residential solid waste collection as well as
a municipally-owned transfer station and an incinerator plant. There is a
financial agreement with West Palm Beach County for use of the county landfill
located three miles from downtown Pahokee, or 1/2 mile from the town limits.
The county charges 30 cents per cubic yard for all hard fill and solid waste
non-combustibles (such as metals and glass) delivered to the landfill.
All combustibles are delivered to the incinerator plant, which was
installed and operational by May 1974. It was designed and manufactured by
Consumat Systems and contains two 8.5 ton per day Model C-550M incinerator
modules with automatic loaders, giving a total plant capacity of 17 tons per
10 hour day.
Residential collection is by a container-train which operates every other
day. Two sanitation men pick up from each residence by means of several
dnmpster carts pulled together behind a pickup. When full, the carts are left
at the transfer station. The waste appearing combustible is transferred to a
front loading compactor which, in turn, delivers full loads to the incinerator,
two to three times a day. Commercial collection occurs on the alternate days.
Combustibles, as well as small non-combustibles, are incinerated. Garden
waste over four feet in length, and large non-combustibles are hauled to the
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county landfill from the transfer station. The hospital delivers its
contaminated and pathological waste to the incinerator. Other wastes from the
hospital are picked up by the town on a commercial account. Four out of six
parks, within the town limits of Pahokee, have accounts with the town for
pickup of solid waste, excluding garden and non-combustible wastes which are
delivered to the county landfill.
Map 1 shows the relationsips of the solid waste management facilities.
a.
Map 1.
Pahokee Area
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Orlando, Florida
Demography
The City of Orlando was incorporated in 1875. Situated in Orange County,
Florida, it has a 1975 population of 120,000. The total area is 42 square
miles. Orlando has a diversified economy consisting of commercial
establishments, industries, manufacturing plants, motels, hotels, hospitals,
schools, and single/multiple occupancy residential areas. Construction of
motels and residences has been extremely heavy over the past five years. There
are 110 motels and hotels and 41,774 single and multiple households as of May,
1975. Generating additional wastes are seven hospitals totalling 3,000 beds,
37 primary/secondary educational institutions, and one junior college.
Commercial wastes are generated by 70 hardware stores; 41 general
merchandise stores; 164 food stores; 50 automobile agencies; 215 gas stations,
101 apparel stores; 105 furniture stores; 231 eat and drink restaurants; and
35 drug stores. Estimates for 1975 indicate total retail sales at
$1,025,068,000.
Orlando and vicinity has industries with a total of 155,300 wage earners
that produce waste for the Sanitation Department, including electronics,
aerospace, and food processing plants. The latter use large quantities of
potatoes and corn, but have in-house disposal-clarifying systems.
In five years, total daily solid waste generation per resident is
estimated to have risen from 4.5 pounds to 7 pounds, according to the
Superintendent of Refuse Collection. It is also estimated that motels and
hotels are now accumulating on "full" occupancy days as much as 5.5 pounds of
waste per day per room, but have large seasonal variations running from 100% to
40% occupancy. At present, due to a combination of climate (the wet and dry
seasons), plus the number of transients in the motels and hotels, there occurs
a total waste load variance as much as 100%: from 300 to 600 tons daily.
Geographic Conditions
Orlando is situated in a flat, sub-tropic area surrounded by 2,000 lakes.
Located 245 miles from Miami, 85 miles from Tampa/St.Petersburg, and 140 miles
from Jacksonville, in the center of Florida, the mean average temperature is
68 degrees F in the winter and 80 degrees F in the summer. The wet season
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begins late May and ends late September. The average annual rainfall is 54
inches. Conditions permit garden waste to be generated every month of the year.
Operation of the Municipal Sanitation Department
The Department of Sanitation handles the disposal of a daily average of
425 tons of solid waste. The Superintendent of Refuse Collection divides the
city into four collection districts—southeast, southwest, northwest, northeast-
for control of this operation.
Currently a transfer station is operated by Orange County nine miles due
west of downtown Orlando and used by the city for part of its waste load.
Long-range planning by the county and the city calls for five such transfer
stations to be established in the various quadrants of the city and county,
in order to reduce hauling costs. To date, only the western unit is in
operation.
The city transports its solid waste from the northwest quadrant to the
existing transfer station and is charged at a rate of $2.60 per ton by the
county. The transfer station has a maximum capacity for waste reception of
1,200 tons per day. After transfer to large county tractor-trailers, the waste
is then hauled to a County landfill area located 18 miles southeast across town.
Waste from the eastern half of the city is normally transported directly to
this same County landfill.
The southwest quadrant of Orlando is estimated to have a population of
approximately 30,000 and to contribute about one-quarter of the total community.
waste load. Due to the proximity of Disney World southwest of this quadrant,
this area has been expanding very rapidly with motels, hotels, light commercial
establishments and residences. Four years ago it was decided to install and
operate a municipal incinerator in the center of this quadrant to handle the
expanded waste generation.
The plant, completed in May 1974, contains eight identical Consumat
Model C-760M incinerators with L-518 automatic loaders. Each incinerator is
rated at 12.5 tons per 10 hour day, giving a combined total capacity of 100 tons
per day. The plant was designed to accept commercial, residential and some
industrial wastes. In addition, non-pathological waste is accepted from up to
three hospitals on the fringe of this sector.
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The collections are picked up from the generating sources in 20 yd.
compaction trucks and hauled directly to the incinerator. In practice, the
Sanitation Department controls the amount delivered to the incinerator plant
and "juggles" the truck routing. The maximum acceptable solid waste at the
incinerator is 105 tons daily. Any excess is sent to the transfer station.
If the day appears light in waste collected from the southwest area, waste
is brought from other quadrants or from fringe areas to level the load up
to the optimal 100 tons. Map 2 shows the solid waste management facilities.
Map 2
Orlando Area
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Siloam Springs, Arkansas
Demography
Siloam Springs was incorporated in 1880. Located in Benton County,
Arkansas, it has a population of 6,500, and covers an area of twenty square
miles. Its waste system is combined with the nearby town of Gentry to give
a total population served of 8,000. The combined area has a diversified
economy. Residential waste is generated by 2,376 homes in Siloam Springs
and an additional 500 homes in Gentry. There are no high rise condominiums
or multiple occupancy residential areas. Siloam Springs has six primary
educational institutions with 1,912 students, one university with 590 students,
one 80 bed hospital and six motels with 161 rooms generating wastes. Other
wastes are generated by 21 churches, several clubs and organizations which
include Lions, Rotary and Kiwanis, one medical clinic, five physicians, four
dentists and 105-bed nursing home. Gentry has a primary school and one 15
room motel.
Contributing to industrial waste in Siloam Springs are eleven industries
employing 1,628 people. These include a food canning plant, a process plant
for poultry, a chicken hatchery, and seven manufacturers that produce
automobile tires, telephone and communication cables, plastic pipe, steam
cleaners, cutting tools, wheel and brake drums, upholstered chairs, and
submersible motors. Gentry has a kitchen cabinet plant employing 86 people.
Commercial waste in Siloam Springs is generated by eight fast-food
service restaurants, six sit-down restaurants, two hardware stores, eight
general merchandise stores, ten food stores, five automobile dealers, five
used car lots, 25 gas stations, seven apparel stores, three furniture stores,
five drug stores and two banks. Gentry adds an additional 70 commercial
accounts.
Geographic Conditions
Siloam Springs is located in northwestern Arkansas, one mile from the
Oklahoma state line and 28 miles northwest of Fayetteville. The average mean
temperature in winter is 40 degrees F and in summer 84 degrees F. The area is
1,183 feet above sea level with an average annual rainfall of 58.4 inches.
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Operation of the Municipal Sanitation Department
The arrangement for operation of the plant and the municipal collection
of the solid waste is quite different in Siloam Springs from the other
municipalities examined. It represents a partnership between the municipality
and a local industry, an incinerator plant designer and manufacturer, and a
distributor of the equipment and systems. This came about as a result of the
current energy shortage in the U. S., and pressures to locate alternate
sources for energy, combined with the community's desire to improve its solid
waste management.
A major manufacturer and Siloam Springs employer, the Allen Canning
Company, requires substantial quantities of steam for its food processing
operations. Its direct-fired boilers use natural gas, which has almost
tripled in price during the past two years; there is also the possibility of
gas rationing. The company was agreeable to placing a long-term contract for
the purchase of steam from the municipality, at rates tied to the going price
of such energy, providing a satisfactory supply could be developed. The
municipality, anxious to maintain full employment in the community, completely
agreed with the concept.
The town, like many others, had been faced with solid waste management
and disposal problems. The soil in many parts of Arkansas is rocky and
presents difficulties for operating sanitary landfills. Waste loads have been
increasing with population and commercial growth, as have the disposal costs
per ton. Further, many members of the Town Council felt that the wastes being
generated represented too valuable a resource to be simply destroyed by
incineration or buried in a landfill. If incineration with waste heat energy
recovery could be efficiently combined, it would appear that both industry and
the town would benefit.
Allen Canning Company agreed to lease a plot of land, adjacent to its
plant, to the city for $1.00 a year, on a twenty year lease with renewals, for
construction of an incinerator plant with a steam recovery system.
The town agreed to provide funds to purchase the necessary equipment and
systems, including the plant structure and site improvements.
When the entire technical, operational and financial package was put
together, it,was projected that the income from the sale of steam, coupled with
that from waste collection fees, was sufficient to cover all operating costs
and liquidate the capital investment over a sixteen year period. The city was
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able to sell bonds at a relatively low interest rate, to finance the complete
investment. Appendix E contains the complete Agreement between the town and
the canning company.
The first phase of plant construction consists of a 21 ton per 10 hour
day plant with two 10.5 ton per day Model C-550MS Consumat incinerators with
automatic loaders. The incinerators are connected to waste heat recovery
boilers. Initial steam production is guaranteed to be a minimum of
120,000 pounds in a 12 hour day at 100 psig. The boiler steam output is
piped through an insulated line approximately 450 feet, across a street and
into the steam supply system of the Allen plant. Operation of the system
commenced in June 1975-
All commercial and residential waste generated by Siloam Springs and
neighboring Gentry is collected under a contract management system and trucked
to the incinerator plant. The city collects the waste fees for the service
from the residents and commercial establishments. The arrangement is now being
broadened to include wastes from certain industrial plants.
The incinerator distributor was given a management contract for at least
the first two years of operation of the incinerator-steam plant, to ensure
technical efficiency in its initial operation. The city also established, by
ordinance, a Sanitation Facilities Commission to act as liaison between the
City Council and the management of the waste disposal and energy production
system.
The city has a landfill and has retained it for the disposal of large
items that are non-combustible, or that might cause problems in the incinerator
operation, either due to their size or chemical nature (such as cans of lacquer
thinner). At present, the landfill is also used for disposal of the
incinerator ash residues. In the future, these residues may be stockpiled and
used for road repairs.
Under the present contractual arrangement, waste collection is managed by
the incinerator plant supervisor utilizing a driver foreman and six laborers.
Collection of solid wastes is bi-weekly utilizing three compactor trucks
with the town divided into two collection districts. Combustible waste is
delivered directly to the incinerator from the pickup points. Bulk items and
non-combustibles go directly to the landfill.
Gentry and Siloam Springs have ordinances that require curbside pick-up.
Kitchen waste, leaves, grass, small yard trimmings, shrub and tree trimmings
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less than 2 inches thick, waste paper, cans and glass must all be placed in
plastic bags or tied in bundles no larger than 4 foot square and weighing no more
more than 50 pounds. Large tree trimmings over 2 inches thick, large
non-combustibles (such as metal parts and appliances) are collected on special
request by the town and taken to the landfill.
Map 3 shows the solid waste facilities of Slloam Springs.
n
Map 3
Siloam Springs Area
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CHAPTER 4
TECHNICAL DESCRIPTION OF EQUIPMENT AND PLANTS
In each of three plants tested, the incinerators were factory engineered
and constructed, and shipped to the sites as pre-packaged systems. All three
plants were modular in design, housing from two to eight units to achieve the.
desired plant size and total processing capacity. The major differences
between the plants consisted of building design and plant equipment (such -;>
scale house), size of plant floor and building, charging mechanisms and
controls, and energy recovery systems. Minor differences were in the
auxiliary fuels (natural gas, propane gas, or oil) used. At each plant, the
incinerators operated on basically the same controlled air principles as
discussed below.
Theoretical Considerations
The design of each of the tested incinerators is based on the controlled
air principle. Two refractory lined and insulated chambers, designated
primary and secondary, are used for the combustion process, and a refractory
lined stack is used to duct the exhaust gases to the atmosphere. The waste
is charged into the primary chamber where ignition takes place. Once pvcsrt-
conditions of temperature and time have been achieved, the primary chamber
auxiliary fuel burners are turned off automatically.
A reducing atmosphere (insufficient oxygen for complete combustion) is
maintained in the primary chamber and the gas velocity is kept very low to
minimize the entrainment of particulates in the effluent gas stream. 'in is
gas is introduced into the secondary chamber through a zone of turbulent
airflow where the combustion process is completed. An oxidizing atmn^prete
(excess air) is maintained in the secondary chamber to insure complete
oxidation of the combustible material in the gas. The effluent from the
secondary chamber flows into the stack through an air induction secti>•<.-. Th;.1
inducer serves to cool the hot gas stream prior to its exit from the •v'affyn.
The unit operates at a slightly negative pressure which insures that any
infiltration is directed into the system.
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The operating regime of both the primary and secondary chamber is shown
schematically in Figure 1. The curve shows a characteristic combustion gas
temperature variation as a function of air-fuel (waste) ratio. Starting in
the reducing region (insufficient oxygen), the temperature will increase as
the air-fuel ratio is adjusted toward the chemically correct mixture
(stoichiometric).
a.
s
CO
Z3
CD
O
O
REDUCING
ATMOSPHERE
( PRIMARY
y CHAMBER
OPERATING
RANGE
OXIDIZING ATMOSPHERE
SECONDARY CHAMBER
OPERATING RANGE
STOICHIOMETRIC
AIR/WASTE RATIO
Figure 1. SCHEMATIC OF DESIGN TEMPERATURE OPERATING RANGE
The maximum temperature is attained at a ratio near the stoichiometric value.
The operating range of the primary chamber is superimposed on the curve in the
reducing region. As the air-fuel ratio moves into the oxidizing region (excess
air), additional air serves only as a dilutent and the gas temperature is
reduced. The operating range of the secondary chamber is superimposed on the
curve in the oxidizing region for illustration purposes.
The relationship between the physical parameters of the system (the
volumes and areas involved, and operating parameters; the operating
temperatures, burn rate and gas flow rates) are important in designing for high
performance in terms of maximum destruction rates, minimum emission rates, and
equipment reliability. The general simplified relationships are shown
schematically in Figure 2.
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o
o
CO
Tgas = Constant
Tgas = Constant
Tgas = Constant
BURN RATE
A. PRIMARY CHAMBER GAS
VELOCITY
GAS VELOCITY
B. ENTRAPMENT VELOCITY
PARTICLE SIZE
C. RETENTION TIME
REQUIREMENT
Figure 2
SCHEMATIC OF DESIGN PARAMETER RELATIONSHIPS
Figure 2. Curve "A" shows the variation of gas velocity with burn rate
for a constant gas temperature and fixed equipment sizing. The effect of gas
velocity on emissions is illustrated in Curve "B". This curve shows that the
higher the gas velocity, the larger the particles which can be entrained in
the gas stream. The effect of particle size on design is shown in Curve "C".
This shows that the larger the particle size, the greater the retention time
required for complete combustion. Taken together, the curves indicate the
need to balance the design burn rate (gas velocity) with the secondary chamber
volume to insure that sufficient retention time is available to completely
burn the particles which can be entrained in the effluent gas stream.
