United States Office of Water & sw-797
Environmental Protection Waste Management November 1979
Agency Washington D.C. 20460
Sol id Waste
vvEPA Small Modular
Incinerator Systems
with Heat Recovery
A Technical, Environmental,
and Economic Evaluation —
Executive Summary
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SMALL MODULAR INCINERATOR SYSTEMS WITH HEAT RECOVERY:
A TECHNICAL, ENVIRONMENTAL, AND ECONOMIC EVALUATION
Executive Summary
This report (SW-797) was prepared
under contract for the Office of Solid Waste
by Richard Frounfelker.
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
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An environmental protection publication (SW-797) in the solid waste
management series. Mention of commercial products does not constitute
endorsement by the U.S. Government. Editing and technical content of this
report were the responsibilities of the Resource Recovery Division of the
Office of Solid Waste.
Single copies of this publication are available from Solid Waste
Information, U.S. Environmental Protection Agency, Cincinnati, OH 45268.
ii
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FOREWORD
This report is a summary of a technical, environmental, and economic
evaluation of two small modular incineration-heat recovery facilities: one
in the plant of the Truck Axle Division of Rockwell International Corporation
in Marysville, Ohio, and the other in the Municipal North Shore Energy Plant
in North Little Rock, Arkansas. The evaluation program was sponsored and
directed by the Environmental Protection Agency (EPA) and the California
State Solid Waste Management Board and was conducted under EPA Contract
No. 68-01-3889 by Systems Technology Corporation (SYSTECH), Xenia, Ohio.
The report was prepared by Richard Frounfelker, Staff Engineer of SYSTECH,
for submittal to EPA.
The report explains the controlled air concept of the modern two-
chamber incinerator, chronicles its development and application, and sum-
marizes currently available systems for small-scale usage. Then the report
details each of two facilities selected for the evaluation and presents the
technical, environmental, and economic evaluation for each facility. In
addition, the report projects the operating costs for the two facilities under
optimum operating conditions and for municipal and industrial facilities in
general.
Since the two evaluated facilities operate under different conditions
with one burning municipal waste and the other industrial waste, they were
not compared. Moreover, the reader is cautioned not to draw comparative
conclusions.
The full report, intended for design engineers and other specialists
requiring in-depth data, will be made available for purchase from the
National Technical Information Service, Springfield, VA 22161.
111
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ABSTRACT
This program involved a technical, environmental, and economic assess-
ment of the feasibility of utilizing small modular incinerator systems for
solid waste disposal in municipal and industrial applications. The assess-
ment was implemented by (1) overviewing the state-of-the-art, (2) selecting
two operational sites (one municipal and one industrial) representative of
the state-of-the-art, and (3) subjecting these two sites to a rigorous field
evaluation. The two facilities selected for this study were a municipal
incinerator plant with a Consumat system in North Little Rock, Arkansas, and
an industrial incinerator facility with a Kelley system in the plant of the
Truck Axle Division of the Rockwell International Corporation in Marysville,
Ohio. This selection was the result of a nationwide survey to find those
two facilities which best satisfied several criteria. The principal selec-
tion requirements were a solid waste processing module with heat recovery
and a capacity of 50 tons or less per day and its being representative of
current technology, designs, and operational procedures.
Preparatory to the detailed description and evaluation of the two
facilities, the report explains the controlled air concept of the two-
chamber incinerator and briefly discribes its development and application.
In addition, as a technical guide for the review and selection of currently
available systems, the report details, according to available information,
the 17 sources whose modular incinerators represent state-of-the-art
technologies.
The technical evaluation presents the results of three weekly field
tests at each site. The data was used to calculate the following for each
system: the mass balance, the incinerator efficiency, the energy balance,
the heat recovery efficiency, and the overall effectiveness of the system as
a solid waste disposal facility.
The environmental evaluation presents the effects of the incinerator-
heat recovery operation on the environment, specifically the atmosphere, the
discharged process water, the landfills for refuse disposal, and the plant
areas. An EPA Level One assessment presents a detailed analysis of the
emissions.
The economic evaluation presents a detailed accounting of facility
(1) capital costs, (2) operating and maintenance costs, (3) revenues, and
(4) net operating costs.
Since the two systems differ in many respects and operate on dissimilar
waste streams, they are not compared.
This report was submitted in fulfillment of Contract Number 68-01-3889
by Systems Technology Corporation under the sponsorship of the U.S. Environ-
mental Protection Agency. This report covers the period October 1977 to
March 1979.
IV
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CONTENTS
Foreword ..... iii
Abstract iv
Figures vii
Tables x
Acknowledgment xii
1. Introduction and Summary 1
Program objective, background, and scope 1
Current modular incinerator technology 2
Concept 2
Current systems 2
Summary of selected systems 3
Technical capabilities 3
Environmental acceptability 4
Economic effectiveness 4
2. The Small Modular Incinerator 6
Controlled air incineration 6
Introduction 6
Feeding mechanism 7
Primary chamber 8
Secondary chamber 8
Temperature control 8
Residue removal 9
Energy recovery 9
Waste consumption 9
Stack emissions 9
History of controlled air incineration 10
Introduction 10
Design evolution 10
Currently available modular incinerators 11
3. Overview of Facilities and Their Evaluations 19
Evaluation Overview 19
North Little Rock facility 19
Description 19
Operation 21
Introduction to test program 24
Technical evaluation 25
Environmental evaluation 31
Economic evaluation 38
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CONTENTS (concluded)
Marysville facility 42
Description 42
Operation 47
Introduction to test program 47
Technical evaluation 47
Environmental Evaluation 53
Economic evaluation 56
4. Operating Cost Projections 60
Evaluated facilities 60
Facilities in general 60
VI
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FIGURES
Number Page
1 Operational ranges (stoichiometric air percentage and
temperature) for controlled air incinerators 7
2 Configuration of two horizontal cylindrical
chambers with one above the other . 14
3 Configuration of two horizontal rectangular chambers
with one above the other 14
4 Configuration of Burn-Zol's two vertical cylindrical
chambers with one above the other 15
5 Configuration of Lamb-Cargate's two vertical cylindrical
chambers with one above the other 16
6 Configuration of Scientific Energy Engineering's
incinerator with an auger in the primary chamber 17
7 Configuration of Giery's incinerator with a rotary
grate in the primary chamber - . . . . 17
8 Configuration of C. E. Bartlett's incinerator with a
rotary primary chamber 18
9 Configuration of Clear Air's incinerator-heat recovery
system with two horizontal rectangular chambers aligned
one after the other 18
10 Vicinity map of North Little Rock facility 20
11 Plant layout of North Little Rock facility 21
12 Three-dimensional drawing of incineration-heat recovery
module in North Little Rock facility 22
13 Cross section of incinerator module in North Little
Rock facility 23
14 Flow diagram of incineration-heat recovery processes in
North Little Rock facility 24
Vll
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FIGURES (continued)
Number Page
15 Mass balance for incineration-heat recovery processes in
North Little Rock facility during the 118.5-hour October
field test 27
16 Energy balance for incineration-heat recovery processes in
North Little Rock facility during the 118.5-hour October
field test 28
17 System temperature versus loading sizes and events in North
Little Rock facility 29
18 Stack emission during heavy and light loading periods in
North Little Rock facility 30
19 In-plant noise-level plot for North Little Rock facility. . 35
20 Outside-plant noise-level plot for North Little Rock
facility 36
21 Vicinity map of Marysville (Rockwell International)
facility 42
22 Functional schematic of incineration-heat recovery
processes in Marysville facility 43
23 Three-dimensional, cutaway drawing of incinerator
module in Marysville facility 44
24 Plant layout of Marysville facility 45
25 Flow diagram of incineration-heat recovery processes in
Marysville facility 46
26 Mass balance for incineration-heat recovery processes
in Marysville facility during the 120-hour (75.5-hour heat
recovery) July field test 49
27 Energy balance for incineration-heat recovery processes in
Marysville facility during the 120-hour (75.5-hour heat
recovery) July field test 50
28 System temperatures during peak loading periods in
Marysville facility 51
viii
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FIGURES (concluded)
Number Page
29 Stack emissions during peak loading periods in
Marysville facility 52
30 In-plant noise-level plot for Marysville facility 56
31 Estimated operating cost as a function of refuse feed rate,
shifts per week, and operating percentage of rated capacity
for municipal small modular incinerators 64
32 Estimated operating cost as a function of refuse feed
rate, shifts per week, and operating percentage of rated
capacity for industrial small modular incinerators .... 65
IX
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TABLES
Number Page
1 Manufacturers of Modular Incinerators 12
2 Addresses and Telephone Numbers of Modular
Incinerator Manufacturers 13
3 North Little Rock Weekly Refuse Composition for
March, May, and October Tests 26
4 North Little Rock Pollutant Emission Rates for
October Test 31
5 North Little Rock Summary of Stack Emissions for
March, May, and October Tests 32
6 North Little Rock Residue Leachate Parameter and
Component Values 34
7 North Little Rock Summary of Elements Detected in
Stack Emission Filters 37
8 North Little Rock Actual Capital Costs 38
9 North Little Rock Unit Cost Data 39
10 North Little Rock Projected Annual Operating and
Maintenance Costs 40
11 North Little Rock Projected Annual Revenues 41
12 North Little Rock Projected Annual Net Operating Costs . . 41
13 Marysville Weekly Refuse Composition for April,
July, and August Tests 48
14 Marysville Pollutant Emission Rates for July Test 53
15 Marysville Summary of Stack Emissions for April, July,
and August Tests 54
16 Marysville Residue Leachate Parameter and Component
Values 55
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TABLES (concluded)
Number Page
17 Marysville Summary of Elements Detected in Stack
Emission Filters 57
18 Marysville Capital Costs 57
19 Marysville Unit Cost Data 58
20 Marysville Projected Annual Operating and Maintenance
Costs per Cost Center 59
21 Marysville Net Operating Cost by System Function 59
22 North Little Rock Projected Optimum Operating and
Maintenance Costs 61
23 North Little Rock Projected Optimum Annual Revenues .... 61
24 Marysville Projected Optimum Operating and Maintenance
Costs 62
25 Marysville Projected Optimum Net Operation Cost 62
XI
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ACKNOWLEDGMENT
This evaluation program was performed under EPA Contract No. 68-01-3889,
"Technical and Economic Evaluation of Small Modular Incinerator Systems with
Heat Recovery."
The EPA project officer was David B. Sussman of the Office of Solid
Waste, Washington, D.C. The coordinator for the California State Solid
Waste Management Board was Robert Harper, Waste Management Engineer.
On behalf of Systems Technology Corporation, the author is pleased to
acknowledge the guidance and support of David B. Sussman and Robert Harper
and the cooperation of the plant engineers and staff members and the manu-
facturer representatives who generously assisted with the testing at the
Rockwell International Corporation facility in Marysville, Ohio, and at the
North Shore Energy Plant in North Little Rock, Arkansas.
The author is also grateful to Arthur Young & Company for its collabo-
ration in the economic evaluation and to all his company colleagues who
contributed to the collection of the test data and the development of this
report. Of the latter, the author is particularly thankful to Gerald Degler,
Ned Kleinhenz, and Rick Haverland.
xii
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SECTION 1
INTRODUCTION AND SUMMARY
PROGRAM OBJECTIVE, BACKGROUND, AND SCOPE
This study consisted of a technical, environmental, and economic evalua-
tion of small modular incinerator systems with the overall objective being to
determine the feasibility of their usage for solid waste disposal and -heat
recovery in municipal and industrial environments. The evaluation aspects of
this report include (1) sufficient data and procedures to assess all technical,
environmental, and economic aspects of small modular incineration-heat recovery
systems; (2) a technical guide for the review and selection of currently
available systems; (3) sufficient manufacturer and field test data to apply
and/or adaptf the current systems to particular needs; and (4) a data base for
the future analysis and appraisal of advanced systems.
