Control of Air Pollution

                     From

            MUNICIPAL INCINERATORS
FOR TECHNICAL REVIEW ONLY NOT FOR PUBLICATION
        ENVIRONMENTAL PROTECTION AGENCY
            Office of Air Programs
 Bureau of Stationary Source Pollution Control
             Division of Compliance
             Durham, North Carolina
                August 1971

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TABLE OF CONTENTS
Page
LIST OF FIGURES iii
LIST OF TABLES v
INTRODUCTION vi
SUMMARY viii
1.0 PROCESS DESCRIPTION 1-1
1.1 Municipal Waste Composition 1-1
1.2 Process 1—4
1.3 Combustion and Gas Flow 1-6
1.4 Combustion Temperature and Cooling 1-8
1.5 Advanced Techniques 1-9
2.0 AIR POLLUTION EMISSIONS 2-1
2.1 Nonspecific Particulate Matter 2-4
2.1.1 Factors Affecting Particulate Emission 2-4
2.1.2 Measurements of Particulate Emissions 2-8
2.1.3 Characteristics of Particulates 2-8
2.1.4 Visible Emissions 2—13
2.2 Combustible Gas Emissions 2-14
2.2.1 Carbon Monoxide 2-15
2.2.2 Hydrocarbons and other Organics 2-15
2.3 Noncombustible Gas Emissions 2-19
2.3.1 Oxides of Nitrogen 2—19
2.3.2 Sulfur Oxides 2-19
2.3.3 Hydrogen Chloride 2-20
2.4 Metal Emissions 2-20

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TABLE OF CONTENTS
(continued)
Page
3.0 CONTROL TECHNOLOGY 3-1
3.1 Optimizing Combustion 3-1
3.1.1 Water-wall or Refractory Furnaces 3-3
3.2 Particulate Collection 3-5
3.2.1 High Voltage Electrostatic Precipitators 3-5
3.2.1.1 Design Parameters 3-7
3.2.2 Fabric Filters 3-11
3.2.3 Scrubbers 3-13
3.3 Performance Data 3-15
4.0 CONTROL COSTS 4-1
4.1 Capital Costs 4-3
4.1.1 Cooling Equipment 4-3
4.1.2 Gas Cleaning Equipment 4-6
4.2 Annual Operating Cost 4—6
4.3 Plant Cost 4-7
4.4 Use of the Cost Curves 4-18
4.5 Per Capita Cost of Air Pollution Control 4-21
5.0 RETROFITTING EXISTING MUNICIPAL INCINERATORS 5-1
6.0 REFERENCES 6-1
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LIST OF FIGURES
Figure Page
2-1 Effect of underfire air rate on furnace 2-6
emission
2-2 Histogram of particulate furnace emission 2-9
rates for municipal incinerators
2-3 Particle size distributions of furnace 2-12
effi uents
2-4 Histogram of calculated carbon monoxide 2-16
emission rates
3-1 Bulk electrical resistivity of entrained 3-9
particulates leaving three large, continuous
feed furnaces at six percent water vapor
3-2 Measured particulate loadings at four well- 3-17
controlled municipal incinerators
4-1 Flue gas conditioning systems total installed 4-4
equipment cost
4—2 Air pollution control systems--total installed 4-5
costs
4-3 Flue gas conditioning--annual operating cost, 4-8
including amortization and interest
4—4 Flue gas conditioning--annual operating cost, 4-9
including amortization and interest
4-5 Flue gas conditioning-—annual operating cost, 4-10
including amortization and interest
4-6 Air pollution control systems annual operating 4-11
costs, including amortization and interest
4-7 Air pollution control systems annual operating 4-12
costs, including amortization and interest
4-8 Air pollution control systems annual operating 4-13
costs, including amortization and interest
4-9 Average investment costs: continuous feed 4-14
systems rectangular construction
111

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LIST OF FIGURES
(continued)
Figure Page
4-10 Total operating cost versus plant capacity 4-15
for continuous feed, rectangular construction
units including amortization and interest
4-Il Estimated 1969 cost of incinerator plant with 4-16
boilers and precipitators
4-12 Total operating costs-—continuous feed water- 4-17
wall construction incinerator systems
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LIST OF TABLES
Table Page
0-1 Conversion factors ix
1-1 Estimated annual average refuse composition 1-2
as charged to municipal incinerators
1-2 Estimated national average refuse 1-3
1-3 Ultimate analysis of average national 1-3
refuse
2- 1 Air pollution emissions from uncontrolled 2-2
munici pal incinerators
2-2 Seasonal variations in refuse ash content 2-7
and particulate emissions
2-3 Composition of inorganic components of 2-10
fly ash
2-4 Properties of particulates leaving furnace 2-11
2-5 Emission rates of specific organic species 2-17
2-6 Furnace emission rates for polynuclear 2-18
hydrocarbons
2-7 Melting and boiling points of certain 2-22
metals and their oxides
2-8 Emission factors for selected metals 2-23
4-1 Effect of spray tower water evaporation 4-2
on flue gas properties
4-2 Installed costs 4-19
4-3 Total operating costs including amortization 4-20
and interest
4-4 Per capita cost of control 4-21
V