Design Considerations For The Incinerators
The theory just described is translated into practice only through
properly designed equipment and integrated systems and controls. The nature
of municipal incineration dictates the necessity for rugged construction and
simplicity of operation. The environmental standards that must be met under
current EPA recommendations, as well as state and local codes, dictate the
necessity for proper loading and properly controlled temperatures to ensure
minimal particulate emissions.
The general designs of the incinerators that were tested are shown in
Figure 3 for Pahokee, Florida; Figure 4 for Orlando, Florida; and, Figure 5
for Siloam Springs, Arkansas.
In each case, it will be noted, the incinerators had many points in common
for the primary and secondary chambers and stack sections. All the
incinerators employed automatic loaders, hydraulically operated with a ram
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feeder, and remotely controlled by the operators of the loading vehicles that
moved the waste from the plant floor to the loader. Figure 6 illustrates the
automatic loader sequence at Pahokee, and Siloam Springs, while Figure 7 shows
the sequence used at Orlando.
Batch-fed municipal units of this type have five basic modes of operation:
warm-up, charging, burn-down, cooling and clean-out. All such units can be
charged at a greater rate than the waste can be burned. The waste in the unit
at the end of the charging day is consumed during the burn-down period. (This
type of operation is not to be confused with continuous charging, 24 hours/day,
where the charge rate and burn rate are equal and the ash is removed
continuously).
Because incinerators of this design operate with auxiliary fuel, they have
automatic controls to regulate the amount of fuel used. These involve
strategically placed thermocouples to record temperature fluctuations within
the two chambers; valves to control the flow of auxiliary fuels and dampers to
control air (oxygen) inlet. They also utilize a sequence timer to
automatically shut off the burners within a set time duration (usually three
hours) after the last charge: - the timer is set by each closing of the loader
fire door, continually resetting until loading ceases.
The primary chamber blower continues to operate after the burners shut off,
unless the power is turned off. This is done to assure complete burn-down and
to help cool the primary chamber before clean-out the following morning.
Obviously, for good waste reduction and environmental effect, temperatures,
pressures, and air control are critical. Ideally, to minimize fuel consumption,
operating temperatures should be arrived at rapidly. By a combination of
auxiliary fuel injection and air control, during warm-up the temperature in the
primary chamber rises to approximately 1400 F and in the secondary to'
approximately 1800 F. The controls maintain the proper mixes of air and
auxiliary fuel, combined with the heat output of the burning waste, to retain
these temperatures during the charging and burn-down periods.
The primary chambers of the tested units were equipped with water spray
systems to control temperatures. The spray nozzles are protected from the
usual operating temperatures by a constant drip of water through the system.
The sprays are automatically actuated when temperatures in the lower chamber
exceed preset conditions.
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The materials of construction for such pre-packaged units have to lend
themselves to the economic advantages of manufacturing in a factory, yet must
be able to take the abuse as well as heavy duty use that is experienced in
municipal operations. The outer shell and end domes in the test units were
fabricated from 1/4 in. steel plate. All weight loads were carried through
bulkheads formed from heavy structural steel channel and T-beams. The primary
and secondary chambers and the stack sections were fully lined with castable,
high temperature refractory, as was the full-swing end dome, and this was, in
turn, backed up by mineral block insulation to minimize heat loss. Because
clean-out was performed in the test units by long rakes mounted on tractors,
the refractory in the primary chamber suffers considerable abuse. The lower
section of this chamber was, in each case, lined with firebrick to reduce the
erosion from clean-up.
The control panels and contactor boxes were mounted remotely from the
incinerator, within the plant building adjacent to each loading platform.
Pendant boxes were also located at the door to the loading platforms so that
the operators can activate the automatic chargers without leaving their
vehicles.
Burner safety controls, for each unit, appeared well designed, and the
gas-fired models met code requirements.
The designs have been simplified to the point where maintenance
requirements are quite minimal; such as lubricating latches and hinges on the
doors; checking the blower intakes for foreign matter; visually checking for
gas or fuel leaks, cleaning the air ports and air plenum holes, and cleaning
the spark igniters and flame sensors monthly. The hydraulic loaders require
normal visual checking daily and weekly for lubrication and hydraulic fluid
levels. If waste heat boilers are included then the boiler tubes should be
visually checked at least weekly.
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o
o
a:
O
a:
UJ
2
o
z
3
2
in
UJ
•H
tu
-26-
-------
O
O
z
(E
O
<
-------
-------
HOPPER OPENING
RAM
|—FIRE DOOR
** -HOPPER OPENING
I
1
•RAM
. Waste loaded into loader chute.
2. Fire door opens.
\
—FIRE DOOR
|— HOOPER OPENING
L
3
L
RAM
3. Ram comes forward.
V
,-FIRE DOOR
I I—HOPPER OPENING
L
L
RAM
4. Ram reverses to clear fire door.
\T
HOOPER OPENING
I-RAM
FIRE DOOR
5. Fire door closes,
\
HOPPER OPENING
RAM
6. Ram returns to start position,
Figure 6. AUTOMATIC LOADING SYSTEM, PAHOKEE, AND StLOAM SPRINGS
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\_[
FIRE DOOR
r
HOPPER OPENING
1. Waste loaded into loader chute.
\
V
J— FIRE DOOR
r
HOPPER OPENING
L
RAM
2. Left unit fire door opens.
\
— FIRE DOOR
i—
HOPPER OPENING
3. Ram pushes waste into left unit.
A
J — FIRE DOOR
i-
HOPPER OPENING
LRAM
Ram returns to clear fire door.
\
FfRE DOOR
RAM
rr
p
r
HOPPER OPENING
5. fire door closes, ram is in
position for charging right unit.
\
\
Figure 7, AUTOMATIC LOADING SYSTEM, ORLANDO, FLORIDA
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Design of Steam Production Systems
With the diminishing supplies of fossil fuels, the increasing cost of
energy production, and the increasing cost of operating conventional
incinerators, serious investigation commenced on the potential of using
solid waste as a fuel to produce energy, in the form of steam, during the
incineration process. The idea is not new. In Europe, solid waste has been
used for several years as a fuel for producing steam, with varying degrees of
efficiency.
One approach has been to augment fossil fuel (coal) with a percentage
of the milled combustibles from the solid waste stream in firing conventional
boilers for the production of steam for turbine generation of electricity.
Another approach has been to convert the primary chamber of a conventional
incinerator into a boiler. This is known as "waterwall incineration".
Vertically arranged boiler tubes, joined by metal fins, are mounted to the
refractory lining of the incinerator. Energy from the combustible segment of
solid waste is absorbed by the water passing through the tubes and converts
the liquid to steam. A major problem found in the process arises from the
fact that conventional incinerators produce a relatively contaminated gas.
The boiler tubes become coated and corroded from the chemicals and metallics
in the gas stream.
We have pointed out in Chapter 2 that conventional incineration,
employing excess air in the primary chamber to reduce the heat in the gases
emitted during combustion, produces a much more contaminated gas than results
from controlled air machines. Also, the temperature relationships are
different between the two designs. To meet air pollution control codes,
conventional incinerators must (or should) install mechanical, or water
operated, devices to treat the emitted gases. These devices also drastically
cool the gas stream. Any heat extraction for energy recovery must take place
before the gas enters the pollution control devices: either in the primary
chamber, or in a close-coupled secondary chamber.
The new controlled air incinerator designs are not faced with these
constraints. The corrosive elements and particulates, including metallics,
are considerably reduced in the gas stream by the high temperatures in the
secondary chamber (after-burner), due to the use of auxiliary fuel, and
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without the use of mechanical pollution control devices. Hence, the energy
conversion systems that have been developed for use with these incinerators
have utilized the hot gas stream exiting from the after-burner chamber as the
fuel to operate a packaged boiler installed adjacent to the incinerator.
Theoretically, this cleaner fuel should provide more efficient and longer
boiler tube life than found in conventional incinerator designs.
The controlled air incinerators installed at the Siloam Springs plant are
connected to steam boilers fueled by the gases emitted from the after burners
in this manner. The incinerator modules in the system are similar to those
used in Pahokee and Orlando, with a primary chamber operating on reduced air
and a secondary chamber operating on excess air. The difference in design is
that the gases exiting from the secondary chamber can either be exhausted out
the main or "dump" stack, or can be diverted through the tubes of. a waste
heat recovery boiler and out a secondary stack. Figure 8 illustrates the
arrangement used.
By utilizing two stacks and a system of aerodynamic valving, the system
is quite flexible. The flow of exhaust gases from the secondary chamber can
be automatically shifted in three different directions — up the main, or dump,
stack when steam production is not desired; across, into and through the waste
heat recovery boiler for steam production; or the flow can be divided between
these two routes when only partial heat extraction is desired. Figure 9
illustrates this control system.
As a safety feature, in the event of a power or control failure, or excess
pressure in the boiler, the gases are directed up the main stack.
Waste is charged and burned in the primary chamber in the same manner as
in incinerators without the waste heat recovery feature. However, in the
waste heat recovery system the controls for air and auxiliary fuel and
temperature sensing are more sensitive and efficient. This results in lower
gas velocities in the main chamber, a more complete oxidation process in the
secondary chamber, and lower stack emissions.
Other designs using the emitted gases to heat boiler tubes in this manner
have incorporated mechanical valves to direct the flow and these have
experienced operational and maintenance problems from the high temperature
environment. The Siloam Springs system, by using aerodynamic valving appears
to have avoided this. It also has provided excellent response time, dropping
from full steam production to zero in less than 10 seconds. The aerodynamic
-32-
-------
valving incorporates a jet pump design, with momentum exchange, lowering the
static pressure to shift the direction of gas flow.
For such energy conversion systems to be feasible there must be a
nearby customer, agreeable to buying all the steam the system will produce.
The practical limit for piping steam is under one mile. Obviously, the
system is more efficient if it employs a condensate return.
As waste heat recovery is performed as a substitute for burning fossil
fuels in direct fired boilers, it must be economically feasible. The boiler
should operate in the same efficiency range as a direct fired boiler, with
auxiliary fuel consumption minimized so that there is a net savings in the use
of fossil fuel over a direct fired boiler producing the equivalent amount of
steam. Steam production should be continuous and of good quality.
Obviously, municipal waste is not as efficient a fuel as any of the
fossil fuels - coal, oil or gas. It has a far lower Btu output per pound
in its average "as received" condition and therefore greater weights
must be burned to produce energy equivalent to fossil fuels. It has not the
compactness of fossil fuels and, therefore, far greater volumes must be burned
to produce energy equivalent to fossil fuels. The "as received" condition of
municipal waste contains a high percentage of non-combustibles and a great
deal of moisture, neither of which contribute to the production of heat
(energy). Only the dry combustible portion can be useful in steam production.
All these factors must be considered in calculating the efficiency of a
waste heat recovery system (as seen in Chapter 15). The incinerator design
must be capable of accepting a wide range of waste composition, with Btu output
that varies from charge to charge, and still produces satisfactory steam at the
pressures and volumes required by the user. Appendix B presents the lower
heating values of typical products found in municipal waste streams, and
illustrates the complexity of the waste heat recovery design problem. The
boiler design, the incinerator air and auxiliary fuel controls, and the
combustion system must be well-engineered and well-matched if the boiler
efficiency is to be comparable to direct fired units using fossil fuels.
-33-
-------
SECONDARY STACK'
DUMP STACK
SECONDARY
COMBUSTION
CHAMBER
PRIMARY
COMBUSTION
CHAMBER
Figure 8. GAS FLOW IN STEAM PRODUCTION SYSTEM
SILOAM SPRINGS, ARKANSAS
-------
Figure 9 shows how the waste heat
energy system operates. Two
stacks are provided to give the
system a wide range of
operational flexibility. The
large stack is used to operate
the equipment as an incinerator
only. The smaller stack carries
the flow when the system is
producing steam. Partial heat
extraction can be maintained
by dividing the flow. This
flow control is maintained by
a patented aerodynamic valving
arrangement.
In the event of a power
failure or control failure
the system will immediately
direct the hot gases through
the dump stack. Once the
incinerator is operating,
this rapid response feature
will control the system from
full steam production to zero
in less than ten seconds.
This results in capital
savings by eliminating the
need for a condenser or other
heat dissipating device.
The aerodynamic valving
also eliminates the need for
mechanical valving in either
stack, reducing maintenance
costs.
NO HEAT
POWER OR
CONTROL FAILURE
FULL LOAD
PARTIAL LOAD
Figure 9.
CONTROL SYSTEM FOR GAS FLOW
SILOAM SPRINGS, ARKANSAS
-------
Design of Plant and Buildings
The general engineering design of all the plants surveyed was fairly
similar. They consisted of steel prefabricated buildings, raised approximately
six feet from ground level, with the interior floor a concrete flat slab,
sloped to floor drains to permit high pressure hosing and other good
housekeeping practices. In each case, the building is approached by the waste
trucks from a drive-in entrance, with a ramp of approximately 10 degrees
leading from the driveway and into the building.
The waste is deposited, by truck loads, on the plant floor, adjacent to
the loading platforms that lead to the incinerator charging boxes. The
incinerator modules are mounted on concrete pads and on a lower level to permit
the loading vehicles to scoop and push the waste from the plant floor onto the
loading platform and allow full front bucket loads to drop into the receiving
boxes of the automatic ram chargers.
The Pahokee and Siloam Springs plant buildings are square and the two
incinerators are placed at the end of the building opposite the truck entrance.
The plants are rated 17 tons and 21 tons, respectively, per 10 hour day. (See
Figures 10 and 11 and photographs on pages 39 to 43). The 100 ton plant at
Orlando consists of eight furnaces. The building is a rectangular structure
120-ft. by 180-ft. Four modules are located, in pairs, with common loaders
between them, on each of two sides of the building. (See Figure 12 and
photographs on pages 45 to 46). In this plant the waste trucks drive through
the building and exit the opposite side.
As can be seen from the photographs on page 42, the addition of the waste
heat recovery boilers to produce steam at the Siloam Springs plant resulted in
a modified architectural design of the building. At the other two sites the
incinerators are set on open pads with no roof, or other protection from the
weather around them. At Siloam Springs, the incinerators are completely
enclosed to protect them and the steam boiler equipment from the weather; the
stacks protrude through the roof. Large overhead doors are cut into the
building at each side to match the ash removal doors of the incinerators.
It would appear that enclosing the incinerators offers an improvement
in plant design, preventing weathering of metal shells and reducing maintenance
costs.
-36-
-------
The steam boilers are above the level of the secondary chamber,
elevated about 12 feet above the plant floor. This is accomplished in the
Siloam Springs plant by installing a welded steel balcony over the
incinerators to hold the boilers, together with all accessory equipment, such
as feed water storage tank and steam separator, water conditioner, air
compressor and tank for boiler tube blow down, and the various gauges and
control panels.
Each plant contains an office, washroom facility and storage area to hold
tools, spare parts and maintenance supplies.
In each case, the plants are located on plots that are fenced,
attractively landscaped and are well maintained.
At Orlando and Pahokee the residue is carried to and spread on a plot on
the plant site. At Siloam Springs, it is hauled to the municipal landfill.
-37-
-------
DESIGNED CAPACITY
17 TONS PER DAY (10 HOURS)
WASH
ROOM
ENTRANCE
RAMP
TIPPING FLOOR
CONTROLS
CONTROLS
D
ASH /
REMOVAL (If,
l-M V
PAD ] >
. I
1
L
\ ,
g _j h c •
T ~
— — — — — — —
\
ASH
REMOVAL
PAD
Figurt 10
MUNICIPAL INCINERATOR PLANT
PAHOKEE, FLORIDA
-38-
-------
Pahokee is typical of the design of
modular small incinerator plants servic-
ing communities of under 10,000 population.
The two 8.5 ton per day incinerators are
installed on pads at the rear of the
building below the level of the plant
floor to permit gravity loading of the
charging hoppers.
Photograph 1
PAHOKEE^ FLORIDA
Pahpkee, Florida has a
plant rated at 17 tons
per 10 hour day. It is
constructed from a pre-
fabricated building,
raised above ground level
on a concrete slab,
which forms the flat
tipping floor for the
waste deliveries by the
compactor trucks.