Recent technological advances and economic and environmental develop-
ments prompted the Office of Solid Waste Management of the Environmental
Protection Agency to initiate this study. Some of the more significant
advances are as follows: First, the incinerator manufacturers have success-
fully developed the two-chamber, controlled air incinerator for optimum
efficiency and significantly reduced particulate emissions. Second, they
have designed incinerators with integrated control systems to ensure their
economic feasibility and efficient operation. Third, the small modular
incinerator features simple and reliable operation, low maintenance costs,
and payback frequently within 3 to 4 years (primarily in an industrial
application).
Several economic and environmental factors have given added impetus to
the attractiveness of the small modular incinerator with heat recovery. For
example, municipalities are finding that such incinerators can address the
problems (1) of rising landfill costs or rapidly diminishing landfill sites,
(2) of complying with environmental pollution control regulations, and (3) of
offsetting capital costs for waste disposal equipment through the revenues of
recovered energy products and the savings of eliminated landfill expenses.
Similarly, industries are seeing the advantages of burning waste rather than
oil or gas (1) to recover the waste energy, (2) to save the expenditures for
landfill disposal, (3) to meet the threats of fuel curtailments and rising
costs, (4) to gain tax credits, and (5) to comply more readily with environmen-
tal control regulations. Furthermore, public opinion and government enactments
lend strong encouragement and support to the widespread usage of the small
modular incinerator with heat recovery because of its resource recovery and
environmental control potential.
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This report explains the controlled air concept of the modern two-
chamber incinerator, chronicles its development and application, and summarizes
currently available systems designed for small-scale usage. Then the report
details each of two selected small-scale facilities and presents the technical,
environmental, and economic evaluation of each, but in no way attempts to com-
pare the two different systems. Finally, the 1978 economic data of the two
evaluated facilities were adapted to estimate the operating costs at municipal
and industrial facilities in general.
The two small incinerator facilities selected for intensive evaluation
were a municipal incinerator plant in North Little Rock, Arkansas, and an
industrial incinerator in the plant of the Truck Axle Division of the Rockwell
International Corporation in Marysville, Ohio. In the selection of the two
facilities, each had to meet three criteria: (1) a capacity designed for
50 tons or less of solid waste per day; (2) its integration with heat recovery
equipment; and (3) its incorporation of the principles, designs, and operational
procedures of current technology.
CURRENT MODULAR INCINERATOR TECHNOLOGY
Concept
The modular incinerators, generally consisting, of a primary and a second-
ary combustion chamber, employ controlled air techniques to reduce the amount
of air required for combustion in the primary chamber and to lower the level
of their particulate emissions. These incinerators originated in the late
1960's, and their technologies and applications expanded in the 1970's.
The name "modular" was derived from the following: (1) each unit is
identical, (2) each unit operates independently, and (3) one or more units
can be readily integrated in an existing system as the waste demand increases.
The terms "starved air," "substoichiometric," and "pyrolitic" denote the
different combustion processes in the primary chamber. Sometimes these terms
are used to denote the entire incinerator system.
Current Systems
A survey identified 16 manufacturers that produce incinerators capable of
processing 454 to 1816 kg/hr (1000 to 4000 Ib/hr) of industrial and/or munici-
pal solid waste and of recovering the heat for energy production. The primary
chambers in these incinerators operate under starved air (substoichiometric)
or excess air combustion conditions. The incinerator systems can be grouped in
five basic physical configurations. The larger systems have (1) automatic feeds
consisting of loading hoppers, conveyors, and screws; (2) loading rams, moving
grates, augers, and rotating chambers for continuous refuse flow through the
primary chamber; and (3) heat recovery systems with fire or water tube boilers
and other heat exchangers.
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SUMMARY OF SELECTED SYSTEMS
Technical Capabilities
Performance—
At the North Little Rock municipal facility, where a Consumat incineration-
heat recovery system is operative, the Consumat module proved capable of
recovering about 55 percent of the energy burned and of reducing the municipal
solid waste 55 percent by weight and 94 percent by volume. Over the past
3 years, 13 Consumat incinerators have been burning municipal waste. Four of
these incinerators are integrated with heat recovery equipment.
At the Marysville industrial facility, where a Kelley incineration-heat
recovery system is operative, the Kelley module proved capable of recovering
about 55 percent of the energy burned and of reducing industrial refuse
95 percent by volume. Over the past four years, seven similar systems have
been burning industrial waste. In addition, four units are burning municipal
waste but without heat recovery.
The designs of both systems are still evolving. Each new facility
introduces technological advances based on the experience gained from the
previous installations. These technological improvements have advanced to
the stage where the systems can burn waste and produce energy with satisfactory
reliability.
Maintenance and Reliability—
The routine maintenance of both the Consumat and the Kelley systems
consists principally of small refractory repairs and replacement of thermo-
couples and other switches, door seals, and motors. The maintenance require-
ments specific to each system are the weekly removal of soot from the boiler
tubes in the Consumat system and the weekly cleaning of the induced draft fan
blades and at least the semiannual cleaning of the boiler tubes in the Kelley
system. The major maintenance requirement of both systems is the refractory
replacement in 3 to 8 years, depending on the operational mode. In addition,
because of its more extensive control system, the Consumat module requires
more maintenance on the automatic control, hydraulic, and residue removal
systems. In general, modules burning municipal waste require more maintenance
than those burning industrial refuse. In addition, more operational interrup-
tions must be anticipated when burning municipal waste because of the jams
caused by large metal objects in the waste and the greater frequency of the
above-mentioned routine maintenance. Moreover, the slag formed from the
fusion of glass and metals frequently plugs air injection ports and degrades
the refractory.
Operation—
The Consumat system with its 100-TPD capacity at the North Little Rock
facility required nine personnel: one supervisor, one clerk, one truck
driver, and two operators for each of three shifts. The Kelley system at the
Marysville facility with its capacity of 12 TPD and limited operational usage
of two shifts, 5 days per week, required only one full-time operator per
shift. As additional part-time assistance was required, it was usually supplied
by the plant maintenance staff. Neither facility required waste preprocessing,
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although operators at both facilities removed such materials as pipe and wire
before refuse loading and hand-loaded some materials into the incinerator
hopper to prevent jamming.
The Consumat system includes (1) a remotely controlled display panel to
instruct the loading operator on how large a load to collect and when to
deposit it into the incinerator hopper, (2) an automatically modulated air
control to maintain a desired temperature in each of the two combustion
chambers, and (3) an automatic ash removal system. The Kelley system allows
the operator to judge the size and frequency of each refuse loading. With
the airflow preset to handle a specific waste stream, only a high temperature
lockout on the Kelley system prevents extreme refuse overloading. In both
systems, overfeeding causes high temperatures in the secondary chamber,
excessive gaseous emissions, and wasted energy. On the other hand, under-
feeding reduces the system throughput rate, and the resultant low chamber
temperatures may require burning auxiliary fuel. Therefore, proper feeding
of the incinerators to ensure proper combustion is essential for optimum
incinerator performance.
Environmental Acceptability
Emissions Compliance—
Neither facility had a high enough daily refuse consumption, i.e., over
50 tons per day per module or 250 tons per day per facility, to be considered
under the Federal standard of performance for new stationary sources or the
prevention of significant deterioration regulations. Therefore, a new source
review was not required during the preconstruction planning. Both plants
complied with their respective state-imposed emissions standards and building
permits. If either facility had more than a daily 250-ton throughput, it
would have been subject to a new source review and would have required the
best available emissions control such as an electrostatic precipitator or a
fabric filter.
At both facilities, the gaseous emissions related directly to the size
of the load fed into the incinerator. The sulfur and nitrogen oxide levels
in the stack emissions were negligible. At the North Little Rock facility,
the chloride emissions varied from 100 to 600 mg/m3. No direct relationship
was evidenced between the loading or sizing of the particulate emissions and
the modulating air supply.
EPA Level 1 Analysis—
At both facilities, 90 percent of the stack particulates were less than
7 micrometers in diameter; the stack emissions had a wide range of metals and
halogens in minute amounts; and the residue had a high pH and contained
traces of many metals such as zinc, tin, lead, and cadmium.
Economic Effectiveness
Capital Cost—
For an incinerator with heat recovery, the capital cost of refuse
processed daily was computed at $15,000 per ton (based on. 1977 dollars).
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The relationship between the capital cost per ton and the incinerator capacity
was found to be nearly linear up to a 200-TPD capacity. A 12-TPD industrial
system would cost $220,000 to $300,000, while a 100-TPD municipal system with
a 300-meter steam condensate return line would cost about $1,500,000 (based
on 1977 dollars).
Operational Cost—
On the basis of the test data, the optimum annual operating cost (based
on 1978 dollars) of a 100-TPD municipal facility would be $370,000. With
optimum steam revenues and tipping fees of $305,000, the net annual operating
cost of this facility would be $65,000 or $3.01/Mg ($2.72/ton) of refuse
processed. For a 12-TPD industrial facility, the optimum annual operating
cost (based on 1978 dollars) would be $117,944. Applying credits for disposal
savings and energy savings of $82,620 and $139,594, respectively, results in a
net savings of $104,270 or $31.94/Mg ($28.96/ton) of refuse processed. The
facility finances are highly sensitive to the refuse processing rate, the
operating time, and the steam sales price.
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SECTION 2
THE SMALL MODULAR INCINERATOR
CONTROLLED AIR INCINERATION
Introduction
During the 1960's virtually all operational incinerators were still
uncontrolled air units. To ensure a high degree of combustion in these
incinerators, air was supplied in fixed amounts with a volume considerably
more than that required for stoichiometric combustion. Consequently, large
quantities of both combustible and inert particulates were discharged to
the atmosphere with the exiting flue gases.
In the late 1960's the industry introduced the controlled air inciner-
ator, that is, an incinerator with an afterburner or an incinerator with a
primary and a secondary combustion chamber. The term "controlled air"
denotes that the air flowing into the two combustion chambers is regulated
at a minimum rate. The lower airflow requires less motor horsepower on the
fans and reduces the amount of the particulates entrained in the exiting
flue gases.
The first, or primary, chamber is also called the lower chamber, the
combustion chamber, or the gasifier. Similarly, the second, or secondary,
chamber is also called the upper chamber, the ignition chamber, the after-
burner, or the thermal reactor.
The term "modular" as a descriptor for the controlled air incinerator
developed as follows: The controlled air incinerators designed for burning
commercial and industrial waste have been constructed of integral components,
one for the primary chamber, one for the secondary chamber, and so on.
Each component has been assembled and packaged in the factory for immediate
on-site installation. Only electrical, fuel, water, and gas duct connections
are required at the installation site. When the waste volume has exceeded
the capacity of the installed units, additional incinerators have been
incorporated to meet the increased demand. Since the additional incinerators
are constructed and function as modules, the integrated units became known as
modular incinerators. While the capacity of the modular incinerators has
increased from 1 to 4 tons of waste per hour, most of the components are
still completely assembled and packaged in the factory for immediate on-site
installation.