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INTRODUCTION
This document has been prepared to provide guidance to owners and
operators of municipal incinerators of greater than 4000 pounds per
hour refuse charging rate and to State and local control agencies
who will implement the standards of performance for new incinerators.
The standards were promulgated by the Administrator, Environmental
Protection Agency, on November 15, 1971,and published in the Federal
Register on the same date. The Administrator is authorized to develop
and promulgate standards of performance for new stationary sources
under Section 111 of the Clean Air Act (42 U.S.C. 1857 et seq) as amended
by the Clean Air Amendments of 1970 (Public Law 91-604).
In 1968, an estimated 27,100,000 tons of particulates were emitted
from stationary sources. These emissions are from combustion of fossil
fuels, industrial processes, and other miscellaneous sources. Municipal
incinerators emitted about 88,000 tons of particulates in 1968 or about
3.2 percent of the total particulates emitted from stationary sources.
There were approximately 250 municipal incinerators in the United States
in 1968 with a total capacity of 90,000 tons of refuse per 24-hour day. 2
Though emissions from municipal incinerators do not account for a large
fraction of particulates on a nationwide basis, individual plants can
be large point sources. Without control equipment, a modern plant
(300 tons per day capacity) will emit approximately 6000 pounds of
particulates per day. Municipal incinerators are usually located near
major metropolitan areas.
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The standard of performance applies only to municipal incinerators
with a capacity greater than 50 tons per day (24-hours), which burn
predominately municipal solid wastes. Municipal solid wastes include
household and convnercial paper, cardboard, garbage, yard wastes, etc.,
but does not include sewage sludge, pathological wastes, sawdust, or
other specialized trade wastes.
For municipal incinerators and for all other categories of stationary
sources for which performance standards are promulgated, either the
Administrator, Environmental Protection Agency, or the responsible
State will provide preconstruction review. Where the State has been
delegated authorization to implement and enforce the standards of
performance promulgated under Section 111 of the Act, the Administrator
will not provide preconstruction review for owners or operators. For
sources to be located in States which have not been so delegated this
authority, the Administrator will provide preconstruction review if
requested by the owner or operator.
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SUMMARY
Municipal incinerators discharge particulate matter and lesser amounts
of other contaminants. A performance standard is now being established
to limit the emission of non-specific particulate matter. Under Sections
ill and 112 of the Act, the standards may be revised and additional
standards may be adopted for other pollutants from incinerators. These
include sulfur oxides, nitrogen oxides, hydrocarbons, hydrogen chloride,
metals, and metal oxides. The present standard does not include “non-
criteria pollutants” as defined by Section 111(d) of the Act, and does
not therefore require the establishment of State standards for existing
incinerators.
The standard is:
0.1 grain of particulates per standard cubic foot (dry gas at
70 0 F and 1 atmosphere pressure) corrected to 12 percent CO 2
(by volume).
For the purpose of the standard, particulates must be measured by EPA
test methods.
The following table is provided for converting to other units. The
factors are fOr the typical municipal waste containing 26 percent
carbon.
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Table 0-1
Conversion Factors
1 Grain/SCF at 12% CO 2 (70°F, 1 atm.)
is equivalent to:
18.85 pounds/ton of refuse
1.71 pounds /1000 pounds flue gas at 50% excess air
1.92 pounds/l000 pounds flue gas at 12% CO 2
0.89 grains/SCF at 50% excess air
1.26 grams/Nm 3 at 7% CO 2 and NIP (0°c, 1 atm)
The performance standard applies to municipal incinerators being
charged with more than 50 tons per 24-hour day of solid waste, of
which more than 50 percent is municipal-type waste. Municipal
waste includes paper, wood, yard clippings, food waste, plastics,
leather, rubber, glass, rock, metals, and the like, which is
generally generated in homes, businesses, and small industries. The
standard does not apply to incinerators burning exclusively pathological
wastes or trade wastes such as sawdust, sewage sludge, or chemical
sludges.
The performance standard applies to any municipal incinerator whose
construction or modification begins after August 17, 1971. Since
construction requires 24 to 42 months, the first new incinerators to be
affected will not be operated until at least 1973.