-39-
-------
A front loading tractor
alternates the charges
to the incinerators at a
rate of one to each unit
every eight minutes.
Scooped from the waste
pile on the tipping
floor, a load is pushed
to the entrance chute
platform, from which it
drops into the hopper
and is ram fed into the
incinerator.
The hopper cover opens
to receive the waste
when the driver activ-
ates a pendant switch
hanging in the doorway
to the loading platform.
As the driver backs into
the plant floor, he
activates a second
switch, which closes the
hopper cover and ener-
gizes the ram that
charges the load into
the incinerator.
Photograph 2
PAHOKEE, FLORIDA
-40-
-------
DESIGNED CAPACITY
21 TONS PER DAY (10 HOURS)
STEAM PRODUCTION
10,000 LBS/HR.
ASH REMOVAL
PAD
ENTRANCE RAMP
-STEAM LINE TO
ALLEN CANNING CO.
OFFICE
CONTROLS
TIPPING FLOOR
BALCONY A STEAM
BOILERS
STORI
ROOM
CONTROLS
ASH
REMOVAL
PAD
Figure
MUNICIPAL INCINERATOR PLANT WITH STEAM BOILER
SlLOAM SPRINGS, ARKANSAS.
-------
Siloam Springs has
installed a 21 ton per
day plant. Energy
recovery from incinerat-
ing the municipal waste
produces steam at the
rate of 120,000 pounds
for a 12 hour day.
The photograph shows the
insulated steam line as
it exits the front of
the building. The can-
ning company that pur-
chases the steam is
located directly across
the street.
In this plant both of
the 10.5 ton per day
incinerators are en-
closed by the building.
Large overhead doors
permit complete opening
of the units-for ash
removal.
Steam production equip-
ment is installed on a
balcony above and be-
tween the two incinera-
tors.
Photograph 3
SILOAM SPRINGS,ARKANSAS
-42-
-------
When the gases from the
secondary chamber are
diverted through the
waste heat boiler they
enter at around 1800°F
and exit at less than
350°F. The steam is
generated $41 excess of
100 psig and at a rate
of 5,000 pounds per hour
from each boiler. This
equals the production of
an in-house boiler at
the canning plant. The
average efficiency of
the waste heat boiler is
70%.
A front loading tractor
feeds the two incinera-
tors at Siloam Springs.
Photograph 4
SILOAM SPRINGS, ARKANSAS
-43-
-------
DESIGNED CAPACITY
100 TONS PER DAY. ( 10 HOURS)
I J
L_
Figure 12
McLEOD RD. MUNICIPAL INCINERATOR PLANT.
ORLANDO, FLORIDA
-44-
-------
The 100 ton per day
plant at Orlando,
Florida is typical of
the larger modular muni-
cipal incinerators. It
handles one quarter of
the waste generated by
this 120,000 population
£ community.
The construction and
landscaping ensure that
good community relations
are maintained. The
plant is attractive and
clean, with environment-
al problems eliminated.
The incinerators are
installed in pairs on
the periphery of the
building. A common
loader charges each
pair.
Photograph 5
ORLANDO, FLORIDA
-45-
-------
The Orlando Municipal Incinerator plant
is attractive in appearance yet the
design is simple and functional.
Utilizing a steel prefabricated build-
ing erected on a raised concrete slab,
capital cost is kept quite low. The
open construction allows ease of plant
cleaning.
Photograph 6
ORLANDO, FLORIDA
-46-
-------
CHAPTER 5
PLANT OPERATION SYSTEMS
Each plant uses similar systems for receiving waste, charging the
incinerators and removing the ash residue. The main differences between
plants are in their capacities, in architectural design and in staffing
patterns utilized.
Orlando is the only one of the three plants that has its own truck scale,
with automatic recorder-printer and scale house. Admittedly, this is not an
inexpensive accessory for a municipal plant. However, the use of a scale is
the only satisfactory method for maintaining an accurate record of the net
weights of waste and burned each day. Without such daily records it
is nearly impossible for the plant owners to determine the efficiency of a
plant, as virtually all calculations must tie into the weight of waste handled
and the ash residue removed. Further, if charges to customers are based on
weight of waste received, a weigh scale is essential.
Orlando, as the largest capacity plant, has the largest staff - plant
supervisor, secretary-bookkeeper, shed foreman, four tractor operators, a
skilled laborer and a laborer who is also the residue truck driver - a total
of nine. Siloam Springs utilizes a combination plant supervisor-boiler
operator and two laborers. Pahokee employs a plant supervisor and a laborer
and pays for part of the Public Works Director's salary to cover office
assistance.
Compared to the large incinerator plants these would appear to be large
labor forces for the tonnage of waste handled. However, as the plants are not
automated for sorting, shredding or charging the waste into the loading
hoppers, these appear to be the minimum labor figures to permit efficient
daily operation and maintenance.
The bulk of the waste is delivered onto the plant tipping floor in
compactor trucks and dumped into piles adjacent to each loading platform that
leads to the charging box of an incinerator. At Orlando this normally is
placed into four piles, each feeding two incinerators that have a common
charging box and reciprocating ram between them. At the other two plants
both machines are normally fed by a single pile placed between them.
-------
The normal operation is for a tractor operator, using the front loader,
to scoop a full load of waste from a pile and push it onto the loading
platform. When the pile on the platform is approximately three hundred
pounds in weight (roughly a cubic yard in size) the tractor operator
energizes a pendant mounted push button switch to open the door of the
charging box, pushes the entire load off the end of the loading platform,
dropping it into the charging box. As he backs out of the platform he pushes
another switch in the pendant that closes the feed box door and activates the
ram mechanism.
The charging is normally signalled for by the incinerators themselves,
based on their heat sensing, and a red light calling for a charge. On an
average, depending on the model, each machine is charged from six to eight
times per hour. The operator alternates his charges between two units.
The incinerators are normally charged from seven to ten hours per day.
They then continue to burn down for approximately three hours more, at which
point they cool down until the next morning.
Ash residue removal takes place as soon as each plant opens in the
morning and is done by one operator using a tractor with a long ash "rake"
attached to the front end. After the module has been emptied onto the ash
platforms in front of it, it is then ready for the day's burning operation.
After a few minutes cooling time the tractor operator removes the ash from
each platform, either by front loader or into a dump truck. Should it be
determined that the ash requires further cooling before hauling, water is
sprayed on it by an ordinary garden hose.
Once the incinerators have come up to heat, solid waste that has already
been dumped on the plant floor is charged into each incinerator unit.
The floor of the shed is kept clean by hosing it down constantly, and at
the end of the day, the entire plant is swept and hosed down. As a result
of excellent housekeeping practices, there is little odor in any of the plants.
The flow diagrams in Figure 13, 14 and 15 show the difference in systems
design at each plant.
-48-
-------
FURNACE
(TOTAL OF 2)
FOR EACH
FURNACE
ATMOSPHERE
A
i
STACK
A
SECONDARY
EXHAUST GAS
BURNING CHAMB.
A
PRIMARY
WASTE
BURNING CHAMB.
>
*
^.
_> -
s~
RESIDUE
REMOVAL BY
TRACTOR RAKE
V
RAM CHARGER
TRACTOR
MOVERS
QUENCH WATER
FROM HOSE
DUMP TRUCK
LOADING.
WASTE
FEED PILE
PRIVATE
TRUCK WASTE
DELIVERIES
Figure 13.
I
TEMPORARY
."J TRUCK SCALE \
! FOR TESTING I
n
MUNICIPAL
COLLECTION
SYSTEM
FOR SOLID
WASTE
SOURCE
FLOW
SAMPLING
POINT
SOLID WASTE AND RESIDUE
GASES AND PARTICULATES -
FLOW DIAGRAM FOR PAHOKEE MUNICIPAL INCINERATOR
-4Q-
-------
FURNACE
(TOTAL OF 8)
RECIPROCATES
BETWEEN 2
FURNACES
ATMOSPHERE
A
i
STACK
A
SECONDARY
EXHAUST GAS
BURNING CHAMB.
A
PRIMARY
WASTE
BURNING CHAMB.
RAM CHARGER
TRACTOR
MOVERS
RESIDUE
REMOVAL BY
TRACTOR RAKE
QUENCH WATER
FROM HOSE
A
DUMP TRUCK
LOADING.
PRIVATE
TRUCK WASTE
DELIVERIES
Figure 14.
WASTE
FEED PILE
TRUCK
SCALE
MUNICIPAL
COLLECTION
SYSTEM
FOR SOLID
WASTE
TRUCKS
LOADED a
EMPTY
SOURCE
FLOW
SAMPLING
POINT
SOLID WASTE AND RESIDUE
GASES AND PARTICULATES ._
FLOW DIAGRAM FOR ORLANDO MUNICIPAL INCINERATOR
-50-
-------
FURNACE
(TOTAL OF 2)
<
FOR EACH
FURNACE
ATMOSPHERE
ATMOSPHERE
A
A
/t\
*
STACK
STACK
A
A
SECONDARY
EXHAUST GAS
BURNING CHAMB.
_ _\ _
A
PRIMARY
WASTE
BURNING CHAMB
RAM CHARGER
TRACTOR
MOVERS
RESIDUE
REMOVAL BY
TRACTOR RAKE
QUENCH WATER
FROM HOSE
STEAM
PURCHASER
STEAM
BOILER
/
*v
r
TREATED
FEED WATER
WASTE
FEED PILE
PRIVATE
TRUCK WASTE
DELIVERIES
TRUCK SCALE '
i FOR TESTING
I !
A
MUNICIPAL
COLLECTION
SYSTEM
FOR SOLID
WASTE
SOURCE
FLOW
SAMPLING
POINT
SOLID WASTE AND RESIDUE jl
STEAM PRODUCED ....:>...
GASES AND PARTICULATES —>
gure 15.
FLOW DIAGRAM FOR SlLOAM SPRINGS MUNICIPAL INCINERATOR
-51-
-------
CHAPTER 6
THE TESTING PROTOCOL
The testing and evaluation of any incinerator system is done with the
following objectives in mind:
1. To determine the efficiency of the incinerator system as a
solid waste reduction device, in terms of the volume and weight of
the waste processed in the system and the residue remaining
2. To determine the pollution load released to the environment, in
terms of the quality and quantity of gaseous, solid and liquid
effluents released during incineration.
3. To determine the operating, maintenance, ownership, and
financing costs.
4. To determine the limitations of the system in terms of
processing the solid waste stream that is normally delivered;
to completely characterize its operation on a day-to-day
basis; and to evaluate the effects of the system's design, as
well as operational variations, on its intended performance.
5. To characterize the "as received" solid waste to determine
the moisture and Btu content.
6. In the case of small incinerators of the controlled air
design, to monitor the use of auxiliary fuel and consumption of
power.
7. Where the system incorporates waste heat recovery through steam
production, to determine the efficiency of the design and its
economic feasibility.
The majority of the work in such testing can be performed at the
incinerator site followed by laboratory analysis of samples. This means a
logistic plan for testing prepared well in advance of the test period; with
the installation of instrumentation, measuring devices, weighing devices, and
the utilization of plant space in a manner that permits accurate testing with
as little interference as possible to the normal day-to-day operation of the
plant. It also infers that the plant management has maintained adequate and
-52-
-------
accurate records involving such matters as fuel and utility consumption,
capital and operating costs, incoming waste weights, reduction efficiencies,
residue weights and volumes and other operating criteria, for a sustained
period before the test and evaluation period takes place. This will permit
comparisons and correlations between the data found during the test period
and the long run data maintained by plant management.
Any incinerator plant is a mass production installation and space is
normally at a premium. For a testing situation, conditions are not always
ideal. Occasionally, compromises will have to be made, but they should
always be considered and carefully studied to ensure that they do not overly
influence the findings. Therefore, successful testing can be performed only
with cooperation from the plant management. For example, if the plant lacks
scales, or bulk measuring devices, or good capacity materials handling devices
for evaluating raw-waste and residues, they must be brought to the plant and
used on a temporary basis during the testing period to ensure adequate data is
collected.
The EPA Testing Manual for Solid Waste Incinerators describes the types
of procedures, protocols and tests that should be followed in testing and
evaluating any incinerator — municipal, industrial, commercial or
institutional installation.
Preliminary Test Arrangements
f
Preliminary visits were made by the evaluation team to each incinerator
plant approximately six weeks before the testing period to ensure that all
necessary logistical arrangements were completed well before aptual testing
began. During these preliminary surveys the following information was
obtained.
1. Normal burning schedules, charging rates, weighing procedures,
cycles of operation, and related operational data.
2. Physical characteristics of the plant, such as solid waste
storage provisions, charging method, pollution abatement equipment
and residue handling equipment.
3. Sampling locations for solid waste, residue, and exhaust gases
as well as steam production.
-53-
-------
4. Location and size of stack sampling ports and the scaffolding
requirements for performing stack sampling. Stack modification was
not required for any of the sites tested.
5. Types, location, and form of readout of plant instrumentation.
Arrangements were made to have these instruments calibrated, if
necessary, before the study began and to install additional fuel
meters to record fuel usages. Each plant had kept records of these
instrument readings, and arrangements were made to obtain the
readings for the months preceding the study period.
6. Availability of electricity (type and location of outlets,
quantity of power, voltage, size of circuit breakers or fuses, etc.)
and water.
7. Location of economic data and names of personnel to contact
regarding this data.
8. Types and meanings of all alarm signals and appropriate action
to take should an alarm sound.
9. Types and composition of auxiliary fuel, and analytical data
regarding the fuel.
10. Names and telephone numbers of personnel connected with the
management and/or operation of the plant, such as Director of
Public Works, superintendent, foremen, etc.
11. Any available data from previous studies of the incinerator
such as burning rates, emission rates, and efficiency.
12. Determination of the total auxiliary fuel consumption,
firing rate, and burning time periods, including burn-down and
cooling period.
13. Drawings of the incinerator, design data, and both
theoretical and actual performance data.
The study team then notified the Office of Solid Waste Management
Programs in writing 30 days prior to the test that this data had been
assembled to allow an Office representative to be present as an observer at
each test. Mutually convenient test dates were established.
-54-
-------
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-------
TABLE 12
SUMMARY OF PARTICULATE EMISSION TEST RESULTS
PARTICIPATE EMISSIONS TEST ORLANDO, FLORIDA INCINERATOR
Test Run No. &
Charge Rate (Lbs/Hr)
Burn Rate (Lbs/Hr)
Testing Periods:
Start-up Time
First Charge
Start Test
TOTAL TEST TIME
DRY CATCH
Lbs/Hr
GN/ACF*
GN/SCFD/
GN/SCFD 12 C02
GN/SCFD 3.5 C02
GN/SCFD 50 Excess Air
Lbs/100 Lbs Charged
Lbs/100 Lbs Burned
Lbs/1000 Lbs Flue Gas
CONDENSER CATCH
Lbs/Hr
GN/ACF
GN/SCFD
GN/SCFD 12 C02
TOTAL
Lbs/Hr
GN/ACF
GN/SCFD
GN/SCFD 12 C02
1
5/19/75
2951
2168
8:00
8:39
9:42
4 hr.
39 min.
1.2407
.0125
.0308
.0629
.0183
.0465
.0417
.0633
.0559
.0634
.0006
.0016
.0032
1.3041
.0131
.0323
.0661
2
5/20/75
2860
2177
8:00
9:15
10:15
4 hr
0 min.
1.5700
.0144
.0392
.0800
.0233
.0599
.0545
.0774
.0720
.0962
.0009
.0024
.0049
1.6662
.0153
.0416
.0849
Date
3
5/21/75
2586
1933
7:15
7:48
8:45
4 hr
35 min.
1.8295
.0159
.0470
.0754
.0220
.0717
.0710
.1016
.0812
.0675
.0006
.0017
.0027
1.9174
.0169
.0488
.0781
4
5/22/75
3157
2290
7:00
8:05
8:30
4 hr.