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Controlled air incinerators are grouped under two main categories
according to the degree of combustion, complete or partial, in the primary
chamber. Since the complete combustion requires excess air and the partial
combustion needs substoichiometric conditions, the categories are excess air
incinerators and substoichiometric, or starved air, incinerators (see Figure 1)
EXCESS AIR —percent
0 100 200
300
4000
3000
LLJ
CL
DC
W 2000
1000
STARVED AIR RANGE
. • • PRIMARY COMBUSTION CHAMBER
SECONDARY COMBUSTON CHAMBER
EXCESS AIR RANGE
PRIMARY AND SECONDARY
COMBUSTION CHAMBERS
2000
1500
1000
o
LU
DC
DC
LU
Q.
5
LU
500
100
200
300
400
STOICHIOMETRIC AIR — percent
Figure 1. Operational ranges (stoichiometr,ic air percentage and
temperature) for controlled air incinerators.
In addition to the airflow regulation, the combustion process is also
controlled by varying the waste feed rate and, in some incinerators, by
spraying water into the primary chamber.
Feeding Mechanism
The waste to be burned is fed into the primary chamber in controlled
batches and at prescribed intervals. The feed rate is usually dictated by
the temperature in the secondary chamber. Except for the removal of white
goods and large metals, the waste stream usually need not be preprocessed
before it enters the primary chamber.
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Primary Chamber
During start-up of the substoichiometric, or starved air, incinerator,
one or two auxiliary burners in the primary chamber progressively dry,
volatize, and ignite the waste. When the combustion rate is sufficient to
sustain partial oxidation reactions, the auxiliary burners are shut off. The
partial oxidation is maintained by supplying the primary chamber with less
air than that needed for the complete combustion of the gases and chars. The
combustible gases and particulates generated in the primary chamber flow into
the secondary chamber where combustion is completed. Any unburned carbon in
the primary chamber is removed with the ash and other inert materials.
During start-up of the excess air incinerator, an auxiliary burner in
the primary chamber dries, volatizes, and ignites the waste. With 75 to
150 percent excess air introduced under, over, and beside the waste, the
combustion is sustained sufficiently to turn off the burner and to burn both
the gas by-products and the combustible solids of the initial and subsequent
waste batches. As the gases flow into and through the secondary chamber, any
remaining combustibles are burned to completion.
Secondary Chamber
In the substoichiometric, or starved air, incinerator, the secondary
chamber is initially heated by an auxiliary burner. This burner ignites the
partially oxidized combustibles flowing from the primary chamber into the
secondary chamber. Then as the burning gases mix with additional air,
complete combustion is achieved and the flue gas temperatures increase to
760° and 888°C (1400° and 1600°F). As the combustion generating this heat is
self-sustaining, the burner is automatically shut off by a temperature control
device and remains off while the unit is maintained at the designed operating
level.
In the excess air incinerator, no auxiliary burner is needed in the
secondary chamber since the high temperature of the entering gases and the
addition of more air is sufficient to sustain combustion. The excess air
introduced into the chamber ranges from 75 to 150 percent of the air needed
for combustion. Excess air, turbulence, and retention time collectively
provide the conditions for the nearly complete burning of all the combustible
gases and particulates.
Temperature Control
The temperature in the primary chamber is sensed by thermocouples.
Temperature control is maintained at a set point with a 37.7°C (100°F)
control band by varying the waste feed rate and the amount of air injected
and by spraying the chamber with a water mist. While the set points vary
with the incinerator manufacturer and the waste to be burned, they generally
range from 649° to 982°C (1200° to 1800°F).
The temperature in the secondary chamber is also sensed by thermocouples
with set points. When the chamber temperature reaches the set points, the
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thermocouples activate controllers which modulate airflow dampers and turn
the burner on and off.
Residue Removal
Ash and other noncombustible residue which settle on the hearth of the
primary chamber after the combustion process are periodically removed by
manually or automatically operated systems. In the manual system the operator
scoops out the ash (by shovel or front-end loader) after the unit has been
shut off and cooled down. In the automatic system the ash is pushed or
forced ahead of the burning waste until it exits the chamber, generally
through a drop chute into a water-sealed pit or an air-lock chamber.
Energy Recovery
Several incinerator systems incorporate water of fire tube boilers to
recover the thermal energy from the flue gases exiting the secondary chamber.
Either an induced draft fan in the gas stream or an aspirator fan outside the
gas stream draws the flue gas through the boiler.
Waste Consumption
The waste consumption capacity of the controlled air incinerators
varies greatly with the waste characteristics. The energy content is the
most important factor in determining the capacity. The modular units are
designed to burn a specific amount of energy per hour; therefore, the higher
the energy content per unit mass, the slower the feed rate. The incinerator
capacities in industrial plants and those in municipal plants are convention-
ally expressed in waste feed rates of kilograms (pounds) per hour and mega-
grams (tons) per day, respectively.
The capacities of the substoichiometric, or starved air, incinerators
range from 10.9 to 45.4 Mg/day (12 to 50 TPD) while those of the excess air
incinerators range from 10.9 to 272.1 Mg/day (12 to 300 TPD).
Stack Emissions
Since the controlled air combustion in the two chambers burns most, but
not all, of the combustible gases and particulates, the stack emissions without
any additional air pollution equipment will contain some unburned carbon, as
well as inert particles and vapors.
Industrial incinerators that burn a consistent waste have been designed
and operated so that their stacks would not require additional emission
control equipment. In contrast, municipal incinerators that burn a highly
heterogeneous and changing waste may require additional air emission control
equipment to meet the applicable state standard since it is difficult to
maintain combustion at steady-state conditions, and, consequently, to keep
emissions at prescribed levels.
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HISTORY OF CONTROLLED AIR INCINERATION
Introduction
During the period from 1960 to 1970, incineration was a recognized
economical method of solid waste disposal. A reported 265 to 299 incineration
plants were in operation across the United States.
The enactment of the Clean Air Act in 1970 began the closure of the
incineration facilities because of a reluctance on the part of the facility
owners to add air pollution control equipment to meet the more stringent air
emissions standards. Closure due to the excessive cost of installing air
emission control devices has prompted most cities to seek a more economical
method of solid waste disposal.
As the incineration facilities closed, many of the incinerator companies
also folded. As the uncontrolled (excess) air incinerator industry dimin-
ished, the controlled air incinerator business correspondingly increased.
Many of the smaller modular incinerators were first developed by manufac-
turers of the larger uncontrolled air incinerators.
Design Evolution
The first-generation models of the controlled air modular incinerator
were small refractory-brick-lined primary chambers with a vertical after-
burner chamber and stack combination. These incinerators had capacities in
the range of 45.4 to 318 kg/hr (100 to 700 Ib/hr) when burning commercial or
industrial waste. The controls on these incinerators were minimal, i.e.,
on/off switches for the burner and preset air blowers. The primary uses for
the incinerators were to burn waste generated from hospitals, stores, and
restaurants.
Subsequently, the afterburner stack was replaced by a larger secondary
chamber, and the capacity of the units was increased to 1135 kg/hr (2,500 Ib/hr)
The control of the temperature and airflow in the secondary chamber permitted
modulating the burner or even shutting it off after a temperature high enough
for self-sustaining combustion of the gases was reached. This control mini-
mized the consumption of auxiliary fuel since continuously operating units do
not require afterburner fuel once they have reached operating temperature and
are maintained at designed operating levels.
The earlier units were loaded through a door before the unit was ignited.
Because of the positive pressure in the chamber and the presence of pyrolysis
gases, opening the door while the waste was burning resulted in flames leaping
out. Double doors and temperature lockouts were developed to prevent the
operator from being injured by these flames. Later, a slight negative
pressure was induced in some models to prevent flame escape as the doors were
opened. On the larger units, the loading system advanced from the door
loaders to an enclosed hopper and ram module. The latter equipment allowed
10
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more waste to be quickly and safely loaded into the primary chamber. Pneumatic
feeds for small-particle waste and pump feeds for liquid waste were also
developed.
Ash in the primary chamber was originally removed manually after the
chamber had cooled sufficiently. While automatic, continuously operating
residue removal systems have been developed for the larger incinerators, most
of the smaller incinerators (those with capacities less than 317.8 kg/hr
[700 lb/hr]) still have the ash removed manually.
Although the larger modular incinerators were integrated with heat
recovery systems, their high cost initially made their sale difficult.
However, with oil and gas prices increasing and curtailments brought on by
the recent energy crisis, the waste incinerator with heat recovery became an
economical alternative to landfills and conventional fuels. Incorporating
the heat recovery system with the incinerator necessitated the addition of
expanded control systems.
CURRENTLY AVAILABLE MODULAR INCINERATORS
In a survey to determine the currently available modular incinerators
that would represent state-of-the-art technologies and designs and various
configurations, the manufacturers' brochures were reviewed, and conversations
were held with manufacturer representatives to supplement the information in
the sales literature. Most of the manufacturers have several incinerator and
heat recovery models with capacities ranging from 15.4 to 90.7 Mg (17 to
100 tons) per day. Table 1 presents pertinent information about the differ-
ent systems, and Table 2 lists the manufacturers' addresses and telephone
numbers.
After analyzing the survey results, the incinerator systems were grouped
under five categories:
(1) Two horizontal cylindrical chambers with one above the other,
as manufactured by Environmental Control Products, Comtro, Morse
Boulger, Econo-therm, Kelley, Consumat, and Smokatrol (see Figure 2).
(2) Two horizontal rectangular chambers with one above the other, as
manufactured by Washburn & Granger, Basic, and Simonds (see
Figure 3).
(3) Two vertical cylindrical chambers with one above the other, as
manufactured by Burn-Zol and Lamb-Cargate (see Figures 4 and 5).
(4) A rotary primary chamber or a fixed primary chamber with a rotary
grate or auger and a fixed secondary chamber, as manufactured by
Scientific Energy Engineering, Giery, and C. E. Bartlett (see
Figures 6, 7, and 8).
(5) Two horizontal rectangular chambers with one after the other, as
manufactured by Clear Air (see Figure 9).
11
-------
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12
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TABLE 2. ADDRESSES AND TELEPHONE NUMBERS OF MODULAR
INCINERATOR MANUFACTURERS
Basic Environmental Engineering, Inc.
21W161 Hill
Glen Ellyn, Illinois 60137
(312) 469-5340
Burn-Zol
P.O. Box 109
Dover, New Jersey 07801
(201) 361-5900
C. E. Bartlett-Snow
200 West Monroe
Chicago, Illinois 60606
(312) 236-4044
Clear Air, Inc.
P.O. Box 111
Ogden, Utah 84402
(801) 399-9828
Comtro Division
180 Mercer Street
Meadville, Pennsylvania 16335
(814) 724-1456
Consumat
P.O. Box 9574
Richmond, Virginia
(804) 746-4120
23228
Econo-Therm
1132 K-Tel Drive
Minnetonka, Minnesota
(612) 938-3100
55343
Environmental Control Products
P.O. Box 15753
Charlotte, North Carolina 28210
(704) 588-1620
Environmental Services Corporation
P.O. Box 765
Crossville, Tennessee 38555
(615) 484-7673
Giery Company, Inc.
P.O. Box 17335
Milwaukee, Wisconsin
(414) 351-0740
53217
Kelley Company, Inc.
6720 N. Teutonia Avenue
Milwaukee, Wisconsin 53209
(414) 352-1000
Lamb-Cargate
P.O. Box 440
1135 Queens Avenue
New Westminster, British Columbia
V3L 4Y7 (604) 521-8821
Morse-Boulger
53-09 97th Place
Corona, New York
(212) 699-5000
11368
Scientific Energy Engineering, Inc.