0 min.
2.6236
.0219
.0669
.1190
.0347
.1072
.0943
.1309
.1167
.1349
.0011
.0034
.0061
2.7585
.0230
.0703
.1252
Avg. of 4
Test Runs
2889
2142
1.8160
.0162
.0460
.0843
.0770
.0713
.0654
.0933
.0815
.0905
.0008
.0023
.0042
1.9116
.0171
.0483
.0885
Grains/Actual Cubic Feet
Grains/Standard Cubic Feet, Dry
-88-
-------
TABLE 13
EXHAUST GAS CONDITIONS IN STACK
ORLANDO, FLORIDA INCINERATOR
Test Run No. & Date
Velocity, Ft/Min
Temperature, Deg F
Volume, Actual Cubic
Feet, Min.
Volume, Standard Cubic
Feet, Min. Dry
Moisture, By Volume
Condensate Method
Auxiliary Fuel Consumed
(ft3/min)
Average Velocity of Sampled
Gases at Nozzle Ft/Min.
% Isokinetic
1
5/19/75
1363.05
847
11600
4161
11.70
33.3
1334.4
97.9
2
5/20/75
1495.47
994
12726
4074
12.40
28.8
1391.4
93.1
3
5/21/75
1574.13
1019
13396
4126
14.34
20.5
1608.0
102.1
4
5/22/75
1643.48
1077
13986
4110
15.08
18.6
1637.4
99.6
Avg. of 4
Test Runs
1519.03
984.25
12927
4117.75
13.38
25.30
1492.8
98.2
TABLE 14
SUMMARY OF EXHAUST GAS ANALYSIS
ORLANDO, FLORIDA INCINERATOR
Test Run No. & Date
C02 (Total)
C02 in Fuel
Net C02 in Stack Gas
CO ppm
02%
N2%
Dry Molecular Weight
Mol. Wt. w/Moisture
1
5/19/75
6.70
.83
5.87
(not measured)
12.00
81.30
29.55
28.20
2
5/20/75
6.60
.75
5.88
(10.
12.10
81.30
29.54
28.11
3
5/21/75
8.00
.52
7.49
0.
11.90
80.10
29.76
28.07
4
5/22/75
7.20
.48
6.74
12.40
80.40
29.65
27.89
Avg. of 4
Test Runs
7.13
.645
6.50
0.
12.1
80.78
29.63
28.07
-89-
-------
Emission Test Results, Siloam Springs, Arkansas
During the period of October 1 through 4, 1975, the survey team conducted
three test runs on one of the incinerators and its matching steam boiler that
was installed in the Siloam Springs plant. Two tests were run on the boiler
stack and one on the heat dumping, or normal incinerator, exhaust.
The first two regular tests were conducted entirely on the gas emitted
by the boiler exhaust stack. Full steam production was called for during
these two runs and consequently 100 percent of the exhaust flow passed through
the boiler and out the boiler stack. Constant monitoring of the heat dumping
stack confirmed that all exhaust passed through the boiler.
The results of the two tests averaged 0.0302 grains per standard cubic foot
of dry exhaust gases corrected to 12% CO . Auxiliary fuel consumption during
each test was low enough that no correction for CO- produced by the fuel was
required.
The third test was conducted with steam production not in operation. All
gases from the incinerator were exhausted directly to the atmosphere, bypassing
the boiler entirely. The result of this test averaged 0.0367 grains per
standard cubic foot of dry exhaust corrected to 12% C0_. In this case also,
the fuel consumption was so low that no correction for CO produced by the fuel
was required.
Waste charging and composition rates were monitored and are reported in
Chapters 7 and 8. Visible emissions were noted infrequently and were usually
associated with an audible explosion (possibly aerosol cans) within the unit.
The exhaust temperature from the boiler stack was extremely low when compared
to the exhaust of the main, or dumping, stack. This would indicate excellent
heat absorption, and hence efficiency rate, in the boiler itself.
The data for each test is given in Tables 15, 16, 17 and 18.
-90-
-------
CO
£-H
J
JI3
CO
3 CO
«4j
EH CO
CO |Z
H -5
H W
W <
10 H
rH ^ M
ij CO
W P O
j C^ £5
PQ H M
yl-^
PM
0
>*-x
H-
Q
S
E
CJ
CO
^
S
CJ
^
rl
43
co
>/^
rH
CN
0
CJ
CM
i-H
(jy
*
e
CJ
CO
o
=«=
4J
CO
0)
H
tt)
4-1
cd
Q
co -* •* co
r-» 10 vo co
CM CM • CM CO
H
•si- vO IO O\
IO rH 00 rH
r~ vO VO IO
•sT vO IO CM
CM CO CO vO
c^ 10 r^» ^f
rH IO CO O
t** C3^ 00 O\
CO CO CO VO
CM iH vO IO
CTv vO CM *^
CM IO «* 0
rH H < CM H
C B 60
O 3 TH
•H TJ 43 0) f*,
4J 4-1 M
0 to >> 0 Q
3 0 rH 3
^rt ^ »\
o c e
rl -H tt) • 0
a, rt M A! -H
e 4-i o s
S X cd C
Cfl tt) (3 CU
M rt C tt)
43 "rl pt4
rH 00 00 Cd
rH 3 C B 0
3 0 -H -H
M^ J«J 4-) Q) -O
43 cd 43 3
CO 4-1 O 4-1 CJ
cd iH
00 *O O 13
•> C C W rl
^«! -H -H cd
CJ fi, Tj Tj
a} to •> (U ft
4-1 O ^ 4J Cd
CO CO O to 4-1
tt) CO 0) CO
rl 4J >
tt) S co -H -H-
rH 0 T)
•H t-l rl
O 4-1 Q) CO
43 rH 0)
CO -H • CO C
CU CO O CO Cd *H
43 6045 CU 60 S
^J O
^ >, tt) 3 rH ^.
B C 43 4-1 rH 4J
O Cd 4-1 Cd tt)
rl rl tt)
H_| »^ ^J (JJ »Q ptj
(U tt) rH C3
"O 4J rl -H Cd O
ai a tt) o TH
4J 0) 4J 45 C 45
4J > C ? 3
•H tt) OJ 0) O CJ
B to 43 'd
a) a 4-1 4J I-H
•rl 4J Cd
00 00 t*. 3 3
C C CO 45 43 4J
•H vH CO CO O
tt) > C <
45 rH CO O CO •
Cd Cd iH CO
CO > 60 4-1 S M
cd O3
5 O tt) Cd rl 4->
•H 43 rl tt) CO
CO S 4-1 4J rH to •
cfl cfl K -H 0) >>
60 C 4-1 0) O p. rl
!», o 43 B Q
rH TJ 4-> CU
rH 1 4-1 CO CU 4-1 •>
cd o cd a) 4: 4-1
to 0) 43 4-1 CO 0)
CO tt) 43 cd tt)
4-1 CO C 4-1 60 tn
CO |S TH CO
tt) 0) 0 tt) C 0
4J 43 rH >> *J iH iH
H 0 45
O CU C TJ 01 3
-C 43 tt> rl CO U
4J . 4J iH -H -H
4-1 O 43 rl 13
0) 0 CO -H 4J to
CO 0) 4J MH 0) Cd
0) <4H O MH tt) S T3
43 MH 55 tt) 43 tt) C
4J tt) 4J to CO
4-1 4J 4-1
60 C • 0 60 X CO
C iH M C
-------
TABLE 16
SUMMARY OF PARTICULATE EMISSION TEST RESULTS
PARTICIPATE EMISSIONS TEST SILOAM SPRINGS, ARKANSAS, INCINERATOR
Test Run No. & Date
Charge Rate (Lbs/Hr)
Burn Rate (Lbs/Hr)
Testing Periods:
Start-up Time
First Charge
Start Test
TOTAL TEST TIME
1
10/3/75
2478
1635
9:00
10:00
11:34
2 hr.
32 min.
2
10/3/75
2392
1673
9:00
10:00
14:47
2 hr.
30 min.
Avg. of 2
Test Runs
2435
1654
3
10/4/75
2680
1527
8:00
9:00
10:02
2 hr.
32 min.
DRY CATCH
Lbs/Hr
GN/ACF*
GN/SCFD/
GN/SCFD 12 C02
GN/SCFD 3.5 C02
GN/SCFD 50 Excess Air
Lbs/100 Lbs Charged
Lbs/100 Lbs Burned
Lbs/1000 Lbs Flue Gas
.2923
.0047
.0069
.0267
.0078
.0165
.0122
.0182
.0119
.5613
.0069
.0090
.0336
.0098
.0250
.0236
.0351
.0166
.4268
.0058
.0080
.0302
.0088
.0208
.0179
.0267
.0143
.4456
.0057
.0202
.0367
.0107
.0374
.0165
.0314
.0343
CONDENSER CATCH
Lbs/Hr
GN/ACF
GN/SCFD
GN/SCFD 12 C02
.4403
.0071
.0104
.0402
.5069
.0062
.0081
.0303
.4736
.0067
.0093
.0353
.1235
.0016
.0056
.0102
TOTAL
Lbs/Hr
GN/ACF
GN/SCFD
GN/SCFD 12 C02
.7326
.0119
.0173
.0668
1.0682
.0130
.0171
.0640
.9004
.0125
.0172
.0654
.5691
.0073
.0258
.0463
Grains/Actual Cubic Feet
Grains/Standard Cubic Feet, Dry
-92-
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TABLE 17
EXHAUST GAS CONDITIONS IN STACK
SILOAM SPRINGS, ARKANSAS, INCINERATOR
Velocity, Ft/Min
Temperature, Deg F
Volume, Actual Cubic
Feet, Min
Volume, Standard Cubic
Feet, Min. Dry
Moisture, By Volume
Condensate Method
Auxiliary Fuel Consumed
(ft3/min)
Average Velocity of Sampled
Gases at Nozzle Ft/Min
% Isokinetic
Test Run No.
1 2
10/3/75 10/3/75
1950,65 2591.11
273 254
7192 9553
4754 6616
7.78 5.92
1.066 0.0
1962.6 2400.
100.6 92.6
TABLE 18
& Date
3
10/4/75
2550.44 Two separate
1333 stacks tested.
Averaging not
9046 applicable.
2519
4.53
0.132
2565
102.
SUMMARY OF EXHAUST GAS ANALYSIS
SILOAM
CO- (Total)
CO- in Fuel
Net CO™ in Stack Gas
CO ppm
00%
N 7
Dry Molecular Weight
Mol. Wt. w/Moisture
SPRINGS, ARKANSAS INCINERATOR
Test Run No.
1 2
10/3/75 10/3/75
3.10 3.20
.02 .0
3.08 3.20
10. 10.
15.5 16.20
81.40 80.60
29.12 29.16
28.25 28.50
& Date
3
10/4/75
6.60 Two separate
.006 stacks tested
6.594 Averaging not
25. applicable.
13.50
79.90
29.60
29.07
-93-
-------
CHAPTER 11
LABORATORY ANALYSES OF RAW WASTES AND RESIDUES
Preparation of Laboratory Samples
Laboratory analysis of the waste "as received" and of the residue
remaining is used in evaluating the problems that may arise in incinerating a
particular waste stream, as well as evaluating a particular incinerator in
dealing with such waste. The make-up of the waste affects the quality of the
stack emissions, the quantity of auxiliary fuel that must be used, its worth
as a fuel for energy recovery, and the weights and volumes of residue generated.
The combustibles remaining in the residue indicate completeness of'combustion
and reduction.
The laboratory testing should determine the proximate analysis: the
moisture content, the combustible and non-combustible content and the heat
content of the waste and residue. It should also determine the ultimate
analysis (in terms of carbon, hydrogen, sulfur, chlorine, oxygen and nitrogen).
This requires laboratory samples that have been reconstituted accurately from
the bulk samples that were assembled to determine waste composition.
Incinerator and waste stream testers have been performing such laboratory
analyses for years, as an aid in designing incinerators, and for evaluating
the results of the combustion process. With the advent of waste-heat recovery
and steam production through incineration of solid wastes, there is an even
more pressing need for such analysis, and on an extremely accurate basis. If
the waste is to become a fuel (and a replacement for other energy sources, such
as fossil fuels) we must know a great deal about it if we are to evaluate its
ability to produce energy on an efficient basis.
When we examine residential, commercial and certain industrial waste, we
find that we are dealing with an extremely variable product. Despite the
analytical problems involved, it is essential that we develop reliable methods
for determining heat output of the particular waste being burned; in order to
calculate the amount of energy that can be captured in heat transfer methods
of varying designs and efficiencies.
-94-
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At first glance, we can see that waste is a relatively inefficient fuel
compared to fossil fuels. It takes far greater weights and volumes of waste to
produce the heat output found in a pound of coal, a gallon of oil, or a cubic
foot of gas. Unfortunately, the problem is more complicated than this.
Compared to the uniformity of weight to volume, and heat output to a unit of
weight or volume, found in fossil fuels, solid waste is a product that
continually varies. No two cubic yard lots of it are alike on an "as received"
basis. The density (weight per cubic foot) will vary from load to load; as
will the moisture content; the percentage of combustible material versus the
non-combustibles; and the heat content, or Btu value,for a given unit of weight
or volume.
With these conditions, the laboratory testing methods that have been used
to date to determine proximate analysis and ultimate analysis of solid waste
could probably be improved upon. They were originally adapted from methods
used for testing more uniform products than waste. When huge flows of several
tons per day of waste are reduced to a few pounds for testing purposes, the
chance for error is substantial when dealing with such a variable product. The
best we can hope for from the laboratory are good averages of the conditions
found in the waste stream over the test period.
The same procedure was followed at each of the three plants for preparing
laboratory samples of the "as received" waste. Four of the bulk samples that
had been assembled at each plant to determine the composition of the waste
on a percentage-by-weight basis, were selected for analysis. A 20 pound
laboratory sample was then prepared daily from each, reconstituted in the exact
percentages by weight found in the large sample.
Each component in the laboratory sample was kept separate in sealed
plastic bags. Sealing is important to ensure that complete moisture content is
retained. The combustibles were kept separate from the non-combustibles. All
components were clearly identified by tags, with the exact net weights of each.
Each entire 20 pound sample was double-bagged and sealed, and identified as to
date and source.
Representative one cubic foot laboratory samples of the residue were also
taken daily from each test incinerator. These were used to determine the
proximate analysis: moisture content, ash and volatile content, and heat content,
as well as tcr perform an ultimate analysis of the unburned combustibles and
fines. These samples were also sealed in plastic bags to prevent loss of
-95-
-------
moisture, then tagged and identified as to date and source.
Proximate Analysis
The moisture content of the incoming solid waste and residue samples from
each plant were determined by reconstituting the daily samples into one total
sample for each plant. Moisture of the total sample is assumed to be in the
combustible portion only. In each laboratory analysis the non-combustible
portion of the waste sample and of the residue sample was discarded after the
total moisture content had been determined. These materials (glass, metal,
rock, etc.) are assumed to be inert, and will not release any practical energy
upon heating.
The reconstituted combustible samples were prepared for further analysis
in a manner which insured they were sufficiently homogeneous in composition to
allow replicate one gram subsamples to be extracted that were representative of
the entire sample.
The heat content (Btu/lb) of the combustible portion on a dry basis was
then calculated for both waste and residue samples. From this was calculated
the heat content of the "as received" waste, which, due to moisture and non-
combustible portions, is always lower than the heat content of the combustible
proportion on a per pound basis.
Ultimate Analysis
Ultimate chemical analyses were performed on the composite subsample of
the raw waste and on the unburned combustibles in the residue to determine
the percentages (by weight) of carbon, hydrogen, sulfur, chlorine, oxygen
and nitrogen.
The ash contents of the prepared subsamples used for the ultimate
analysis were determined. The percentages by weight as determined on a dry
basis were adjusted to an "as received" basis by assuming that the samples
contained only the six listed chemical elements, plus moisture and inerts.