1103 Blackstone Building
Jacksonville, Florida 32202
(904) 632-2102
Simonds Company
P.O. Drawer 32
Winter Haven, Florida 33880
(813) 293-2171
U.S. Smelting Furnace Company
(Smokatrol)
P.O. Box 217
Belleville, Illinois 62222
(618) 233-0129
Washburn and Granger
85 5th Avenue
Patterson, New Jersey
(201) 274-2522
13
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-SPARK ARRESTOR
-BLOWER
FIRE DOOR -
LOADING HOPPER
SECONDARY CHAMBER
PRIMARY CHAMBER
BURNER
— BURNER
-- ACCESS DOOR
- RESIDUE CHUTE
BLOWER
Figure 2. Configuration of two horizontal cylindrical
chambers with one above the other.
BURNER -
ACCESS DOOR -
- SPARK ARRESTOR
T
BLOWER
SECONDARY CHAMBER
PRIMARY CHAMBER
^BURNERS'
- FIRE DOOR
LOADER
BLOWER
Figure 3.
Configuration of two horizontal rectangular chambers
with one above the other.
14
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BLOWER-
BURNER
-a:
BLOWER —
T
a
SB
c
F
C
ERTIARY
HAMBER
I
SONDARY
HAMBER
I
RIMARY
HAMBER f
0
t.
r-i
r
t
LOADER
[ " 1
ll ii
ACCESS DOOR
Figure 4. Configuration of Burn-Zol's two vertical cylindrical
chambers with one above the other.
15
-------
Figure 5. Configuration of Lamb-Cargate's two vertical cylindrical
chambers with one above the other.
16
-------
SHREDDER/AIR CLASSIFIER
STEAM GENERATING SYSTEM/SE E INCINERATOR
AIR POLLUTION CONTROL
Figure 6. Configuration of Scientific Energy Engineering's
incinerator with an auger in the primary chamber.
HOPPER
GATES
REFUSE CHUTE -
GATES
IGNITION BURNER
FLUE GAS OUTLET
TO SCRUBBER
ROTARY BASKET
GRATE
RESIDUE
Figure 7. Configuration of Giery's incinerator with a rotary
grate in the primary chamber.
17
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BURNER
ROTARY PRIMARY
CHAMBER
LOADING L. V"*' /
RAM N f
fT If'-OiVo
LJ ^-v_jc'_>''
Figure 8.
RESIDUE PIT
Configuration of C. E. Bartlett's incinerator with a
rotary primary chamber.
ELECTROSTATIC
PRECIPITATOR
PRIMARY CHAMBER
WITH MOVING GRATE
WATER TUBE BOILER
Figure 9.
Configuration of Clear Air's incinerator-heat recovery
system with two horizontal rectangular chambers aligned
one after the other.
18
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SECTION 3
OVERVIEW OF FACILITIES AND THEIR EVALUATIONS
EVALUATION OVERVIEW
The current program was designed to evaluate small modular incinerators
in terms of operational data that would reflect the state-of-the-art of their
technologies. Since incinerators burning municipal solid waste have different
operating conditions than those burning industrial waste, a unit of each type
was separately evaluated. Although the two evaluations are documented
together, they are not compared since each typifies a discrete set of condi-
tions. Consequently, the reader is cautioned against drawing any comparative
conclusions.
The two selected facilities were each tested over three 1-week periods
to gather data for technical, environmental, and economic evaluations. The
technical evaluation consisted of (1) refuse and residue analyses, (2) effi-
ciency analyses of the incinerator and the heat recovery boiler, (3) an
operational data summary, and (4) a maintenance data summary. For each
facility, a mass balance was prepared for the weekly field test with the most
continuous and stable operating conditions to verify the accuracy of the data
used in the energy efficiency and balance calculations. In the mass balance,
the mass inputs to the system were calculated and compared with the measured
mass outputs from the system. In the energy balance, the measured input
energies were compared with the measured output energies. While the input
and output values in each of these balances should be equal, values close to
equality, i.e., less than a 5 percent difference between them, are normally
considered the best achievable.
The environmental evaluation consisted of analyses of the stack flue
gases, the residue, the process water, and the general plant environment. In
addition, an EPA Level 1 type of anlysis was designed to identify the organic
and inorganic elements in the system emissions. The EPA-recommended analysis
methods and sampling techniques were applied to investigate the emissions that
had a high potential for adversely affecting the environment. The economic
evaluation consisted of capital cost, actual operational cost, and projected
operational cost summaries.
NORTH LITTLE ROCK FACILITY
Description
The North Little Rock facility (referred to as the North Shore Energy
Plant) is located in an industrial area of North Little Rock, Arkansas (see
19
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Figure 10). During the time of this evaluation, the City was collecting, on
the average, 63.4 Mg (70 tons) of solid waste per day. The estimated 1978
waste throughput of the North Shore Plant was 13,721 Mg (15,125 tons). Four
Consumat Modular Model CS-1200 incinerators integrated with heat recovery
equipment burn the waste and produce steam which is delivered under contract
to the nearby Koppers Corporation, a manufacturer of creosote-treated wood
products. The contract calls for an average 6804 kg (15,000 Ib) per hour of
steam at 150 psi to be delivered 24 hours per day, 5 days per week.
NORTH LITTLE
ROCK
Figure 10. Vicinity map of North Little Rock facility.
The plant lies on a relatively flat, 8092-m2 (2-acre) site adjacent to
the Koppers plant. There are two structures on the site: a main building
with a wing on each side, one facing east and the other west, and an adminis-
tration building southwest of the main building and nearer to the plant
access (see Figure 11).
The central part of the main building is the tipping floor, and each of
the two wings contains an identical waste-to-heat energy module. Each
module consists of (1) a dual loading ram; (2) a display panel for refuse
loading instructions; (3) two control systems; (4) two identical incinerator
systems each including a primary chamber with an automatic residue removal
20
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SETTLING
POND
TIPPWG FLOOR BLHLDtNG
0
OFFICE
BLDG
Figure 11. Plant layout of North Little Rock facility.
system and a secondary chamber; (5) a tee section with a dump stack common to
the two incinerator systems; and (6) a heat recovery system that is common to
both systems including a water tube boiler, a soot blower, a water treatment
system, an aspirator section, and an exhaust stack (see Figure 12). Figure 13
shows the cross section of the system. The flow diagram of the process is
shown in Figure 14.
Operation
Refuse Loading—
The operator of the skid-steer tractor on the tipping floor has the
twofold task of pushing the truck-deposited refuse into each of the four
floor corners for temporary storage and of pushing the piled waste along the
loading platform to the hopper in both the east and the west waste-to-energy
modules.
The load-size indicators on the loading display panel are automatically
lighted according to the correlation of the primary chamber temperature with
preset lower and upper limits. The three load sizes, namely, LOAD HEAVY,
LOAD MEDIUM, and LOAD LIGHT, refer only to the quantity, that is, cubic
21
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22
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TO
HEAT
RECOVEf
BOILER
Y
1 1 T^~
\ \ SECONDARY CHAMBER
Figure 13. Cross section of incinerator module in North Little Rock facility,
yards of the refuse. Therefore, there is no need to vary the quality of
the refuse gathered for any one of the three load sizes indicated. When the
chamber temperature is above the high set point, the LOAD HEAVY frame, which
represents the largest load, illuminates so that the next load will lower
the temperature below the maximum level. When the chamber temperature is
at the desired operating level, the LOAD MEDIUM frame, which represents the
intermediate load, illuminates so that the next load will maintain the
current temperature. When the chamber temperature is below the low set point,
the LOAD LIGHT frame, which represents the smallest load, illuminates so
that the next load will raise the temperature above the minimum level.
Steam Production—
The gases are slowly drawn through the heat exchanger by a negative
pressure generated at the inlet side by the aspirator fan.
During steam production the cap at the base of the dump stack is
pneumatically closed. Since the cap is normally held open by a counterweight
as a fail-safe design, the flue gases are automatically discharged through
the dump stack whenever the power fails, the flue gas control system malfunc-
tions, the water in the steam drum or deaerator tank drops too low, or the
steam generation rate exceeds the steam demand rate.
23
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Flue Gas To
Atmosphe re
Condensate
Koppers ^ Return
Water
From ?
Solids To Water To
Landfill Drainage
Ditch
Water To
Dra mage
D 11 ch
Solids To
Landfill
Solid Waste
Figure 14. Flow diagram of incineration-heat recovery processes in
North Little Rock facility.
Residue Transfer and Removal—
The two rams on the hearth of the primary chamber are cycled to push
the residue forward and to break up clinker formations.
The residue removal ram is automatically cycled after several loading
cycles. As the residue falls into the wet sump, it is sprayed with water.
After a delay period the drag chain lifts the residue from the sump and
deposits it into the residue removal container.
Introduction to Test Program
The purpose of the testing was to provide detailed data on the facility
performance. Since both wings of the plant are identical and operate under
the same conditions, only one set of incinerators and the common steam
module were tested. The system in the west wing was chosen.
The facility was tested for 1-week periods during the months of March,
May, and October 1978. Of the three tests, the October test had the most
24
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continuous and stable operating conditions. The data for this test, there-
fore, were used in the technical evaluation of the facility.
The October test began at normal start-up Sunday night and lasted for
118.5 hours to late Friday night when burndown began. During that period,
204,300 kg (450,000 Ib) of refuse were burned at an average weekly rate of
1725 kg/hr (3800 Ib/hr) and at a daily rate ranging from 1634 to 1770 kg/hr
(3600 to 3900 Ib/hr) in the two incinerators being monitored.
Technical Evaluation
As indicated by Table 3, which summarizes the refuse weights and sorts
in 11 categories, the incinerator handled a wide variety of refuse sizes and
components. However, the operator manually removed large, bulky, explosive,
metallic, and wire objects before the refuse was dumped into the loading
hopper.
During the three field tests, the refuse had a moisture content varying
from 22 to 35 percent and an average bulk density of 97.7 kg/m3 (165 lb/yd3).
The residue had an average bulk density of 896 kg/m3 (1510 lb/yd3) with
69 percent of the residue particles being smaller than 1 inch. The refuse
reduction through combustion was 55 percent by weight and 95 percent by
volume based on the ratio of wet residue to as-received refuse. On a dry
residue basis, the refuse weight reduction was 70 percent.
The weekly system mass balance for the October field test compares the
mass flows entering and leaving the incinerator-heat recovery system. While
the system inputs measured were the refuse, the combustion air, the auxiliary
gas, the residue cooling water, and the aspirator fan air, the system outputs
measured were the residue and the boiler exhaust stack flue gas. Figure 15
presents the mass balance on a per ton input basis. Over the 118.5-hour test,
the total mass input was 4127 Mg (4550 tons) and the mass output was 4199 Mg
(4629 tons). The difference, namely 71.7 Mg (79 tons) or 2 percent of the
output, was not accounted for.
The energy balance in Figure 16 compares the measured energy inputs and
outputs on a per ton input basis. For this balance, the inputs were refuse,
electricity, and auxiliary fuel while the outputs were steam, sensible heat
and remaining energy in the residue, heat lost by radiation and convection,
and sensible heat in the flue gases. The energy inputs and outputs on the
118.5-hour test totaled 2298 and 2350 GJ (2178 and 2228 MBTU), respectively.
The lesser energy output of 52 GJ (50 MBtu) or 2 percent of the energy input,
was well within the expected +5 percent closure.
Each of the two Gonsumat heat recovery modules was designed to produce
4,540 kg (10,000 Ib) of steam per hour. The total plant steam demand, as
measured by a Honeywell steam flow integrator, averaged 4,994 kg (11,000 Ib)
per hour with a maximum and minimum of 6,356 and 2,724 kg (14,000 and
6,000 Ib) per hour. On the average, the plant steam demand was 79 percent of
the original anticipated demand of 6,810 kg (15,000 Ib) per hour. The west-
end waste-to-energy module (the module tested) had steam ouputs that averaged
3,746 kg (8,250 Ib) per hour and reached levels between 4,994 and 5,357 kg
(11,000 and 11,800 Ib) per hour during peak demand periods that lasted from
25
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Table 3. NORTH LITTLE ROCK WEEKLY REFUSE COMPOSITION FOR MARCH, MAY,
AND OCTOBER TESTS
Test Period
Category
Food waste
Garden
Paper
Plastic
Textiles
Wood
Ferrous
Aluminum
Glass
Inert
Fines
Weekly %
by weight
8.8
7.2
48.1
6.1
3.4
1.4
8.3
1.1
10.9
1.6
3.2
March
Category weight
kg(lb)
13,104( 28,890)
10,722( 23,638)
71,692(157,914)
9,084( 20,027)
5,063( 11,162)
2,085( 4,596)
12,360( 27,249)
1,638( 3,611)
16,232( 35,785)
2,383( 5,253)
4,765( 10,506)
Weekly %
by weight
6.7
4.2
49.6
7.4
1.5
1.1
9.8
1.8
11.8
0.4
5.7
May
Category weight
kg(lb)
10,332( 22,779)
6,477( 14,279)
76,489(168,630)
11,412( 25,159)
2,313( 5,100)
1,696( 3,740)
15,113( 33,318)
2,776( 6,120)
18,197( 40,118)
617( 1,360)
8,791( 19,380)
Weekly %
by weight
6.8
3.0
54.1
8.7
2.2
1.0
8.8
3.2
7.6
0.3
4.1
October
Category weight
kg(lb)
13,880( 30,600)
6,123( 13,500)
110,019(242,550)
17,758( 39,150)
4,491( 9,900)
2,041( 4,500)
17,962( 39,600)
6,532( 14,400)
15,513( 34,200)
612( 1,350)
8,369( 18,450)
Total//
100.1
149,198(328,631)
100.0 154,350(339,980)
99.f
203,483(448,200)
# Totals do not equal weighed refuse total due to rounding and averaging.
30 to 60 minutes. The pressure in the steam drum varied from 120 psi at peak
demands, to 130 psi at the average steam demand, and to a high of 140 psi at
the low steam demand. The efficiency of the refuse combustion was 94 percent,
or 6 percent of the combustibles were unburned and removed with the residue.
The system energy efficiencies, as calculated by the input-output, and the
heat loss methods were 56 and 54 percent, respectively. Because of the high
moisture and hydrogen content of the refuse, the net efficiency of the system
was calculated with a net heating value to eliminate the heat lost by evapo-
rating the moisture. The resultant 65 percent efficiency was 9 to 11 percent
higher than the efficiency computed with the total or as-received heating
value.
The operation of the facility required a total of nine personnel, i.e.,
one supervisor, one office manager, one truck driver, and two operators per
shift for each of the three shifts. The supervisor position was critical to
the successful operation of the plant. The office manager maintained all
plant records such as those for utilities, refuse delivery, and steam con-
sumption. The truck driver transported the residue to the disposal site.
26
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Mass balance 118.5-hour test*
Input
Output
Mg per Mg refuse "/, of Total Mg per Mg refuse % of Total
Ton per ton refuse
Ton per ton refuse
Refuse
Natural gas
Residue,
cooling water 0.157
Aspirator air 10.26
Blower air 8.88
Residue, wet
Flue gases
Total
20.299
4.92
0.01
0.77
50.54
43.76
100.00
0.45
20.13
20.58
2.19
97.81
100.00
* Total refuse input 204 Mg (225 tons)
BOILER STACK
FLUE GAS
BLOWER
REFUSE
-ASPIRATOR
.—RESIDUE-
Figure 15. Mass balance for incineration-heat recovery processes in
North Little Rock facility during the 118.5-hour October
field test.
27
-------
Knergv balan
118 . 5-hour tres t
Source
GJ per I MBtu per
Mg of refuse Won of refuse
of total
C, I per
Mg of re I us
Output
MBtu per
Ton of refuse
Refuse
Electricity
Natural gas
Unburned
combustibles
Steam
Flue gases
Radiation and
Convection
Total
11.12
.09
.052
0. ~>b
11.51
*Total refuse input 204 Mg (225 ton)
BOILER STACK
FLUE GAS
DUMP STACK
FLUE GAS
JL
t
R/C LOSSES
BOILER
GAS-
-STEAM-
ELECTRICITY-
REFUSE-
PRIMARY
UNBURNED
COMBUSTIBLES
of total
Figure 16. Energy balance for incineration-heat recovery processes in
North Little Rock facility during the 118.5-hour October
field test.
The two operators shared routine maintenance and incinerator loading opera-
tions. The steady-state, efficient operation of the system requires that the
operators closely follow the start-up procedures, the automatic loading
instructions, and the burndown procedures. The effects on the system temper-
atures and gaseous emissions when the hopper loads varied from light to
heavy are shown in Figures 17 and 18.
28
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LEGEND
(5Temperature in Primary Chamber No. 3.
@i Temperature in Secondary Chamber No. 3.
@. Temperature in Primary Chamber No. 4.
© Temperature in Secondary Chamber No. 4.
©• Temnerature at Boiler Entrance.
EVENTS
1. Load, light No. 4 6. Load, medium No.
2. Load, light No. 3 7. Load, light No.
3. Load, medium No. 4 8. Load, medium No.
4. Residue, dump No. 4 9. Load, medium No.
5. Load, light No. 3 10. Load, medium No.
Figure 17. System temperature versus loading sizes and events in North
Little Rock facility.
29
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tack Orsat
CO, 4 3.7%
-4
I
! Perijod of i
^Aspirator
! Off)
Clean Lena
X10 = ppm
X 5 = ppm
Pejriod of
Heajvy Loads
;3. Opacity = percent
4. CO2 ORSAT
5. 02 T 4 = percent
: I
Figure 18. Stack emission during heavy and light loading periods in
North Little Rock facility.
The routine maintenance of the facility required a working knowledge
of the hydraulic, electronic, and mechanical systems. A supply of small
spare parts, such as switches, thermocouples, hydraulic parts, and motors,
was essential for continuous 24-hour operation. While major maintenance
during the week required shutting down the incinerator, much maintenance
could be performed during an hour or two with the incinerator still operating
but at reduced capacity. Normally, the major maintenance (if required) and
removal of soot deposits in the boiler were performed during the weekend.
30
-------
Environmental Evaluation
For the October test, Table 4 presents the flue gas emissions in terms
of grains per standard cubic foot (gr/SCF) and grams per standard cubic meter
(g/SCM) and pounds per ton of refuse processed. Table 5 summarizes the
emissions for each of the three test periods. The size distribution analysis
of the particulates during the October test revealed that 95 percent by
weight of the particulates were smaller than 7 ym and 50 percent by weight
were 0.3 ym or less. In five October tests for total particulates, including
the wet-catch particulates, the total particulates, corrected to 12 percent
C02 averaged 0.397 g/SCM (0.174 gr/DSCF) with a maximum of 0.500 g/SCM
(0.219 gr/DSCF) and with a minimum of .271 g/SCM (0.119 gr/DSCF). While the
concentrations of chloride ranged from 19 to 610 mg/m3 (13 to 420 ppm) and
averaged 187 mg/m3 (130 ppm), those of fluoride ranged from 0.5 to 4.3 mg/m
(0.6 to 5.5 ppm) and averaged 1.6 mg/m3 (2.0 ppm) over the three test periods.
TABLE 4. NORTH LITTLE ROCK POLLUTANT EMISSION RATES
FOR OCTOBER TEST
Pollutant
Particulate
SOX
NOX
CO
HC
Pb
Emission rate
Ib/ton refuse
Maximum Average Minimum charged"!"
.231* gr/SCF .130* gr/SCF .067* gr/SCF
<10 ppm
99 ppm 82 ppm 69 ppm
36 ppm 29 ppm 16 ppm
40 ppm 28 ppm 20 ppm
4.49 mg/m3
3.03
<0.78
3.68
1.00
0.55
0.14
* Corrected to 12 percent C02.
t Based on an average flow of 15,198 DSCFM including aspirator air and a
feed rate of 1.9 TPH.
31
-------
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32
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The mechanical functions and the operational procedures were investigated
to determine their effect on the particulate emission level. Within the scope
of the available data, the emission level increased whenever the temperature
in the primary chamber, the size of the charging load, or the amount of under-
fired air increased. The individual effects of these parameters could not be
determined because of their interrelationships in the system. The particulate
emission level could not be correlated with the following: excess air amounts,
secondary chamber temperature, residue ram action, aspirator fan flow rate,
and the waste characteristics.
The plant was designed to meet a state-imposed particulate standard
of 0.2 gr/DSCF corrected to 12 percent C02. The present federal standard
for municipal incinerators with capacities greater than 50 TPD is 0.08 gr/DSCF
corrected to 12 percent C02. However, this standard does not apply to
the North Little Rock facility because each pair of incinerator units is
rated at less than 50 TPD. Since the facility complied with the emissions
limitation prescribed in its permit, the reader is cautioned against
assuming that the North Little Rock facility did not comply with the
federal standard.
A similar unit in Salem, Virginia, was designed to meet a state-
imposed standard of 0.08 gr/DSCF corrected to 12 percent C02- As of the
date of this publication (September 1979), this small modular system
(with automatic feed and ash removal) has not demonstrated its capability
of meeting the state air emission standards.
The daily discharge of process water varied from 37.85 to 113.5 m3
(10,000 to 30,000 gallons). Of the significant discharge water character-
istics, the tipping floor water had a BOD of 1780 mg/i, a COD of 2710 mg/£,
and an arsenic level of 9 mg/Ji; and the residue removal sump water had a
pH of 12 and a temperature of 39° C. The tipping .floor water is treated by a
municipal treatment plant. Concentrations of the pollutants are not high
enough to affect the treatment plant's operation.
The residue contained unburned hydrocarbons and traces of a wide range
of heavy metals. The tests on the laboratory-produced leachate, as sum-
marized in Table 6, revealed insignificant amounts of pollutants. This
finding was due primarily to high pH levels that restricted the solubility of
the heavy metals in the leachate. Although the laboratory-tested residue and
leachate had insignificant amounts of pollutants, the residue could be a
source of pollution if its pH level dropped enough to allow the solubility
of the residue heavy metals during the surface drainage at the local site
and/or the leachate formation at the disposal site.
Within the facility building, the levels and the viable microorganism
content of the fugitive dust were low, and the noise levels never exceeded
the OSHA limits (see Figure 19).
Outside the building no significant amounts of pollutants were found at
the upwind or downwind ambient air sample sites; both sites were at a
91.4-meter (300-foot) distance from the. boiler exhaust stack. The noise
levels were within standard limits (see Figure 20).