The percentages of the eight constituents were adjusted on a weight basis to
100 percent.
Tables 19 and 20 show the results of these laboratory investigations
on both the wastes and the residues at all three sites. Appendix D lists the
procedures and methods used.
-96-
-------
TABLE 19
SUMMARY OF WASTE ANALYSES
ANALYSES
COMPOSITION OF TOTAL SAMPLE
"AS RECEIVED":
Moisture %
Total Dry Matter %
Total Sample
Moisture %
Non-Combustible %
Combustible %
Total Sample
COMPOSITION OF DRY PORTION:
Non-Combustible %
Combustible %
Total
ANALYSIS OF COMBUSTIBLE PORTION:
Carbon %
Chloride (Total) %
Hydrogen %
Nitrogen %
Oxygen %
Sulfur %
Ash %
PAHOKEE
49.9
50.1
100.0
49.90
13.59
36.51
100.00
27.13
72.87
100.00
39.42
.12
5.92
1.14
39.72
.09
13.59
ORLANDO
33.96
66.04
100.00
33.96
10.72
55.32
100.00
16.23
83.77
100.00
39.90
.12
6.02
1.48
41.68
.08
10.72
SILOAM SPRINGS
20.8
79.2
100.0
20.80
29.28
49.92
100.00
36.97
63.03
100.00
47.3
0.759
7.12
0.528
35.54
0.10
5.51
HEAT CONTENT (Btu/Lb)
In Dried Combustible
Portion
In Total "As Received"
Waste
6596
2408
6973
3857
8720
4353
-97-
-------
TABLE 20
SUMMARY OF RESIDUE ANALYSES
ANALYSES
COMPOSITION OF TOTAL SAMPLE
"AS RECEIVED":
Moisture %
Total Dry Matter %
Total Sample
Moisture %
Non-Combustible %
Combustible %
Total Sample
COMPOSITION OF DRY PORTION:
Non-Combustible %
Combustible %
Total Sample
ANALYSIS OF COMBUSTIBLE PORTION:
Carbon %
Chloride (Total) %
Hydrogen %
Nitrogen %
Oxygen %
Sulphur %
Ash %
HEAT CONTENT (Btu/Lb) :
In Dried Combustible Portion
In Total "As Received" Residue
PAHOKEE
0.05
99.95
100.00
0.05
94.33
5.62
100.00
94.38
5.62
100.00
2.31
0.28
0.06
0.31
2.18
.53
94.33
301
16
ORLANDO
.05
99.95
100.00
0.05
94.51
5.44
100.00
94.56
5.44
100.00
2.40
0.31
0.06
0.13
2.18
.41
94.51
306
17
SILOAM SPRINGS
9.24
90.76
100.00
9.24
55.42
35.34
100.00
61.06
38.94
100.00
18.9
0.331
1.4
0.252
2.76
0.33
76.3
2370
838
-98-
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CHAPTER 12
INCINERATOR EFFICIENCY
Various calculations determine the efficiency of performance of
incinerator systems. The percent of weight reduction and the percent of
volume reduction in converting the waste to an ash residue are the most obvious
indicators. This involves measuring and weighing the "as received" waste and
the residue remaining, and comparing the two sets of data. In addition, there
is the percent of available heat released; and the combustible material
remaining in the residue that can be driven off by further heating. This
involves chemically analyzing the raw waste and the residue; and determining
the heat that can be driven off from each. From the viewpoint of efficiency
in minimizing impact on the air environment,emissions from the stack are the
determining factors.
Another factor determining the efficiency of controlled air incinerators
is the comparison of the auxiliary fuel consumption against the pounds of
waste burned in a given period.
Chapter 11 shows the efficiency of each of the tested incinerators from
the viewpoint of extraction of the heating value of the waste. In short, the
analysis of the residual values in the residue compared to the original waste
shows the thoroughness of the combustion process. Chapter 10 reveals the
treatment of the gases and the degree of emission of potentially harmful
substances into the air environment.
Tables 21, 22 and 23 show the weight and volume reductions rrom the
"as received" waste to the residue, on each of the test days at each plant,
as well as the overall average reductions for the entire test period at each.
They also relate the consumption of auxiliary fuel to each ton of waste
destroyed. From this aspect, the efficiencies of each incinerator were
remarkably close when the averages are examined.
-99-
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TABLE 21
WASTE REDUCTION - PAHOKEE
Average
WEIGHT REDUCTION
Sample
No.
1
2
3
4
Total
Weight
of Waste
(Lbs.)
9,780
15,130
9,830
12,040
Total
Weight of
Residue
(Lbs . )
2,670
4,235
3,020
4,440
Weight
Reduction
(%)
72
72
69
63
11,695
3,591
69
1
2
3
4
VOLUME REDUCTION - PAHOKEE
Sample
No.
Total
Weight
of Waste
(Lbs . )
Average
Density
(Lbs. /Ft.3)
Total
Volume
of Waste
(Cu. Ft.)
Total
Volume of
Residue
(Cu. Ft.)
Volume
Reduction
(%)
9,780
15,130
9,830
12,040
Average 11,695
10.5
9.7
13.0
11.4
11.2
933
1560
756
1056
1076
83
85
88
136
98
91
94
88
87_
90
1
2
3
4
Average
FUEL CONSUMPTION - PAHOKEE*
Test
Day
Total Weight
of Waste
(Ibs.)
Total 24 hr.
Oil Consumed
(gals.)
Oil Per Ton of
Waste Burned
(gals.)
9,780
15,130
9,830
12,040
11,695
88
127
89
111
104
18
17
18
18
18
*Fuel Cost per ton of waste burned during testing @ 0.43 gal. #2 oil = $7.74
-100-
-------
TABLE 22
WASTE REDUCTION - ORLANDO
1
2
3
4
Average
WEIGHT REDUCTION
Sample
No.
Total
Weight
of Waste
(Lbs.)
Total
Weight of
Residue
(Lbs.)
Weight
Reduction
(%)
24,500
27,360
22,940
25,040
24,960
6,980
7,320
6,120
9,160
7,395
71
73
73
63_
70
VOLUME REDUCTION - ORLANDO
Sample
No.
1
2
3
4
Average
Total
Weight
of Waste
(Lbs.)
24,500
27,360
22,940
25,040
24,960
Average
Density
(Lbs. /Ft.3)
19.1
11.7
8.4
10.8
12.5
Total
Volume
of Waste
(Cu. Ft.)
1283
2338
2731
2319
2168
Total
Volume of
Residue
(Cu. Ft.)
128
117
127
208
145
Volume
Reduction
(%)
90
95
95
91
92
FUEL CONSUMPTION - ORLANDO *
Test
Day
1
2
3
4
Total Weight
of Waste
(Ibs.)
24,500
27,360
22,940
25,040
Total 24 hr.
Gas Consumed
(Cu. Ft.)
22,100
15,400
13,000
11,200
Gas Per Ton of
Waste Burned
(Cu. Ft.)
1804
1126
1130
895
Average 24,960 15,425 1239
* Fuel cost per ton of waste burned during testing @ $1.30/mcf gas = $1.62
-101-
-------
TABLE 23
WASTE REDUCTION - SILOAM SPRINGS
WEIGHT REDUCTION
Sample
No.
1
2
3
Average
Total
Weight
of Waste
(Lbs.)
14,420
16,696
10,640
13,919
Total
Weight of
Residue
(Lbs.)
5,120
5,580
3,240
4,647
Weight
Reduction
(%)
65
67
70
67
VOLUME REDUCTION - SILOAM SPRINGS
1
2
3
Average
Test
Day
1
2
3
Total
Weight
of Waste
(Lbs . )
14,420
16,696
10,640
13,919
FUEL
Total
Average Volume
Density of Waste
(Lbs. /Ft.3) (Cu. Ft.)
8.7 1657
6.9 2420
7.6 1400
7.7 1826
Total
Volume of Volume
Residue Reduction
(Cu. Ft.) (Z)
104 94
123 95
71 95
99 95
CONSUMPTION - SILOAM SPRINGS *
Total Weight Total 24 hr.
of Waste Gas Consumed
(Ibs.) (Cu. Ft.)
14,420
16,696
10,640
3590
3610
2055
Gas Per Ton of
Waste Burned
(Cu. Ft.)
499
433
388
Average 13,919 3085 440
* Fuel Cost per ton of waste burned during testing @ $0.92 mcf gas = $0.40
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CHAPTER 13
ECONOMIC ANALYSIS
Capital Costs
Design and engineering costs for the modular small incinerator plants are
low. Mechanization is considerably reduced compared to large scale municipal
incinerator plants: overhead cranes, storage pits, residue quench tanks,
expensive pollution control devices (dry or wet), and high stacks are not
utilized. Hence, plant construction is considerably simplified and much less
expensive per ton of installed capacity compared to the large plants.
Incinerators of over 300 tons per day, installed between 1965 and 1967,
reflected capital investments ranging from $5,000 to $8,500 per ton. In 1973,
a 300 ton per day plant had a capital cost of $11,000 per design ton . The
modular incinerator plants in the present study ranged from $9,093 per ton of
design capacity at Orlando to $9,495 at Pahokee, to $17,667 with steam
production capability at Siloam Springs.
A direct comparison proved difficult between the small and large municipal
plants for the cost of steam production equipment. The few large plants
attempting energy recovery to date have installed more complicated systems. In
sheer dollars, where the modular plants show a capital investment of under
$110,000 for steam recovery boilers, the large plants have spent many times
this figure. In 1973 it averaged $16,000 per design ton.
Table 24 shows the breakdown of capital investment at the test sites for
the incinerator equipment, all structures, and their service utilities to bring
the plant "on line". In Pahokee and Orlando, the land was owned by the
municipality several years before the incinerator plant was located on it.
The town of Siloam Springs pays Allen Canning Company $1.00 per year on a
twenty year land lease for the incinerator site located adjacent to the canning
plant. Under these circumstances it proved difficult to assign a true value to
the land in factoring capital costs.
Orlando and Siloam Springs placed a series of contracts for their plant
construction, each separating out major items so that costs could be readily
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identified. Pahokee combined plant, sewer installation, landscaping and
driveways into one contract. The cost breakdown of major components is
unknown.
The life of the small modular plants is still unknown exactly. However,
experience with the type of buildings used would indicate that 20 years is
reasonable. The incinerators and steam boiler equipment are estimated to have
a useful life of 15 years, though this is yet to be proven. These life cycles
have been used in arriving at depreciation figures for calculating total
operating costs.
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TABLE 24
BREAKDOWN OF 1974 CAPITAL INVESTMENTS
PLANT
PURCHASE
PRICE*
ESTIMATED
LIFE
(YEARS)
ANNUAL
DEPRECIATION
COST
% OF
PURCHASE
PRICE
Pahokee
Plant Bldg. & Fencing
with Utilities
Incinerators (2)
$ 57,825 20
103,576 15
TOTAL $161,401
Design Capacity - 17 tons/10 hr. day
Cost per ton of Design Capacity $ 9,494
Orlando
Plant Bldg. with Utilities
Scale House & Office
Incinerators (8)
Fence & Sign
$263,077
31,521
600,000
14,798
20
20
15
20
2,891
6,905
9,796
13,154
1,576
40,000
740
36
64
100
29
3
66
2
TOTAL $909,396
Design Capacity - 100 tons/10 hr. day
Cost per ton of Design Capacity $ 9,093
Siloam Springs
54,730
100
Plant Bldg., Road & Fence
with Utilities
Incinerators (2)
Energy Recovery Units (2)
$118,000
146,000
107,000
TOTAL $371,000
Design Capacity - 21 tons/10 hr. day
Cost per ton of Design Capacity $ 17,667
20
15
5,900
16,867
22,767
32
68
100
* The above capital costs represent all labor, materials and installation
charges for complete finished construction, as well as the installation of all
necessary service utilities. Depreciation is on a straight line basis.
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Vehicle Costs
Vehicle requirements are minimal. The most satisfactory plant vehicle is
a front-loading tractor with an estimated life of five years. The average cost
is $6,000.
TABLE 25
1974 PLANT VEHICLE PURCHASE COSTS
PURCHASE
PRICE
ESTIMATED
LIFE
(YEARS)
ANNUAL
DEPRECIATION
COST *
Pahokee
1 Front Loading Tractor
$ 5,835
1,167
Orlando
3 Front Loading Tractors
1 Dump Truck, Used
1 Pickup Truck
Siloam Springs
1 Front Loading Tractor
$18,000
4,000
3,540
$25,540
$ 6,025
5
5
5
5
3,600
800
708
5,108
1,205
Depreciation is straight line.
Operating Costs
The major operating costs with municipal small incinerators are for labor
and auxiliary fuel. The relationship between these two figures varies
considerably depending on local cost structures.
Plants using natural gas at present have lower auxiliary fuel costs than
those using No. 2 diesel fuel. Pahokee and Orlando are good examples of this
differential in the State of Florida. In late 1975, No. 2 diesel oil was
selling to Pahokee for a price of 43(? per gallon, an increase of almost 100
percent in two years. Such oil has a heating value of 138,500 Btu per gallon.
Natural gas, on the other hand, was selling to Orlando for $0.13 per therm
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(100 cubic feet) which gives a heat production of 97,000 to 103,000 Btu. To
convert the purchase prices of the two fuels into a common denominator of Btu
output, No. 2 diesel oil currently costs approximately 2.3 times the cost of
natural gas, for Btu equivalent output, in the State of Florida. Unfortunately,
Pahokee has no access to natural gas and must use oil as its auxiliary fuel.
By October 1975, when the Siloam Springs plant was tested, using natural
gas, it was noted that the price per therm had almost doubled in less than a
year. It had risen from $0.058 in 1974 to $0.092 in mid 1975 per therm, or
100 cubic feet; still less expensive than central Florida.
Comparing total fuel bills for each plant against the actual tons of
waste burned during the past year, we find considerable differences between
the three plants in cost of fuel per throughput ton: Pahokee - $8.17;
Orlando - $1.24; and Siloam Springs - $0.82.
Labor costs varied considerably between the tested plants, due to base
rates and fringe benefits. Also, the staffing patterns differ considerably
as can be seen in Table 26.
All of the plants are too new to determine what the actual maintenance
costs will be over their life span. Each starts out using a budget figure
based on the recommendations of the manufacturers of the incinerators, the
buildings and the waste loading vehicles for both preventive and curative
maintenance actions. The major item of maintenance in all the plants appears
to be the refactory linings of the incinerators that can be damaged through
thermal shock and during ash removal. The tubes in the steam boilers may
prove an important maintenance item at Siloam Springs.
In an effort to establish accurately projected maintenance costs, the
study team made a survey of nine other similar municipal small incinerator
plants that had been in constant operation for at least two years. One had
been operating five and one-half years with no major replacement of refractory
linings and only some minor electric work performed. Three plants had been
operating for over three years. One reported it had performed a major repair
procedure on the refractory. The other two reported minor thermocouple
replacements. The five remaining plants that had been operating up to three
years reported, as did all plants, some patching of refractory linings and
some minor mechanical and electrical repair. One point made very clear was
that reftactory repair can be performed in-house, simply and quickly, and at
far lower cost than by hiring outside contractors. Further, all plants appear
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to feel that the manufacturers should provide annual preventive maintenance
contracts, as is done with many items of capital equipment.
Using the actual figures from these plants, combined with the first
year's experience with the plants under warranty, a projection of these costs
indicates that $0.37 per ton of installed capacity for the life of the
equipment is a reasonable maintenance figure for the plants with straight
incineration. With steam recovery, the figure would appear to be $0.48 per
ton of installed capacity. These figures have been used in Table 26. Table
27 shows a slightly higher figure as design capacity and throughput differ.
The Environmental Protection Agency feels that a more realistic
maintenance cost may be as high as 5% annually of the original purchase cost.
This is based on previous EPA experience with large scale solid waste
processing equipment. If this higher annual maintenance cost factor is
applied to the figures given in Tables 26 and 27, the annual operating costs
would increase per ton by $1.66 at Pahokee, $1.34 at Orlando and $2.93 at
Siloam Springs.
The cost of utilities (water, electricity and telephone) appears to vary
considerably between the plants - from $130 to $1,000 per month. The
electricity used at each plant in KW hours average per month was: Pahokee -
6,213 KW hours; Orlando - 27,100 KW hours; and Siloam Springs - 10,195 KW hours.
Water cost in a straight incinerator plant is low; used for plant clean-
up mainly. Pahokee uses a well and does not record or pay for water. Orlando
has a representative figure of $90.90 per month. Where steam is produced,
and with no condensate return, water and electricity run higher in cost than
fuel. This is seen at Siloam Springs, with annual costs of $1,890.00 for
water and $4,160.00 for electricity, or $6,050.00'total for the two utilities.
Fuel costs for the front loading vehicles are fairly consistent between
the plants and directly related to the equipment used. Supply costs (for
chemicals, paints, tools, uniforms, office supplies, vehicle tires and
batteries, housekeeping supplies, etc.) are hard to predict exactly over the
future years, as new plants are always faced with some abnormal expenditures
the first year.
Table 26 summarizes and compares the operating costs for all three plants.
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TABLE 26
ANNUAL 1975 OPERATING COSTS
1 . LABOR
Plant Supervisor
Plant Foreman
Plant Labor
Secretarial & Office,
assigned
Overtime Pay Total
Labor Overhead & Fringes
TOTAL DIRECT LABOR & FRINGES
2. AUXILIARY INCINERATOR FUEL*
3. U7 L.ITIES (Water, Electricity,
Telephone)
4. SUPPLIES & SERVICES**
5. MAINTENANCE FUND +
6. VEHICLE FUEL
TOTAL EXPENSES
TOTAL OPERATING COSTS t
Pahokee
$ 9,235
6,136 (1)
4,946
672
1,202
$22,191
$31,605
$ 2,561
$ 1,833
$ 1,635
$ 825
$38,459
$60,650
Orlando
$ 16,008
9,876
45,276 (6)
9,040
12,284
14,105
$106,588
$ 33,317
$ 10,272
$ 5,640
$ 9,620
$ 2,340
$ 61,189
$167,777
Siloam
Springs
$12,585
11,178 (2)
2,098
2,334
$28,195
$ 4,366
$ 6,350
$ 3,482
$ 3,125
$ 672
$17,995
$46,190
*
Low fuel costs at Siloam Springs are the result of a newly developed air-
fuel control system and lower gas prices than paid by Orlando; both sites
show the savings in natural gas prices versus #2 oil as used by Pahokee in
1975.
Plant, office and vehicle supplies.
Maintenance fund is based on $0.37 per design ton charged per year for
Pahokee and Orlando and $0.48 at Siloam Springs to plant equipment and
incinerator repair.
All figures were obtained from the books of account of each municipality.
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Comparative Total Costs
When the operating costs and the capital and financing costs are combined
into the total annual costs for each plant, complete comparisons can be made
between them. These stand out clearly when all items are reduced to the basis
of cost per ton processed annually as set forth in Table 27.
Unless a plant approaches its design capacity in the tonnage of waste it
processes annually, certain fixed overhead and operating costs cannot be
reduced below minimum levels. This is best illustrated at Pahokee with higher
unit labor and plant operating costs, as well as higher unit capital costs in
comparison with Orlando.
The study team desired to put all three plants on an equal basis for
comparison and included interest charges at both Pahokee and Orlando equivalent
to the rate being paid by Siloam Springs. As footnoted, neither Pahokee nor
Orlando are paying such charges and the true total costs per ton are $18.53 at
Pahokee and $8.50 at Orlando.
Steam generating equipment has been expensive in these first plants, as
seen from the Siloam Springs unit capital figures, which are more than double
those of Orlando. This high capital cost so heavily affects the Siloam Springs
unit cost structure that the total gross costs (before steam sales revenues
enter the picture) are 61% higher than that of Orlando.
A review of the Siloam Springs "Steam Sale Agreement" (Appendix E)
indicates that this situation should change by late 1976. When the figures
were assembled late in 1975, steam purchases were beginning to rise. The
purchase curve indicates that for the following year, the cannery will purchase
approximately 31 million pounds of steam, requiring 434,000 therms of gas at
a minimum price of $0.092. This would increase steam sales revenue, reducing
operating costs to under $1.20 a ton and reducing total costs to under $8.50
per ton, or fairly close to the total costs at Orlando. Each rise in fuel
costs that must be paid by the steam purchaser will reduce total costs further.
The prediction is that steam sales will completely offset direct operating
costs within two years, based on the curve of rising gas prices.
The serious effect of fuel costs can be seen at Pahokee, with No. 2 oil
boosting the fuel unit cost per ton processed to almost seven times that of
Orlando and almost ten times that of Siloam Springs, both of which use gas.
Admittedly, under-utilization and less sophisticated controls at Pahokee
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contribute to this. The difference a control system can make on fuel costs
can be seen in comparing Siloam Springs and Orlando.
Detailed examination of the books and records of each plant revealed
considerable differences in accounting methods, in the establishment of cost
centers and cost accounting, in general. As stated earlier in this report,
it is essential to weigh all incoming waste and possibly outgoing residue to
keep track of the efficiency of the operation and as a major basis for cost
control. As fuel, electricity and water usage affect operating costs, as well
as knowledge of whether the efficiency level cf the incinerators is being
maintained, it is imperative to have accurate flow meters installed and to
read them constantly.
When steam sales are being made, accurate pressure and recording/totalizing
flow meters should be installed at the steam outlet, adjacent to the boilers,
to prove, conclusively, the pressure and poundage of steam being delivered to
customers. Such meters must be maintained regularly to ensure accurate records.
Virtually every operation and record ties into throughput tons of waste
on a daily, weekly and monthly basis, and cost control should be set upon this
basis. Fluctuations in cost will often reveal the need for preventive or
corrective maintenance or variations in labor output. Cost accounting should
always set up maintenance labor, supplies and services in a separate center to
ensure that all costs are being properly charged to this function rather than
included with other operating accounts.
Finally, monthly summary reports to management, by cost center, prove
helpful if corrective action is required.
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-------
CHAPTER 14
STEAM PRODUCTION FROM SMALL INCINERATORS
The investigation of resource recovery has followed many paths in recent
years. Several major experiments deal with the removal and sale of metals,
paper products and glass from the waste stream. With the continued shortfall
of fossil fuels and steadily rising prices, considerable attention has been
placed on municipal waste as a source of energy and a substitute for coal, oil
or gas. The conversion of solid waste into combustible oil or gas by pyrolysis
is being studied for economic feasibility. In direct energy production from
incineration, at least three steam producing designs have emerged. Milled
combustibles in the solid waste stream have been used to augment the fuel in
conventional coal-fired boilers, used to produce steam for turbine generation
of electricity. Waterwall incineration has been installed in a few large
plants, producing steam from the waste heat in the primary chamber for the
generation of electricity. Controlled air incinerators utilize afterburner
gases.
Most proposals and ongoing experiments seem to envision mass production.
Waste from large cities and their surrounding suburbs is to be transported
into a processing plant of 300 to over 1,000 tons a day capacity, to take
advantage of economics of scale. This mass production approach seems to ignore
some important points.
The United States has 15 times as many towns of 8,000 to 200,000
population, generating small to medium tonnages of municipal waste, as it has
large cities of over 200,000. The most expensive aspects of waste management
in 1975 are collection and transportation costs, and the wider the area covered
the higher the costs. Industry is dispersed to a tremendous extent through the
smaller cities. When we examine resource recovery in the form of steam
production from waste, we see that much of this industry needs energy to
survive, but in relatively small unit quantities. In short, if we look at
municipal waste management as a completely engineered regional economic system,
there remains the question of the practical economies of size.
Based on the experiemts that have been conducted for producing steam from
municipal waste, it would appear that the mass production plants, as currently
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designed, do not have practical cost advantages. With mechanized facilities,
automated handling equipment and air pollution control devices installed, their
cost per ton of designed capacity is as high or higher than the small
incinerator modular plants. Even though they do not use auxiliary fuel, they
do not appear to be able to process waste on a total cost per ton basis any
cheaper than the efficient modular plants. When total ownership cost per ton
processed is added, they are often more expensive than the modular small
incinerator plants.
The raw fuel material, solid waste, can be delivered to the small plants
relatively inexpensively. The smaller plant can be constructed near sources
generating medium quantities of waste and still operate fairly economically,
whereas, the mass production plant must pay hauling and transfer costs as high
as $10.00 per ton in 1975 to obtain needed quantities to match its capacity.
Chapter 4 discussed the technical and corrosion problems of steam
production from waste in utility company boilers or in conventional "water-
wall" incinerators. From this point alone, unless the mass production units
considerably improve their engineering basis, and at an installed cost per ton
of capacity equal or lower than that of the modular units, the small controlled
air incinerators, producing less contaminated gases, appear to have an
advantage.
The mass production plants lack the flexibility and simplicity of design
that might be needed for expansion compared to the modular plants. They also
are faced with much more rigid site selection criteria because of their size,
complexity, and heavy vehicle traffic.
To date, the mass production plants have turned out a more flexible end
product. The steam they produce is normally planned as a first step - the
final product is electric power. Electricity can be delivered in wires over
a wide area inexpensively, while the modular plant, with its limited capacity
practically must produce steam to be used as steam; delivered in pipes to
customers relatively close to the plant.
The potential for modular small incinerator plants producing steam for
local industrial or institutional needs appears to have become a reality
during the past year. If the developments continue at the present rate, this
method offers an impressive energy alternative for hundreds of communities and
their steam-using industries. It also offers the possibility for a larger
city to be divided into incinerator plant zones, compact in size to reduce
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hauling costs, supplying steam to local industry or institutions.
The Impact on the U. S. Energy Needs
Based on the present efficiency of the controlled-air incinerator gas
boilers, and the known averages of heat production from municipal waste,
certain parameters and constraints apply when considering the use of this
method for producing steam.
Municipal waste is not as efficient a fuel as any of the fossil fuels.
It has a lower Btu output per pound in its average "as received" condition:
greater weights must be burned to produce the energy equivalent of coal, oil
or gas. The heat output of municipal waste "as received" averages 5,000 Btu/
Ib. This is one-half to one-third that of coal which ranges from 10,550 to
14,000 Btu/lb. A pound of #2 oil releases four times the energy of the
equivalent weight of municipal waste. It has not the compactness of fossil
fuel and far greater volumes must be burned to reach equivalent energy output.
Oil measures 31 to 35 cubic feet per ton; coal measures 45 to 50 cubic feet
per ton. Municipal waste usually ranges in density, in its "as received"
condition, from 130 to 400 cubic feet per ton. However, it also contains by
weight up to 30% moisture and up to 30% non-combustibles, neither of which
contributes to the release of energy. The combustible portion has densities
as low as 650 cubic feet per ton.
Designers of waste-heat recovery systems have accepted these ratios. The
materials handling equipment and the engineering of combustion systems
provide for the lower densities and larger volumes of fuel (solid waste) that
must be charged to produce satisfactory energy recovery.
When we consider controlled air incinerators, the contribution of
auxiliary fuel to the production of steam must be considerably less than the
fuel used in a direct-fired boiler. The burning waste must supply the bulk
of the energy, so that there are important net savings in fossil fuels.
Further, the gas emissions reaching the boiler tubes must be as uncontaminated
as possible to reduce corrosive effects and coating of the tubes. Emission
levels from the stack must remain within acceptable limits.
It requires, theoretically, 1,000,000 Btu from the fuel being burned to
produce 1,000 pounds of steam. Most boilers are only 70 to 75 percent
efficient in transforming this heat and 1,400,000 Btu must be produced by the
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fuel to obtain 1,000 pounds of steam. Natural gas has a theoretical heating
value of 100,000 Btu per 100 cubic feet. Ratings can be as low as 97,000
Btu. No. 2 diesel oil will average 138,500 Btu per gallon.
Hence, the fuel required in the average 70% efficient boiler to produce
1,000 pounds of steam would be approximately 1440 cubic feet of natural gas,
or 10 gallons of No. 2 diesel oil; or from 250 to 500 pounds of waste.
There are 2500 communities in the United States with populations between
8,000 and 100,000 that have industrial plants requiring steam. There are
another 85 communities between 100,000 and 200,000, and a further 160
communities over 200,000 in size, all of which have industry requiring steam.
It is estimated that these urban areas have a daily total waste
generation, six days a week, of 425,000 tons. If this averaged 5,000 Btu/lb,
the total energy contained would be four trillion, 250 billion Btu; which could
produce 2.975 billion pounds of steam at average efficiency.
If all this waste was burned to produce this amount of steam in the
controlled air design incinerators of the efficiency studied at Siloam Springs,
in place of natural gas or oil, the net savings in these fossil fuels, after
deducting the auxiliary fuel requirements, are in the order of 4.115 billion
cubic feet of gas per day. The savings in No. 2 diesel oil would be 29.1
million gallons daily.
Despite these impressive figures, both the modular small incinerator plant
producing steam as the end product, and the large incinerator-boiler producing
steam for generating electricity, are merely auxiliaries. They will never
process enough waste to meet the nation's requirements for industrial steam or
electricity. However, they can contribute greatly to our shortfall situation.
Further, they may lead to the most feasible method for processing a large
proportion of the nation's solid waste stream.
In the final analysis they must produce steam that is satisfactory to
many diverse customers and it must be sold on an equitable basis. Some
experimental plants give indications that such marketing can be achieved now,
if the,proper combination of designer, builder, municipality, financial
packaging and energy buyer are assembled.
-116-
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CHAPTER 15
SILOAM SPRINGS STEAM PRODUCTION
The Siloam Springs, Arkansas plant was selected as an example of the
engineering state of the art in 1975 for waste-heat recovery and steam
production. Five days of testing showed that the system and plant operated
effectively for the purpose intended, while accepting average municipal waste
without any prior treatment.
Tables 15 through 18 show that stack emissions were acceptable and, in
fact, considerably below the levels of the two other tested plants which did
not have the waste heat recovery feature.
The life of the boiler tubes and the effect of corrosive or coating
chemicals in the waste gases cannot be proven definitely, as the plant has been
operating for less than a year. However, based on visual inspection of the
tubes, the automatic tube cleaning system appears to be working efficiently.
An important determination during testing concerned the efficiency of
steam production in pounds per hour at 100 psig, compared to the Btu value of
the charged waste, combined with the use of auxiliary fuel. Waste was charged
during the test period for up to seven hours a day, while auxiliary fuel was
used over a period of 10.5 hours, including the warm-up and burn down periods.
Table 28 shows the steam produced per hour during waste charging, as well
as the total steam produced during a typical 10.5 hour day with auxiliary fuel
being burned. It shows the pounds of waste burned for the total period and
the auxiliary fuel used during three operating modes and in total. Table 29
analyzes and compares this data to show the pounds of steam produced for each
pound of waste burned, along with the amount of auxiliary fuel consumed Eor
each pound of steam produced. It then compares this method of producing steam
with the use of a direct fired boiler, operating at 70% efficiency, to show the
amount of fossil fuel that is saved by using the solid waste as the principal
source of energy for the steam production.
-117-
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TABLE 28
STEAM PRODUCTION AND FUEL CONSUMPTION SILOAM SPRINGS
Operating
Period
Warm-up (1/3 hr.)
Charging (7 hrs.)
Burn-down (3 hrs.)
Steam Waste
Produced Burned
none
4,795 Ibs./hr.
4,620 Ibs./hr.
Auxiliary
Fuel
Consumption
(Cu. Ft. Gas)
880
1560
1170
Total (10 1/2 hrs.
Period)
47,425
16,696
3610
Average Steam Pressure at Boiler....100 psig.