33
-------
TABLE 6. NORTH LITTLE ROCK RESIDUE LEACHATE PARAMETER
AND COMPONENT VALUES
pH
Conductivity
Alkalinity
TKN
Hardness
TOC
Ortho-Phosphate
Total Phosphate
Sulfide
Chloride
Acidity
Total Dissolved
Solids
Ammonia as N
COD
Sulfate
Bromide
Fluoride
Boron
Mercury
Cadmium
Antimony
Lead
Chromium
Arsenic
Cyanide
Phenols
MBAS
Sulfur
umhos
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
mg/1
Tag /I
Mg/1
Mg/1
Mg/1
Mg/1
MG/1
Mg/1
mg/1
mg/1
mg/1
mg/1
Water Blank
5.52
2.78
1.10
6.95
2.00
3.10
0.005
0.01
<0.002
ND
5
<1
0.216
ND
<1.00
<0.100
0.058
<0.1
<0.1
<1
<1.0
<1
<1
ND
-
-
-
=, = =
Test 1
8.65
185.00
43.50
5.25
70.00
5.70
0.025
0.044
0.002
0.71
ND
80
0.183
ND
34.30
<0.100
0.099
<0. 1
<0.1
<1
5.4
<1
<1
ND
_
_
-
Phosphate
Test
6.05
2800
144
11.6
ND
2.2
1400
1975
ND
12
1841
5770
0.23
ND
16.6
1.0
.07
.127
_
_
_
_
_
< .002
.005
0.12
ND = None detected
34
-------
INCINERATOR
Near Compressor on(off)
Soot Blower on(off)
Boiler
Hydraulic Loader on(off)
Storage Area
Near Electrical Panel
Loading Area
W/Skid-Steer Lpader
Near Residue Conveyor
84 -
88(84)
88(87)
82
88(81)
84
83
82
88
79
105
100
94
93
&
CONVEYOR
Figure 19. In-plant noise-level plot for North Little Rock facility.
35
-------
SAMPLE LOCATION
TO) dBA LEVEL
Figure 20. Outside-plant noise-level plot for North Little Rock facility.
36
-------
The major elements detected in the EPA Level 1 analysis are shown in
Table 7. Other metals and elements were found occasionally in smaller
amount s.
TABLE 7. NORTH LITTLE ROCK SUMMARY OF ELEMENTS
DETECTED IN STACK EMISSION FILTERS
Element
Silicon
Iron
Aluminum
Sodium
Calcium
Potassium
Magnesium
Lead
Zinc
Cadmium
Beryllium
Titanium
Chromium
Copper
Nickel
Manganese
Lithium
Antimony
Boron
Tin
Vanadium
Emission rate
Concentration in gas
(yg/m3)*
3.22
261.
331.
9,363.
894.
381.
331.
4,280.
9,071.
123.
0.114
.333
1.105
62.57
1.97
8.02
2.48
13.26
105.0
3.81
2.26
Emission factor
g/Mg of refuser
.0505
4.10
5.20
147.0
14.0
5.98
5.20
67.2
142.
1.93
.0018
.0052
.0173
.982
.031
.126
.039
.208
1.640
.0598
.0354
* Concentrations based on a composite of six filters from
October test period.
t g/Mg * 500 = Ib/ton
37
-------
Economic Evaluation
The total cost of the plant in 1977 was $1,529,404. Table 8 presents
the total capital cost breakdown by EPA cost categories, and Table 9 presents
the unit operational cost. These costs are based on averages of the actual
unit costs over the evaluation period. Table 10 presents the projected
annual operating and maintenance costs based on the as-operating parameters;
i.e., feed rate and steam capacity equal to 2.72 Mg (3 tons) and 7274 kg
(16,000 Ib) per hour, respectively.
Table 11 presents the estimated annual revenues. The as-operated
economic and production conditions yield a total revenue and a revenue
per Mg of refuse processed that are respectively $177,335 and $10.94.
TABLE 8. NORTH LITTLE ROCK ACTUAL CAPITAL COSTS*
Land
Site preparation
Design
Construction
Real equipment
Other equipment
Other costs
$ 10,000
101,093
37,583
311,383
968,929
62,886
37,530
Total capital investment $1,529,404
*Based on actual costs in 1977.
38
-------
TABLE 9. NORTH LITTLE ROCK UNIT COST DATA*
Annual salary rates:
Director of sanitation $19,000
Plant superintendent 13,290
Maintenance superintendent 10,800
Operator 9,442
Truck driver 8,086
Secretary 7,956
Overtime 5,000
Employee benefits:
Health insurance (each employee) $29.70/month
Retirement 5.00%
FICA 6.05%
Fuel rates:
Natural gas $0.056/1000 I
Number 2 diesel oil $0.122/£
Gasoline $0.140/£
Electricity: $0.034/kwh
Water and sewer: $0.0918/1000 I
*Based on cost projections from costs incurred during
September 1978.
39
-------
TABLE 10. NORTH LITTLE ROCK PROJECTED ANNUAL
OPERATING AND MAINTENANCE COSTS-
Cost
Item
Salaries
Employee benefits
fuel - no. 2 diesel
Natural gas
Gasoline
Electricity
Water and sewer
Maintenance
($/yr)
$111,284
15,750
3,456
16,704
2,916
19,237
6,402
65,656
($/Mg)
$ 6.87
0.97
0.21
1.03
0.18
1.19
0.40
4.05
Replacement equipment
Residue removal
Chemicals
Interest
Depreciation
Other overhead
Total operating and
maintenance costs
t t
3,400 0.21
39,179 2.42
78,070 4.82
3,209 0.20
$365,263
$22.55
* Based on costs incurred during September 1978.
i Cost included in salaries and employee benefit categories.
40
-------
TABLE 11. NORTH LITTLE ROCK PROJECTED
ANNUAL REVENUES*
Sources Revenue
Steam production $152,999
Commercial dumping fees 24,336
Total $177,335
Per Mg of refuse processed (per ton) $10.94 (9.92)
* Based on 1978 dollars.
With $365,263 as the projected annual operating and maintenance cost
and $177,335 as the estimated annual revenue, the net annual operating cost
will be $187,928. Table 12 presents the costs, revenues, and net costs per
unit of refuse processed.
In summary, with the facility requiring an initial capital investment of
$1,529,404 in 1977, its anticipated annual operation in 1978 dollars will cost
$187,928 or $11.67 per Mg ($10.53 per ton) of refuse processed.
TABLE 12. NORTH LITTLE ROCK PROJECTED ANNUAL
NET OPERATING COSTS*
Cost
($/Mg) ($/ton)
Operating and maintenance costs 22.55 20.45
Revenue 10.94 9.92
Net cost of operation 11.67 10.53
(tipping fee)
* Based on costs incurred during September 1978.
41
-------
MARYSVILLE FACILITY
Description
This facility is located at the Truck Axle Division of the Rockwell
International Corporation in Marysville, Ohio (see Figure 21). The system
was intended for the twofold purpose of burning the division's solid waste,
mostly packing and shipping scraps, and of providing energy for both heating
and cooling the main building by recovering the combustion gas heat in the
form of hot water.
SITE LOCATION
ROCKWELL
INTERNATIONAL
Figure 21. Vicinity map of Marysville (Rockwell International) vacility.
42
-------
The waste-to-heat system includes a Kelley Model 1280 incinerator with a
Kelley Model 72 feeder and a York-Shipley Series 565 firetube boiler.
Figures 22 and 23 show a functional schematic of the entire system and a
three-dimensional, cutaway drawing of the incinerator module, respectively.
Both the primary and secondary chambers of the incinerator are outside the
facility housing so that the main building is remote from excessive heat
radiating from the incinerator (see Figure 24).
While the refuse is burned 16 hours a day 5 days per week throughout the
year, the hot water is generated only as needed to maintain the prescribed
temperatures.
EXHAUST STACK
HOT WATER TO
HEATING SYSTEM
ASH
REMOVAL DOOR
Figure 22. Functional schematic of incineration-heat recovery processes
in Marysville facility.
43
-------
Main chamber burntr
Air manifold
Figure 23. Three-dimensional, cutaway drawing of incinerator module
in Marysville facility.
44
-------
WAREHOUSE
ASSEMBLY PLANT
GUARD HOUSE
OFFICE
VISITOR PARKING
B
CT
S
A
L
C
PC
TR
BOILER
COOLING TOWER
STACK
ASH CONTAINER
LOADER
CHILLING UNIT
PRIMARY CHAMBER
THERMAL REACTOR
MARYSVILLE
Figure 24. Plant layout of Marysville facility.
45
-------
The incinerator system includes a loading hopper and ram module, a
pyrolytic primary chamber with an automatic residue removal system, a
secondary chamber, a hot water boiler system, and an exhaust gas stack. The
process flow diagram is shown in Figure 25.
Flue CJK
To Atmosphere
Heating/Cool ing
System
Municipal
Water
Solid Waste
Figure 25. Flow diagram of incineration-heat recovery processes in
Marysville facility.
46
-------
Operation
Refuse Loading—
A fork lift vehicle transports the packing and shipping scraps and other
solid waste in small containers to the refuse hopper. When the hopper door is
opened, the vehicle operator lifts the containers and dumps the refuse into
the hopper. Then the operator depresses the START button on the control
panel to activate an automatic loading sequence.
Chamber Operations—
Manufacturer performance specifications indicate that the primary, or
pyrolysis, chamber operates at 30 percent of the air required for stoichio-
metric combustion. The secondary chamber, or thermal reactor, operates at a
maximum of 150 percent of stoichiometric air.
Introduction to Test Program
The facility was tested for 1-week periods during the months of April,
July, and August 1978. The system was tested during the heat recovery period
of the daily operation. Since the unit was used for heating and cooling of
the plant, there was frequent cycling from energy to non-energy recovery
during mild weather periods. Of these three tests, the July test had the
most continuous and stable operating conditions. The data for this test,
therefore, were used in the technical evaluation of the facility. The July
test lasted for 120 hours. Energy was recovered during 75.5 hours of the
80 hours of operation, and the five daily burndown cycles totaled 40 hours.
During the July test the incinerator operated at 63 percent of capacity. A
total of 25,652 kg (56,552 Ib) of wood and paper waste was burned at an
hourly average of 340 kg (750 Ib).
Technical Evaluation
During the three field tests, the refuse had a moisture content that
ranged from 7 to 11 percent with an average of 9.3 percent. Of the 51,722 kg
(114,027 Ib) of refuse burned, as shown in Table 13, 65.7 percent was wood;
33.8 percent was paper; and the remaining 0.5 percent was plastics, paint,
inerts, textiles, and rubber. On the average, the measured energy values of
the wood and paper were 18.04 and 17.89 MJ/kg (7758 and 7693 Btu/lb), respec-
tively. The residue had an average bulk density of 428 kg/m3 (726 lb/yd3)
with 97 percent being inerts and the remaining 3 percent being combustibles.
The refuse reduction through combustion was 95 percent by weight.
The weekly system mass balance for the July field test compares the mass
flow entering and leaving the incinerator-heat recovery system. The system
inputs were the refuse, the combustion fan air, the auxiliary gas, the quench
water, and the afterburner air. The system outputs were the residue, hot
water, and the boiler exhaust flue gas. The mass balance shown in Figure 26
covers two time periods: one for 75.35 hours while the system was in full
heat recovery operation and the other for 44.62 hours while the system was in
burndown cycles. Excluding the combustion air, the measured inputs totaled
42.6 Mg (47 tons). The air input could not be measured and had to be com-
puted by the difference method.