TABLE 29
TOTAL STEAM PRODUCTION FUEL SAVINGS ANALYSIS
Steam Produced (pounds) per boiler per day 47,425
Pounds of Steam Produced per Pound of Waste Burned 2.84
Cubic Feet of Auxiliary fuel Consumed per Pound of Steam Produced 0.076
Cubic Feet of Gas Saved per Pound of Steam Produced, Compared to a
Direct Fired Boiler Operating at 70% Efficiency 1.43
3
Value of Si loam Springs natural gas 970- Btu/f t
-118-
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There would be a further savings in fuel, not revealed by these figures,
if the system utilized a condensate return, as would normally be found in
closed boiler systems. All feed water at Siloam Springs is fresh and energy
is required to raise it from the incoming temperature of around 50 F to the
temperature of 338°F at which the steam is produced. Despite this, at a
production of 47,425 pounds of steam, the savings of natural gas over a direct
fired boiler were 66,774 cubic feet. At the current Siloam Springs price of
$0.092 per 100 cubic feet (one therm), this amounts to $61.43 savings per day
over the purchase of fuel to produce this amount of steam in a direct-fired
boiler.
The next point investigated was the operating efficiency of the waste
heat boiler, based on the total Btu input from both the solid waste and the
auxiliary fuel, compared to the total steam produced. The Btu value of the
charged waste is extremely important in such an analysis. Unfortunately,
without extremely sophisticated test equipment it is impossible to determine
this value on a charge by charge basis. The laboratory analysis of the
average waste was used. As seen from Table 19, the net average value on an
"as received" basis, amounted to 4,353 Btu/pound.
Calculating the efficiency of a direct-fired boiler, using a fuel with a
constant Btu output, is obviously simpler than calculating the efficiency of
waste-heat boilers. The heat transfer comes from burning a product that
continually varies in Btu value. In the type of controlled air incinerator
tested at Siloam Springs, the use of auxiliary fuel and air is designed to
compensate for these variations and control the temperature level in the gas
passing around the boiler tubes.
From a practical viewpoint, efficiency calculations can only use averages
in dealing with such waste-heat boilers. The assumption is made that the
waste does average out at a given Btu/pound figure.
Table 30 shows how boiler efficiency at Siloam Springs can be estimated
under one method. The total potential Btu output of the waste, coupled with
the output of the auxiliary fuel, is calculated. The total steam production
is measured and the theoretical energy that would be required to achieve this
production is then calculated. The two figures are compared to determine the
boiler efficiency.
-119-
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TABLE 30
BOILER EFFICIENCY ANALYSIS - SILOAM SPRINGS
Waste Burned 16,696 pounds
Heat Potential @4353 Btu/pound "as received" 72.7 million Btu
Auxiliary Gas Consumed 3,610 cu. ft.
Heat Potential @ 970 Btu/cu. ft 3.5 million Btu
Total Heating Potential 76.2 million Btu
Feedwater Inlet Temperature - 50°F
100 psig Steam Temperature - 338°F
Energy to raise 50°F to 338°F - 291 Btu/lb.
Energy to produce steam @ 338°F - 881 Btu/lb.
Total Energy Requirement 1,172 Btu/lb.
Energy requirement for 47,425 pounds of steam 55.5 million Btu ss
Theoretical Boiler Efficiency 72.8%
-120-
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Only considerable additional field testing of these systems will
definitely establish the total amount of steam they are capable of producing
from wastes of varying heat values, and hence the amount of direct-fired
boiler fossil fuels that they will save. With condensate return systems
incorporated, along with satisfactory automatic ash removal systems, the rate
of efficiency would climb further.
The pounds per hour of steam produced will vary with the design and
efficiency of the incinerator waste-heat boiler system. It will also vary
with the average Btu values of the waste as charged and the weight charged per
hour. Figure 19 illustrates these heat value-charging weight relationships.
10,000
9,000
8,000
CO
CD
7,000
Q
O
DC
0.
< 6,000
UJ
5,000
NET HEAT CONTENT
OF WASTE
800 1000 1200 1400 1600 1800 2000 2200
CHARGE RATE, LBS/HR. Figure 19
STEAM PRODUCTION BASED ON WASTE HEAT OUTPUT AND CHARGING
RATES.
-121-
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FOOTNOTE REFERENCES
1. Federal Register, December 23, 1971.
2. Present Status of Municipal Refuse Incinerators, American Society
of Mechanical Engineers, January 1975.
3. Achinger, W. C. and Daniels, L. E., An Evaluation of Seven Incinerators,
1970 National Incinerator Conference.
4. Achinger, W. C. and Daniels, L. E., An Evaluation of Seven Incinerators,
1970 National Incinerator Conference.
5. EPA, Office of Solid Waste Management, Municipal-Scale Thermal
Processing of Solid Waste, EPA Contract 68-03-0293, Recon Systems,
Inc., December 1975.
-122-
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APPENDIX A
FIELD TEST REPORTS
-123-
-------
Form #1
INCOMING SOLID WASTE
WEIGHTS
PLANT
PAGE
OF
ORGANIZATION
RECORDED BY
Truck
No.
1
2
3
4
5
6
7
8
9
10
Total
AVERAGE
Date
Gross Weight of
Truck and Waste
db)
Truck Tare
Weight
db)
Net Weight
of Waste
db)
Hour of Day
Delivered
Comments:
-124-
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Form #2
INCOMING SOLID WASTE BULK DENSITY DETERMINATION
PLANT
PAGE.
OF.
ORGANIZATION
RECORDED BY
Con-
tainer
No.
1
2
3
4
5
6
7
8
9
10
Average
Date
Dimensions
of
Container
(inches)
H x L x W
Cubic
Feet
of
Waste
Gross
Weight
of
Container
& Waste
(lb)
Con-
tainer
Tare Wt.
(lb)
Net
Weight
of
Waste
(lb)
Bulk
Density
of Waste
(Ib/cu-ft)
Comments:
-125-
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FORM NO. 3
PAGE OF
PLANT
CHARGING RATE & OPERATING DATA
DATE
ORGANIZATION
RECORDED BY
TOTAL WEIGHT CHARGED (LBS)_
TOTAL CHARGING TIME(HRS)
NO. OF CHARGES
TOTAL COMPLETE BURN TIME(HRS)
TIME OF
CHARGE
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
FINISH
START
TOTAL
FUEL CONSUMPTION GAS Q
METER READINGS OIL Q
LOWER
UPPER
TOTAL
INCINERATOR INTERIOR
TEMP. DEGREES F.
LOWER
UPPER
POWER ANAL
Meter R
Meter R
Power C
WATER ANAL
BOILER
PRESSURE
STEAM
LBS/HOUR
YSIS:
eading end of Day KWH
eading Begli
onsumed/Per
YSIS:
ining KWH
Lod KWH
-£ r» •'ran
Meter Reading Beginning
Water Consumed/Period
_GPH
GPH
-126-
-------
Form #4
INCOMING SOLID WASTE COMPOSITION DATA
FIELD SAMPLE
PLANT.
SAMPLE NO.
DATE
TIME
ORGANIZATION.
ANALYZED BY
Category or Component
COMBUSTIBLES
Food Waste
Garden Waste
Paper Products
Plastics, Rubber
leather
Textiles
Wood
Fines
NONCOMBUSTIBLES
Metals
Glass, Ceramics
Ash, Dirt, Rocks
TOTAL
Gross Weight
of Container
& Waste *
{.Ib & oz)
Container
Tare
Weight
(Ib & oz)
As Received
Weight
Net
(Ib & oz)
As
Received
Percentage
100.0
*Triple wrapped plastic bags
COMMENTS:
-127-
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Form #5
INCOMING SOLID WASTE COMPOSITION DATA
LABORATORY SAMPLE
PLANT
SAMPLE NO.
DATE
TIME
ORGANIZATION
ANALYZED BY
Category or
Component
COMBUSTIBLES
Food Waste
Garden Waste
Paper Products
Plastics, rubber
leather
Textiles
Wood
Smalls
Fines
NON COMBUSTIBLES
Metals
Glass, ceramics
Ash, dirt, rocks
TOTAL SAMPLE
As Received Weight (Ib & oz)
Gross
Wgt.
Container
Tare Wgt.
Net
Wgt.
20 Ib-Ooz.
As Received
Percentage of
Net
100.0
COMMENTS:
-128-
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Form #6
RESIDUE BULK SAMPLE DETERMINATION
FIELD DATA AND CALCULATIONS
PLANT
ORGANIZATION
RECORDED BY
Sample
No.
1
2
3
4
5
Average
Date
Dimensions
of
Container
(inches)
H x L x W
Cubic
Feet
of
Residue
Gross
Weight
of
Container
& Residue
(lb)
Container
Tare
Weight
(lb)
Net
Weight
of
Residue
(lb)
Bulk
Density
(Ib/cu-ft)
Comments;
-129-
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Form #7
RESIDUE DETERMINATION
LABORATORY SAMPLE
PLANT
ORGANIZATION
RECORDED BY ..
Sample
No.
1
2
3
4
5
TOTAL
Date
Dimensions
of
Container
(indies)
H x L x W
Cubic
Feet
of
Container
Gross
Weight
of
Container
& Residue
(lb)
Container
Tare
Weight
(lb)
Net
Weight
of
Residue
(lb)
Comments:
-130-
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Form #8
WASTE/TO RESIDUE REDUCTIONS
>LANT
5RGANIZATION.
CALCULATIONS
WEIGHT REDUCTION
Sample
No.
1
2
3
4
5
Total
Average
Date
Total
Raw
Weight
of Waste
Total
Weight
of
Residue
Difference
Residue
% _
Raw
Waste
% of
Reduction
of Raw
Weight
VOLUME REDUCTION
Sample
No.
1
2
3
4
5
Total
Average
Date
Raw
Weight
Waste
Avg.
Lbs/
Cu.ft.
Waste
Total
Cu.ft.
Waste
Cu.ft.
of
Total
Residue
Dif-
ference
Residue
%
Raw
Cube
% of
Reduction
of Raw
Cube
-131-
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APPENDIX B
LOWER HEATING VALUES OF TYPICAL WASTES
PRODUCT
Agricultural:
Butter
Cotton Seed Hulls
Grain
Egg Yolk
Egg White
Pecan Shells
Garbage:
Coffee Grounds
Corn Cobs
Corn, Shelled
Fats
Food Wastes (Dry)
Paper Products:
Brown Paper
Corrugated Boxes
Food Cartons
Magazines
Newspapers
Plastic Coated Paper
Tar Paper (30% Tar)
Waxed Milk Cartons -
Plastics :
Polyamides (Nylon)
Polyesters
Polyolef ins (Polyethlene ,
Polyproplene, etc.)
Polystyrene
Polyurethane
Polyvinyl Chloride
Plastic Film (Mixed)
Vinyl Coated Fabric
Vinyl Coated Felt
Vinyl Scrap
BTU/LB NET
15,240
7,910
7,130
13,400
9,440
8,100
9,800
7,540
8,550
15,360
7,800
7,090
6,830
7,110
4,830
7,800
7,090
10,120
10,790
11,960
11,050
'l7,500
15,650
10,580
7,280
12,740
8,200
10,170
10,500
PRODUCT
Rubber Products :
Latex
Banbury-Rubber Scrap
Raw Batch Stock
Rubber Coated Fabric
Rubber Tape
Rubber Tires
Textiles:
Cotton Batting
Uncured Duck
Rayon and Cotton Yarn
Rags
Wood:
Oak
Pine
Sawdust
Yard:
Brush
Grass
Leaves
Miscellaneous :
Paints and Oils
Leather
Linoleum
Street Sweepings
Water (1,000)
BTU/LB NE'
9,200
12,180
13,040
10,120
8,860
12,000
6,540
8,600
7,138
7,390
7,990
8,420
8,000
7,270
7,070
6,530
12,330
8,140
7,700
5,520
Minus
-132-
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APPENDIX C
STACK EMISSION TESTING DATA
EMISSIONS TEST PAHOKEE, FLORIDA INCINERATOR
1.
2.
3.
4.
5.
6.
7.
8.
9.
10
Dry Catch (Probe+
Filter) , Grams
Cond. Catch (Impingers) ,
Grams
Barometric Press. Mean
Sea Level
Stack Pressure, IN W.G.
Absolute in Mercury
Avg. Meter Temp. , Deg. F
Total # Traverse Points
Total Test Duration, Min.
Meter Conditions, Dry Gas
Sampled (Cu. ft.)
Total cu. ft. (gas) Sampled
Total cu. ft. (gas) in Stack
Std. cu. ft. Dry Gas Sampled
Molecular Wgt. of Condensate
.PHOT Correction Factor
Trial Run Test Run No. & Date
Date 123
5/12/75 5/13/75 5/14/75 5/15/75
.3484 .2558 .2898 .2558
,0118 .0467 .0553 .0276
29.97 30.00 29.98 29.96
.05 .05 .02 .02
29.96 29.99 29.97 29.95
106 105 107 110
48 48 48 48
240 270 260 263
129.047 138.499 126.308 121.060
136.402 156.728 145.786 139.858
335.22 405.325 354.704 353.517
120.839 129.821 118.116 112.536
18 18 18 18
.85 .85 .85 .85
Stack Cross Sectional Area, Sq. Ft. - 8.080
Stack Height above Ground Level, Ft. - 40
-133-
-------
STACK EMISSION TESTING DATA
EMISSIONS TEST ORLANDO, FLORIDA INCINERATOR
1.
2.
3.
4.
5.
6.
7.
8.
9.
10
Dry Catch (Probe +
Filter), Grams
Cond. Catch(Impingers) , Grams
Barometric Press. Mean Sea
Level
Stack Pressure, IN W.G.
Absolute in Mercury
Avg. Meter Temp., Deg F
Total # Traverse Points
Total Test Duration, Min.
Meter Conditions, Dry Gas
Sampled (cu. ft.)
Total cu. ft. (gas) Sampled
Total cu. ft. (gas) in Stack
Std. cu. ft. Dry Gas Sampled
Molecular Wgt. of Condensate
.PITOT Correction Factor
Trial Run
Date
5/19/75
.3466
.0177
29.99
.03
29.97
104
48
279
163.381
185.031
428.565
153.492
18
.85
Test Run No
1 2
5/20/75 5/21/75
.4323 .5375
.0265 .0196
30.02 30.04
.03 .03
30.00 30.02
108 97
48 48
240 275
158.672 167.850
181.131 195.959
463.467 520.518
147.975 159.799
18- 18
.85 .85
. & Date
3
5/22/75
.7524
.0387
30.05
.03
30.03
100
48
240
164.232
193.395
530.483
155.333
18
.85
Stack Cross Sectional Area, Sq. Ft. - 8.510
Stack Hgt. Above Ground Level, Ft. - 50
-134-
-------
STACK EMISSION TESTING DATA
EMISSIONS TEST SILOAM SPRINGS, ARKANSAS INCINERATOR
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Dry Catch (Probe +
Filter), Grams
Cond. Catch (Impingers),
Grams
Barometric Press. Mean
Sea Level
Stack Pressure, IN W.G.
Absolute in Mercury
Avg. Meter Temp., Deg. F.
Total # Traverse Points
Total Test Duration, Min.
Meter Conditions, Dry Gas
Sampled (Cu. ft.)
Total cu. ft. (gas) Sampled
Total cu. ft. (gas) in Stack
Std. cu. ft. Dry Gas Sampled
Molecular Wgt. of Condensate
PITOT Correction Factor
*
Trial Run
Date
10/2/75
.0315
.0950
30.15 30
.12
29.66 29
84 78
48 48
144 152
63.655 68
67,437 74
89.935 100
62.041 67
18 18
.35
Test Run No. & Date
1
10/3/75
.0310
.0467
.12
.12
.65
.366
,133
.882
.296
.35
2
10/3/75
.0547
.0494
30.15
.12
29.68
95
48
150
89.977
95.636
123.132
85.959
18
.35
3
10/4/75
.1072
.0297
30.00
.05
29.52
72
48
152
81.580
85.454
287.805
81.221
18
.35
Stack Cross Sectional Area, Sq. Ft. - 3.547
Stack Height above Ground Level, Ft. - 60
-135-
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APPENDIX D
LABORATORY ANALYSES FORMULAS FOR ALL SITES
Flow Chart of Sample Preparation
Original Sample
Moisture as Received(1)
Grindable Fraction(2)
Ungrindable Fraction(3)
Ash
BUT/lb
Carbon
Hydrogen
Chloride
Fixed Carbon
Nitrogen
Oxygen
Sulfur
Volatile Matter
(1) The moisture as received is on the entire sample.