47
-------
TABLE 13. MARYSVILLE WEEKLY REFUSE COMPOSITION FOR APRIL, JULY,
AND AUGUST TESTS
Category April
kg (lb)
Total 13,151 (28,994)
Wood 7,324 (16,147
Paper 5,768 (12,717)
Plastics
Paint 59 (130)
Crease
Ini'rt
Textiles
Rubber
Test Period
July August
kg (lb) kg (lb)
25,652 (56,552) 12,919
18,684 (41,191) 7,985
6,940 (11,300) 4,782
17 (38) 14
12 (26) 20
82
13
22
(28,481)
(17,605)
(10,543)
(31)
(45)
(181)
(28)
(48)
Total Percent
kg (lb) of Total
51,722
33,993
17,490
31
59
32
83
13
22
(114,027)
(74,943)
(38,557)
(69)
(130)
(71)
(181)
(28)
(48)
65.7
33.8
<.l
<.l
.1
<.l
<.l
In the computation of the system mass balance on a per ton input basis,
shown in Figure 26, the amounts of the combustion air and the afterburner
section air had to be computed by subtracting the mass of the other inputs
from the total mass output. This was done because the air masses could not
be directly measured.
During the second field test, the energy recovered was 150 GJ (142 MBtu)
as measured by the BTU meter and 180 GJ (174 MBtu) as computed by the heat
loss method. The effectiveness and the thermal efficiency of the boiler were
90 and 82 percent, respectively.
48
-------
Mass balance 120-hour test*
Input
Output
Mg per Mg refuse'
Source or
Ton per ton refuse
% of Total
Mg per Mg refuse
or
i'on per ton refus
of Total
Refuse
Cooling spray
water
Natural gas
Combustion air
Flue gases
Residue, dry
Total
1.00
0.65
0.02
18.39
20.06
4.99
3.24
0.10
91.67
100.00
20.01
.04
99.80
0.20
100.00
* Total refuse input 25-b Mg (28.3 tons)
GAS
WATER
REFUSE
Figure 26. Mass balance for incineration-heat recovery processes in
Marysville faciltiy during the 120-hour (75.5-hour heat
recovery) July field test.
The energy balance in Figure 27 compares the measured energy inputs and
outputs on a per ton input basis. For this balance, the inputs were refuse,
quench water, auxiliary fuel, and electricity. The outputs were the hot
water generated, sensible heat and remaining energy in the residue, heat lost
by radiation and convection, and sensible heat in the flue gases. The energy
inputs and outputs for the 120-hour test totaled 436 GJ and 409 GJ (413 and
388 MBtu), respectively. The difference of 27 GJ (25 MBtu) or 6 percent
of the energy input was not accounted for.
As shown in Figure 27 for the energy balance, 19 percent of the heat
was lost by radiation and convection, and 14 percent was lost during the
burndown cycles.
49
-------
Ene rgy ba1ance 120-hour_test*_
Input
Output
GJ per I MBtu per \ 7. of total GJ per I KBtu per
Source Mg of refuse \Ton of refuse) Mg of refuse \ Ton of refuse
Refuse 16.36
Electricity 0.12
Natural gas
Heat recovery 0.29
Burndown 0.21
Residue
Radiation and
Convection
Heat recovery
Burndown
Flue gases
Heat recovery
Burndown
tHot water
(measured)
16.98
(14.07) 96.4
( 0.10) 0.7
( 0.25) 1.7
( 0.18) 1.2
0.
2 _
0.
4.
2 _
6.
(14.60) 100.0 15.
03
26
82
19
27
.09
.66
( .
(1,
(0.
(3,
(1.
(5
(13.
03)
,94)
.71)
,60)
.95)
.24)
.47)
j % of total
0.
14,
5
26,
14.
38
100,
2
,4
.3
,7
,5
.9
.0
*Total refuse input 25.6 Mg (28.3 ton)
tHot water output by difference 7.41 GJ/Mg refuse (6.37 MBtu/ton)
FLUE GAS
CAS
HOT WATER
Figure 27. Energy balance for incineration-heat recovery processes in
Marysville facility during the 120-hour (75.5-hour heat
recovery) July field test.
The system energy efficiency during the heat recovery periods as
calculated by the heat loss method was 54 percent. The system energy
efficiency for a week-long test, including heat recovery and burndown
periods was 42 percent. The net efficiencies were 54 and 43 percent,
respectively.
While the facility was capable of handling all incoming refuse and of
meeting the plant's heating and cooling demands, it operated at only 63 per-
cent of capacity during the two 8-hour shifts.
The delivery of waste varied widely in amounts and times. The unit was
underfed most of the time, but occasionally it was overfed. This is evidenced
50
-------
by Figure 28 which shows an overload period when the boiler entrance tempera-
ture was higher than the secondary chamber temperature. Figure 29 shows gas
emission peaks caused by overfeeding during the same period.
One man could readily operate the facility. Corrective maintenance
required (1) once or twice a week removal of residue, (2) the weekly removal
of particulate accumulations from the blades on the induced draft fan that
made the fan vibrate excessively toward the end of the week, and (3) the
semiannual removal of slag accumulations from the boiler tubes.
1. Primary Chamber Temperature
2. Secondary Chamber Temperature
3. Boiler Entrance Temperature
Figure 28. System temperatures during peak loading periods in
Marysville facility.
51
-------
x 5 = ppm
x 10 = ppm
x 5 = ppm
= percent
ent
2. CO
3. NOX
4. Opacity
Figure 29. Stack emissions during peak loading periods in Marysville facility.
52
-------
Environmental Evaluation
For the July test, Table 14 presents the flue gas emissions in terms
of grains or ppm and of pounds per hour per ton of refuse processed. Table 15
summarizes the emissions for each of the three test periods. The size distri-
bution analysis of the particulates during the July test revealed that
85 percent by weight of the particulates were smaller than 7 ym. The concen-
trations of chloride ranged from 4 to 136 mg/m3 (3 to 94 ppm) and averaged
38 mg/m3 (26 ppm) while those of fluoride ranged from 0.2 to 2.0 mg/m3
(0.3 to 2.6 ppm) and averaged 0.9 mg/m3 (1.1 ppm) over the. three test periods.
The light (Ci to C6) hydrocarbons varied widely in the range from 1.8 to
1423 mg/m3 (1.2 to 936 ppm).
No significant amounts of pollutants were found in the residue or its
laboratory-produced leachate (see Table 16). Within the facility building,
the fugitive dust levels were low, and no noise levels exceeded the OSHA
limits (see Figure 30). No significant amounts of pollutants were found at
the upwind or downwind ambient air sample sites which were both at a 91.4-m
(300-ft) distance from the boiler exhaust stack.
TABLE 14. MARYSVILLE POLLUTANT EMISSION RATES FOR JULY TEST
Emission rate
Pollutant
Particulate
SOX
NOX
CO
HC
Lead
Maximum Average
0.111 gr/SCF* .049 gr/SCF* .
31 ppm 8 ppm
125 ppm 30 ppm
<1000 ppm 240 ppm
2285 ppm 765 ppm
624 yg/m3
Ib/ton refuse
Minimum charged
033 gr/SCF* 2.01
<5 ppm .44
6 ppm 1.19
17 ppm 5.81
21 ppm 10.4
0.02
* Corrected to 12 percent C02.
53
-------
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-------
TABLE 16. MARYSVILLE RESIDUE LEACHATE PARAMETER AND
COMPONENT VALUES
Phosphate Buffer
Water Blank Test 1 Test 2
PH
Conductivity
Alkalinity
TKN
Hardness
TOC
Ortho-Phosphate
Total Phosphate
Sulfide
Chloride
Acidity
Total Dissolved
Solids
Ammonia as N
COD
Sulfate
Bromide
Fluoride
Boron
Mercury
Cadmium
Antimony
Lead
Chromium
Arsenic
MBAS
Phenols
Cyanide
umhos
mg/£
mg/8,
mg/£
mg/£
mg/J.
mg/£
mg/£
mg/S,
mg/£
mg/£
mg/£
mg/L
mg/>i
mg/£
mg/£
mg/£
Ug/1
t>g/£
Pg/«
v-g/s.
Vg/i
mg/J!
mg/fc
mg/5.
5.52
2.78
1.10
6.95
2.00
3.10
0.005
0.01
<0.002
ND
5
<1
0.216
ND
<1.00
<0.1uO
0.058
<0.1
<0.1
<1
<1.0
<1
<1
ND
-
-
—
10.24
379.00
78.10
2.59
112.30
5.00
0.002
0.063
<0.002
1.51
ND
236
0.170
ND
68.00
<0.100
0.662
2.6
<0.1
<1
18.7
1.3
3280
ND
-
-
~
6.2
3700
232
7.05
<0.1
<1
1230
1360
< .003
43
1938
6012
0.076
52.5
0.19
0.64
0.363
65.6
_
-
-
-
-
-
.121
.080
.002
ND = None detected
55
-------
PRIMARY CHAMBER
BUILDING
LOADER
BOILER
ID FAN
LOCATION
1 LOADER
2 LOADER
3 WORK FLOOR
4 BOILER FRONT
5 BOILER REAR
SOUND LEVEL, dB
77
78
78
83
83
6 ELECTRICAL PANELS 80
Figure 30. In-plant noise-level plot for Marysville facility.
Of the pollutants detected in the EPA Level 1 analysis, antimony,
arsenic, mercLiry, and heavy organic compounds were found consistently in
small amounts. Other metals such as lead, cadmium, chromium, and barium
were found occasionally in small amounts (see Table 17). The contaminants
ware found in the stack emissions and the residue.
Economic Evaluation
The total cost of the facility was $509,949 in 1977. Table 18 presents
the total cost breakdown by EPA cost categories, and Table 19 presents the
unit operational costs which were obtained from records maintained by the
plant engineer. Table 20 presents a comprehensive economic evaluation for
each cost center based on actual operating conditions during July.
56
-------
TABLE 17. MARYSVILLE SUMMARY OF ELEMENTS
DETECTED IN STACK EMISSION FILTERS
Emission rate
Element
Concentration in gas
(yg/m3)*
Emission factor
g/Mg of refuset
Silicon
Iron
Aluminum
Sodium
Calcium
Potassium
Magnesium
Lead
Zinc
Cadmium
Beryllium
Titanium
Chromium
Copper
Nickel
Manganese
Lithium
Antimony
Boron
Tin
Vanadium
2.95
520.
2,202.
13,839.
1,749.
450.
640.
624.
2,724.
428.
0.09
0.419
1.66
19.3
1.78
11.4
2.10
1.69
98.1
3.33
2.30
.042
7.45
31.5
198.0
25.0
6.44
9.17
8.93
39.0
6.14
.0014
.0060
.0237
.277
.0255
.164
.030
.0243
1.41
.0477
.033
* Concentrations based on a composite of five filters from
July test period.
t g/Mg T 500 = Ib/ton
TABLE 18. MARYSVILLE CAPITAL COSTS*
Incineration Heat Recovery
Land
Site preparation
Design
Construction
Real equipment
Total capital investment
$ 1,000
t
7,000
69,302
77,302
$ 2,000
t
12,500
82,166
335,081
432,647
* Based on 1977 dollars.
t Site preparation costs were not identified in Rockwell
International Corporation accounting records.
57
-------
TABLE 19. MARYSVILLE UNIT COST DATA*
Salary rates (annual, .FY 78):
General helper $14,500
Employee benefits rate $5,800
Natural gas $0.091/k£
Electricity rate $0.0282/kwh
Water rate $0.24/1000£
Sewer t
Chemical (NC-1) costs $2.30/£
*Based on costs incurred in 1978.
tOn-site disposal (septic system).
Although the incinerator-heat recovery facility was installed to
provide an assured energy supply for the plant's heating and air conditioning
systems, and not to produce revenue by itself, it indirectly produces a
revenue by eliminating the costs previously expended for the propane used
during the winter, for the electricity used during the summer, and for the
compactor and container used to dispose of the solid waste.
During the three test periods, the average heat recovery rate was
23,025 MJ (21.8 MBtu) per day. With estimated heating and cooling seasons
of 128 and 122 days, respectively, and with the previous propane and
electricity costs of $0.00404 and $0.00769 per MJ ($3.83 and $7.29 per
MBtu), respectively, the facility yielded an annual savings, or annual
revenue equivalent, of $23,557. The costs of the solid waste disposal
method that were replaced amounted to $27,500 per year or $24.21 per Mg
($22.95 per ton). The net operating costs by system function are shown in
Table 21.
58
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TABLE 20. MARYSVILLE PROJECTED ANNUAL OPERATING AND MAINTENANCE
COSTS PER COST CENTER*
Cost Center
Cost classification
Salaries
Employee benefits
Fuel
Water and sewer
Electricity
Maintenance
Chemicals
Interest
Depreciation
Sub total
General plant allocation:
Total
Total
cost
$ 14,500
5,800
9,914
163
829
15 , 004
65
24,480
34,815
$105,570
$105,570
Receiving
$ 7,250
2,900
45
828
687
1,255
$12,965
3,045
$16,010
Incineration
$ 5,800
2,320
9,914
163
235
3,498
2,918
5,300
$30,148
4,084
$34,232
Heat
recovery
$ 1,450
580
549
5,818
65
16,592
24,499
$49,553
5,775
$55,328
General
plant
$ 4,860
4,283
3,671
$12,90-',
*Based on 1978 dollars.
TABLE 21. MARYSVILLE NET OPERATING COST BY SYSTEM FUNCTION*
Net savings (cost)
of operation
Incineration
Incineration and
Heat recovery
($/yr) ($/Mg) ($/ton) ($/yr) ($/Mg) ($/tonj
Operating and
maintenance
Disposal savings
Energy savings
(34,232)
27,500
(28.53) (105,570)
22.95 27,500
23,557
(87.98)
22.95
19.63
( 6,732) (5.92) ( 5.61) ( 54,513) (47.93) (45.43)
* Based on 1978 dollars, 1200 tons annually.
Operating cost includes interest and depreciation.
In summary, the facility required an initial capital investment of
$509,949 in 1977. Of this amount, $77,302 was spent on the incineration
system to dispose of the solid waste and $432,647 was spent to recover and
utilize the energy. The anticipated net annual operational cost of the
facility in 1978 dollars would be $105,570 or $47.93 per Mg ($45.40 per ton).
The as-operated economics would produce an after tax positive cash flow of
$85,400 the first year and $7,600 for each year thereafter. The first year
value includes all of the 10 percent investment tax credit and the additional
10 percent energy credit effective in 1978.
59
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SECTION 4
OPERATING COST PROJECTIONS
EVALUATED FACILITIES
Since the two evaluated facilities at North Little Rock, Arkansas, and
Marysville, Ohio, were not operating at optimum conditions when they were
monitored, the cost and revenue for the as-operated conditions at each
facility were extrapolated to the optimum conditions. If the North Little
Rock facility had operated under optimum conditions, that is, with the feed
rate and steam production equal to the design capacities of 3.6 Mg (4 tons)
and 9090 kg (20,000 Ib) per hour, respectively, it would have had a total
revenue and a revenue per Mg (per ton) of refuse processed that would have
been $127,773 and $3.08 per Mg ($2.79 per ton), respectively, more than the
revenue for the as-operated conditions. The optimum operating costs are
given in Table 22, and the revenues are shown in Table 23. If the Marysville
facility had operated under optimum conditions, that is, with a daily feed
rate and energy recovery equal to the design capacities of 545 kg (1200 Ib)
and 6.17 GJ (5.85 MBtu), respectively, it would have yielded a savings of
$104,270 or $31.94 per Mg ($28.96 per ton) of refuse processed. The optimum
operating costs are shown in Table 24, and the revenues are shown in Table 25.
These revenues will give a payback within 5 years.
FACILITIES IN GENERAL
To estimate the operating costs at municipal and industrial facilities
in general, the 1978 economic data for the various operating parameters at
the two evaluated facilities were adapted in an empirical method to develop
equations expressing the relationship between the net loss or profit and
three independent parameters, namely refuse feed rate, shifts per week, and
operating percentage of rated capacity.
To determine the net operating costs of the municipal facilities, the
following assumptions were made: (1) the average employee salary is $20,800
per year including benefits, (2) the auxiliary fuel used is natural gas at
a unit cost of $0.088/k& ($2.50 MCF), (3) the electric power unit cost is
$0.035/kwh, (4) the unit cost of water is $0.24/k£ ($0.90/1000 gal), (5) the
ratio of the wet residue to the as-received refuse is 0.40, (6) the cost of
residue disposal is $4/Mg, (7) the interest rate is 7 percent, (8) the
estimated life of the facility is 15 years, (9) the heat content of the
refuse is 10.4 MJ/kg (4500 Btu/lb), and (10) the recovered energy value is
$0.00245/MJ ($2.60/MBtu).
60
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TABLE 22. NORTH LITTLE ROCK PROJECTED OPTIMUM OPERATING
AND MAINTENANCE COSTS*
Cost
Item
Salaries
Employee benefits
Fuel - no. 2 diesel
Natural gas
Gasoline
Electricity
Water and sewer
Maintenance
Replacement equipment
Residue removal
Chemicals
Interest
Depreciation
Other overhead
Total operating and
maintenance costs
($/yr)
$111
15
4
16
3
19
8
65
5
39
78
3
$370
,284
,750
,608
,704
,888
,237
,121
,656
—
t
,033
,179
,070
,209
,739
($/Mg)
$ 5
0
0
0
0
0
0
3
0
1
3
0
$17
.11
.72
.21
.77
.18
.88
.37
.02
—
t
.23
.80
.59
.15
.03
* Based on 1978 dollars.
(cist included in .salaries and employee benefit categories.
TABLE 23. NORTH LITTLE ROCK PROJECTED OPTIMUM
ANNUAL REVENUES*
Revenues Cost
Steam production $280,772
Tipping fees 24,336
Total $305,108
Per Mg of refuse processed (per ton) $14.02 (12.72)
* Based on 1978 dollars.
61
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TABLE 24. MARYSVILLE PROJECTED OPTIMUM OPERATING
AND MAINTENANCE COSTS*
Cost
Item
Salaries
Employee benefits
Fuel
Electricity
Water and sewer
Maintenance
Chemicalb
Interest
Depreciation
($/yr)
21,750
5,438
14,871
1,244
244
15,004
98
24,480
34,815
(S/Mg)
6.
1.
4.
0.
0.
4.
0.
7.
10.
66
66
55
38
07
59
03
49
66
Total 117,944 36.12
Based on 1978 dollars.
TABLE 25. MARYSVILLE PROJECTED OPTIMUM NET
OPERATION COSTS*
Cost
Item ($/yr) ($/Mg) ($/ton)
Operating and maintenance 117,944 36.12 32.76
Disposal savings 82,620 42.75 38.77
Energy savings 139,594 25.30 22.95
Net savings 104,270 31.94 28.96
* Based on 1978 dollars.
62
-------
To determine the net operating cost of the industrial facilities, the
following assumptions were made: (1) the average employee salary is $20,800
per year including benefits, (2) the auxiliary fuel used is natural gas at
a unit cost of $0.088/k£ ($2.50 kCF), (3) the electric power unit cost is
$0.035/kwh, (4) the unit cost of water is $0.24/k2, ($0.91/1000 gal), (5) the
ratio of the wet residue to the as-received refuse is 0.10, (6) the cost of
residue disposal is $4/Mg, (7) the interest rate is 12 percent, (8) the
depreciation period is 7 years, (9) the heat content of the refuse is
7.91 MJ/kg (7500 Btu/lb), and.(10) the recovered energy value is $0.00311/MJ
($3.28/MBtu). The higher energy value can be used because the industry is
the energy user and does not have to sell energy at a derated price.
The resultant data for the municipal and industrial facilities are
summarized in Figures 31 and 32, respectively, where the curves A through F
represent possible operational modes. In the development of these figures,
it was assumed that the refuse would be generated only 5 days per week.
The 7-day operational mode is burning a 5-day per week refuse generation
over a 7-day per week refuse processing. At 100 percent of rated capacity,
the net operating costs for 15 and 21 shifts per week in municipal systems
are nearly the same. As seen in Figure 31, the net operating cost per unit
of refuse feed rate is $10/Mg ($9/ton) or less for the capacity range
between 45 and 90 Mg/5 days (50 and 100 tons/5 days).
With refuse feed rates in the range of 27.5 Mg/5 days (25 tons/5 days)
and above, industrial facilities will yield a positive balance, or revenue,
in the net operating cost computation when they operate at 100 percent of
rated capacity but an actual cost in the net operating cost computation
when they operate at 50 percent of rated capacity. This cost must be
compared with the cost of alternative waste disposal methods and fuel
sources to determine the economic feasibility of a proposed system.
63
-------
30 (27.0)
A- OFF GRAPH
25 (22.-,)
20 (18.0)
(4.5)
REFUSE GENERATION RATE IN MgPD«, (TPD-,)
Figure 31. Estimated operating cost as a function of refuse feed rate,
shifts per week, and operating percentage of rated capacity
for municipal small modular incinerators.
64
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40 (36.0)
o
H
OS
fcj
P-.
20 (18.0)
10 (9.0)
JO (9.0)
20 (18.0)
_L
45
(50)
90
(100)
175
(150)
180
(200)
REFUSE GENERATION RATE IN MgPD., (TPD--,)
Figure 32. Estimated operating cost as a function of refuse feed
rate, shifts per week, and operating percentage of rated
capacity for industrial small modular incinerators.
-------
EPA REGIONS
U.S. EPA, Region 1
Solid Waste Program
John F. Kennedy Bldg.
Boston, MA 02203
617-223-5775
U.S. EPA, Region 2
Solid Waste Section
26 Federal Plaza
New York, NY 10007
212-264-0503
U.S. EPA, Region 3
Solid Waste Program
6th and Walnut Sts.
Philadelphia, PA 19106
215-597-9377
U.S. EPA, Region 4
Solid Waste Program
345 Courtland St., N.E.
Altanta, GA 30308
404-881-3016
U.S. EPA, Region 5
Solid Waste Program
230 South Dearborn St.
Chicago, IL 60604
312-353-2197
U.S. EPA, Region 6
Solid Waste Section
1201 Elm St.
Dallas, TX 75270
214-767-2734
U.S. EPA, Region 7
Solid Waste Section
1735 Baltimore Ave.
Kansas City, MO 64108
816-374-3307
U.S. EPA, Region 8
Solid Waste Section
1860 Lincoln St.
Denver, CO 80295
303-837-2221
U.S. EPA, Region 9
Solid Waste Program
215 Fremont St.
San Francisco, CA 94105
415-556-4606
U.S. EPA, Region 10
Solid Waste Program
1200 6th Ave.
Seattle, WA 98101
206-442-1260
pal 833
SW-797
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