(2) Results are on the grindable portion of the sample only.
(3) The non-grindable sub-sample that was not incorporated
consisted of metals and ceramics that could not pass
through grinding mills. This could be considered as
part of the ash.
-136-
-------
METHOD REFERENCES FOR SOLID WASTE & RESIDUE LABORATORY ANALYSES
ASH
ASTM D-271 Ash in Raw Refuse
BTU/LB
Parr Instrument Co., Instrument Manual, Method # 139
CARBON
ASTM Gaseous Fuels Coal and Coke D271, PP.22-25 (1971)
CHLORIDE
ASTM D2361-66
FIXED CARBON
ASTM Gaseous Fuels, Coal and Coke PP.22-25 (1971)
HYDROGEN
ASTM Gaseous Fuels, Coal and Coke, PP.22-25 (1971)
NITROGEN
ABAC 2.049* Modified
MOISTURE AS RECEIVED
ASTM D271 Moisture in Raw Refuse
MOISTURE AT ASSAY
ASTM P.271 Moisture & Volatile Solids in Raw Refuse
OXYGEN
ASTM Gaseous Fuels Coal and Coke, PP.22-25 (1971)
SULFUR
ASTM D 271-46, Vol. III-A, PP. 36-37
VOLATILE MATTER
ASTM D-271 P.16 (1971
ADAC Methods -llth ED (1970) Except Those Noted * Which are From 12th
ED (1975)
ADCS Methods From 3RD Edition (1969)
-137-
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APPENDIX E
SILOAM SPRINGS STEAM SALES AGREEMENT
AGREEMENT between the City of Siloam Springs, Arkansas, a municipal
corporation organized and existing under the laws of the State of Arkansas
(hereinafter referred to as the "City"), and the Allen Canning Company, an
Arkansas corporation, having a food processing facility located at Siloam
Springs, Arkansas, (hereinafter referred to as "Allen").
WITNESSETH:
The City is in the process of purchasing from U.S. Recycle Corp., of
Little Rock, Arkansas, a MUNICIPAL WASTE DISPOSAL SYSTEM capable of disposing
of 16 tons per 10-hour day of typical municipal refuse, including residential,
commercial and industrial, which is to include the following standard equipment
Two (2) Model C-550M CONSUMAT Systems with Loaders
In addition to the above-specified municipal waste disposal system, the
City is in the process of purchasing from U. S. Recycle Corp., a separate
ENERGY CONVERSION SYSTEM capable of supplying certain steam energy requirements
of Allen's food processing facility located at 1020 East Jefferson Street,
Siloam Springs, Arkansas, said energy conversion system to include the
following:
ENERGY CONVERSION SYSTEM: This system will utilize two (2) Wast Heat
Boilers, Four (4) modules each, Model CR5-504, as produced by Riley-Beaird,
Inc., of Shreveport, Louisiana, attached to the two (2) CONSUMAT Model C-550M's
as described above.
In consideration of the foregoing premises and the mutual agreements
hereinafter set forth, the parties agree as follows:
Section 1; Construction of System
1.1 The City will lease from Allen, the necessary land adjacent to
Allen's in-town plant, pursuant to a certain Lease Agreement between the same
parties hereto, dated the llth day of December 1974, a copy of which is
attached hereto, and this Energy Agreement and said Lease Agreement are hereby
incorporated by reference into and made a part of each separate agreement so
that performance by the parties of one agreement shall be contingent upon
performance by the parties of the other agreement. The City agrees to
-138-
-------
purchase, or provide the funds required for the purchase of, the necessary
building, waste disposal and energy conversion equipment, as hereinabove
specified, at no cost to Allen, in order to produce steam energy through the
incineration of solid waste, and to deliver such steam energy to a single
interface at a point on Allen's property to be mutually selected by both
parties hereto. The plans and specifications for such waste disposal and
energy conversion system, approved by the City, are on file in the office of
the City Clerk, and are made a part hereof by reference as fully as if written
out in toto in this Section of this Agreement. The City will transport such
steam energy to said point of delivery and tie into Allen's main steam line at
a point on Allen's steam grid system; and, further, the City will furnish, at
no cost to Allen, all appropriate pipes, lines, returns and other appurtenances
required for such'transport.
1.2 The City agrees, at its expense, to construct or have constructed
and maintain said waste disposal and energy conversion system in accordance
with the requirements of all municipal, state or federal regulations or
requirements, with such provisions for fire protection that Allen's fire
insurance rating will not be affected, and in accordance with the plans and
specifications referenced in Section 1.1 hereinabove. If construction of said
system shall result in any increase in fire insurance premiums for Allen, the
City shall pay any such increase in premiums.
1.3 The City shall complete construction of such system with due
diligence, subject only to delays caused by shortages of labor and materials,
government regulations, strikes or any other acts beyond the reasonable
control of the City.
1.4 The installations to the point of delivery made by the City at no
cost to Allen, pursuant to Section 1.1 hereinabove for the use of steam energy
at Allen's facility are to remain the property of the City, even after
termination of- this Agreement, although connected to, but not a part of,
Allen's steam grid system. Upon removal of same by the City, it will restore
the interconnection of Allen's steam grid system.
Section 2; Terms of Purchase and Sale
2.1 Allen agrees to purchase from the City all the steam energy produced
by the City up to the maximum steam energy requirements of Allen's said food
processing facility for a period of twenty (20) years, commencing on the date
of the City's first delivery of such steam energy to Allen pursuant to
-139-
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Section 1.1 hereinabove. The steam energy so generated by the City and
delivered to Allen as herein provided shall be for the sole use of Allen and
may not be resold by Allen without the express prior written consent of the
City. The City reserves the right to sell any excess steam produced by the
energy conversion system over and above Allen's maximum requirements, and not
purchased by Allen, to others if it so desires.
2.2 The City will make available to Allen at the aforesaid interface at
least 120,000 pounds of saturated steam at a minimum of 100 pounds pressure
per square inch gauge (PSIG) and up to a maximum of 150 PSIG within a 12-hour
period per day for a minimum of 240 days per year during said period of
twenty (20) years. The quality of the steam will meet all requirements now
existing or hereafter adopted of all local, state and federal governments and
other regulatory agencies, for food processing plants.
Section 3; Payment Rates and Terms
3.1 The steam energy provided by the City to Allen pursuant to the
Agreement will be measured by an orifice-type vapor flow meter at the point of
entry into Allen's steam grid system.
3.2 Allen will pay to the City for all such steam energy consumed the
sum of eight and one-half cents ($.085) per 100 pounds of saturated steam
between 100 and 150 PSIG measured at said point of entry. The sum is to be
calculated upon the basis of natural gas available to Allen at the price of
sixty cents ($.60) per m.c.f. Further, it will be increased or decreased in
direct proportion to any increases or decreases in such price of natural gas
available to Allen, effective the first day of the month following the gas
price change. Discounts will be given to Allen on the purchase of steam
energy under the following conditions:
3.2.1 As the price of natural gas increases above sixty cents ($.60)
per m.c.f., the price of steam will be discounted as in the table below:
GAS PRICE STEAM PRICE DISCOUNTED STEAM
PER M.C.F. PER 100 POUNDS DISCOUNT PRICE PER 100 POUNDS
$ 0.60 $ 0.085 0% $ 0.085
0.70 0.099 4% 0.095
0.80 0.114 8% 0.105
0.90 0.128 12% 0.113
1.00 0.142 15% 0.121
1.10 0.156 17% 0.129
1.20 0.170 19% 0.138
1.30 0.185 21% 0.146
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GAS PRICE STEAM PRICE DISCOUNTED STEAM
PER M.C.F. PER 100 POUNDS DISCOUNT PRICE PER 100 POUNDS
$ 1.40 $ 0.100 23% $ 0.153
1.50 0.213 24% 0.162
1.60 0.227 26% 0.168
1.70 0.241 27% 0.176
1.80 0.256 28% 0.184
1.90 0.270 29% 0.192
2.00 0.284 30% 0.199
2.10 0.298 31% 0.206
2.20 0.312 32% 0.212
2.30 0.327 32% 0.222
2.40 0.341 32% 0.232
2.50 0.355 33% 0.230
2.60 0.369 33% 0.247
2.70 0.383 33% 0.257
2.80 0.398 34% 0.263
2.90 0.421 34% 0.272
3.00 0.426 34% 0.281
3.10 0.440 34% 0.290
3.20 0.454 35% 0.295
3.30 0.469 35% 0.305
3.40 0.483 35% 0.314
3.50 0.498 35% 0.323
The discount will be 35% for all gas prices above $3.50 per m.c.f.
3.2.2 If Allen uses more than the base amount (25 million pounds)
of steam each year, the price of steam will be discounted at year's end
according to the table below:
STEAM CONSUMPTION STEAM PRICE DISCOUNTED STEAM
MILLIONS OF LBS. PER 100 LBS. DISCOUNT PRICE PER 100 POUNDS
25 $ 0.085 0% $ 0.085
30 0.085 5% 0.080
35 0.085 10% 0.077
40 0.085 15% 0.072
The discount will be 15% for all steam consumed above 40 million pounds.
3.3 The parties agree that Allen will pay to the City for such steam
energy no less than the minimum sum of $20,000.00 per year, except as provided
in Sections 4.5, 4.6, 4.7 and 4.8 hereinbelow in connection with the
interruption of service. The parties understand that such annual payment is
calculated on the basis of natural gas available to Allen at the price of
sixty cents ($0.60) per m.c.f.; and therefore, agree that such payment will be
increased or decreased in direct proportion to any increases or decreases in
such price of natural gas available to Allen, computed on the basis of the
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average annual cost of such natural gas. The normal charges for such metered
steam used by Allen will be billed monthly to Allen by the City, and any
balance remaining due to the above referenced minimum payment will be billed
annually.
3.4 Credit will be given Allen by the City for any Allen wastewater used
in the energy conversion sytem.
3.5 All payments will be due from Allen to the City within ten (10) days
of the billing date. The City may charge a 10% late charge on any bill not
paid within said ten (10) day period; and, if such billing is not timely paid
with late charge within fifteen (15) days of the billing date, the City may
discontinue service upon not less than five (5) days written notice to Allen.
No such discontinuation of service shall render the City liable for damages
or relieve Allen from performance of its obligations hereunder; and the City
reserves the right in any event, to insist upon specific performance by Allen
of its obligations under this Agreement or to claim damages.
Section 4; Operation of Heat Recovery System
4.1 The City agrees to establish by lawful ordinance a Sanitation
Facilities Commission, the membership of which shall consist of not more than
five persons, of which at least two members shall be representatives
designated by Allen. The function of this commission shall be as liaison
between the City Council and the management of the waste disposal and energy
conversion system.
4.2 The City agrees to contract for the operation of the plant and
energy conversion system at least five days per week from 7:00 a.m. Monday
through 6:00 p.m. Friday; and, further, to make steam produced by such system
available for use by Allen during such specified time period at the minimum
rate of 10,000 pounds of saturated steam between 100 and 150 pounds pressure
per square inch (PSIG) per hour.
4.3 The City agrees to contract for proper maintenance of the heat
recovery system in order to avoid any unnecessary interruption of service to
Allen.
4.4 The City agrees to give Allen sufficient notice of any interruption
of service required for the making of necessary repairs, installations or
Improvements to the system in order to afford Allen the opportunity to connect
its service facilities to other sources of energy supply.
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4.5 The City agrees to give Allen ninety (90) days written notice if
for some reason (other than for delinquent payment) the City must discontinue
service to Allen from this plant.
4.6 If proper notice is given by the City to Allen as hereinabove
indicated, the City shall not be liable to Allen for damages resulting from
the termination or interruption of service required for the making of necessary
repairs, installations or improvements or any other reasonable cause beyond
the control of the City. However, in the event of any such interruption of
service, the minimum annual payment required of Allen in the amount of
$20,000.00, or as adjusted, pursuant to Section 3.3 shall be reduced
proportionately on the basis of the number of days of interrupted service
resulting in less than two hundred forty (240) days of operation per annum.
4.7 In the event Allen's plant or the City's Waste Disposal and Energy
Conversion System shall be damaged or destroyed or their operations interrupted
by Act of God, fire, other acts of the elements, riots, civil disorder, war or
any other cause beyond the reasonable control of Allen or the City, then in
such event either party hereto shall be relieved from performance under this
agreement, including payment of minimum annual energy charges by Allen, until
normal operations are restored.
4.8 The City shall be responsible for performance of its obligations
under this Agreement or the Lease Agreement referred to above, even though the
City may have contracted with a third party for performance of all or part of
its obligations. Failure by the City to fully perform its obligations under
both of said agreements shall relieve Allen of its obligations hereunder also.
Section 5; Amendment of Agreement
This Agreement supersedes all prior negotiations and oral understandings,
if any, and may not be amended or supplemented except by an instrument in
writing signed by both parties hereto.
Section 6: Assignment
This Agreement shall be binding upon and inure to the benefit of the
parties hereto and their respective successors and assigns to which this
Agreement relates. Allen shaj.i have the right to transfer its interest under
this Agreement to any affiliated or successor legal entity subject to all of
the terms and conditions of this Agreement.
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Section 7; Effective Date
This agreement shall be in full force and effect only upon approval by
written resolution duly adopted by the City Council at a regular or special
meeting legally called and held.
IN WITNESS WHEREOF, the parties hereunto have caused this Agreement to
be duly executed this llth day of December, 1974.
CITY OF SILOAM SPRINGS, ARKANSAS
BY:
MAYOR
(SEAL)
ATTEST:
ALLEN CANNING COMPANY
BY:
PRESIDENT
(SEAL)
ATTEST:
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APPENDIX F
ENERGY CONVERSION FORMULAS
HEAT RELEASE
Municipal Waste, "As Received" 3,000 - 6,000 Btu/Lb.
Hospital Waste, Milled and Mixed .... 6,000 - 9,500 Btu/Lb.
Coal 10,500 - 14,100 Btu/Lb.
#2 Oil 138,500 Btu/Gal.
Natural Gas 970 - 1,030 Btu/Cu. Ft.
@ 4 O5z psig Std. Measure
100,000 Btu/Therm
(100 Cu. Ft.)
Propane 2,590 Btu/Cu.Ft.
DENSITIES
Municipal Waste, "As Received" 5 - 14 Lbs./Cu. Ft.
Municipal Waste, Combustible Portion ... 4-8 Lbs./Cu. Ft.
Hospital Waste, Milled and Mixed 3.5-6.5 Lbs./Cu. Ft.
Coal 40 - 44.4 Lbs./Cu. Ft.
#2 Oil 57.1 - 64.5 Lbs./Cu, Ft.
Residue, Municipal Waste 38-55 Lbs./Cu. Ft.
STEAM PRODUCTION
100 Lb. Steam at 100 psig requires 100,000 Btu average
@ 100% Efficiency Energy Transfer.
@ 75% Transfer Efficiency requires 133,333 Btu
1 Btu = 1 Ib. water raised 1 F.
= .0010306 Ib. steam with feed water @ 212°F.
1 Boiler Horsepower (BHP) = 33,475.3 Btu/Hr. Heat to Steam
= 34.5 Lb. Steam evaporated
per hour from 212 F.
= 44,633 Btu/Hr. Fuel Input
@ 75% Transfer Efficiency
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