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The performance standard is based on the best controlled plants in the
United States and Europe. Six incinerators in this country operate
particulate collectors designed for about 95 percent efficiency. Five
are electrostatic precipitators and one is a venturi scrubber. Many
plants in Europe have precipitators designed for 98 to 99 percent
efficiency.
Performance tests were made by EPA at two of the incinerators in this
country and two in Europe. The test data are presented in Section 3,
and show that average emissions at all four plants are less than the
standard allows. All four of the plants tested operate electrostatic
precipi tators.
One small Swiss plant (36 tons per day) with a fabric filter was tested
using European sampling procedures and reported emissions are well
below the standard. Still lower emissions are reported for a pilot plant
baghouse in Pasadena, California. The first large plants (‘ 5O tons per day)
equipped with baghouses will begin operations In late 1971 both here and
in Switzerland.
Test data for the venturi scrubber are not available. The designer has
however guaranteed an emission level consistent with the standard.
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Cost factors have been considered in setting the standard. Costs for
installing and operating control equipment are presented in Section 4.
For typical facilities, installation costs of control equipment are
less than about 15 percent of total plant cost and operating cost is
less than about 10 percent.
Per capita cost of particulate control is less than about one dollar
annually.
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1.0 PROCESS DESCIPTION
Conventional municipal incineration is a controlled combustion process
for burning municipal waste to gases and to a residue containing little
or no combustible material. When solid waste is exposed to a turbulent
atmosphere for a critical time period at an elevated temperature,
combustion occurs. During combustion, moisture is evaporated, and the
combustible portion of the solid waste is vaporized and then oxidized.
Concurrent reactions are the oxidation of metals and the oxidation of
such elements as sulfur and nitrogen. Carbon dioxide, water vapor,
ash, and non-combustibles are tne major end products of incineration
of municipal waste.
1.1 Municipal Waste Composition
Refuse burned at municipal incinerators contains a great variety of
material. The composition of municipal refuse, and its combustion
properties, have been the subject of a number of investigations. The
Arthur 0. Little study includes a survey of this wo,k and reports
findings from 23 separate data sets. Based on these data, the composition
of refuse, averaged throughout the year in the United States, was
computed. The results are shown in Table 1.1.
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Table 1.1
Estimated Annual Average National Refuse Composition
As Charged to Municipal Incinerators
Wt % Description
Glass 8.5 Bottles (primarily)
Metal 8.7 Cans, Wire, Foil
Paper 44.2 Various Types, Some
with Fillers
Plastics 1.2 Polyvinyl Chloride,
Polyethylene, Styrene,
etc., as found in
Packaging, Housewares,
Furniture, Toys, and
Nonwoven SynthetiCs.
Leather and Rubber 1.7 Shoes, Tires, Toys, etc.
Textiles 2.3 Cellulosic, Protein and
Woven Synthetics
Wood 2.5 Wooden Packaging, Furniture,
Logs, Twigs
Food Wastes 16.6 Garbage
Miscellaneous 1.7 Inorganic Ash, Stones,
Dust
Yard Wastes 12.6 Grass, Brush, Shrub
Trimmings
100.0
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The amount of yard waste in refuse was found to vary widely, depending
on local weather conditions and season. Miscellaneous material was
also found to vary widely depending on local situations and practices.
The amount of refuse in the remaining eight categories was found to
be fairly constant.
The average values of moisture, ash, heat content of refuse and u’timate
analysis were computed, as shown in Table 1.2 and Table 1.3.
Table 1.2
Estimated National Average Refuse
Moisture 28.16 wt. %
Ash 20.82 wt. %
Higher Heating Value 4450 Btu/lb (Water condensed)
Lower Heating Value 3900 Btu/lb (Water as vapor)
Table 1.3
Ultimate Analysis of Average National Refuse
Weight %
Moisture 28.16
Carbon (C) 25.62
Hydorgen (H 2 - bound) 2.65
Oxygen (0 - bound) 21.21
Hydrogen (H 2 ) 0.80
Sulfur (S) 0.10
Nitrogen (N 2 ) 0.64
Ash 20.82
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1:2 Process
The conbustion processes take place in the furnace of the incinerator,
which includes the grates and combustion chambers. There are numerous
designs or configurations of furnaces. No one design is considered the
optimum for all incinerator applications.
Furnaces commonly used for the incineration of municipal solid waste
are the vertical circular furnace, the multicell rectangular furnace,
the rectangular furnace, and the rotary kiln furnace. 3 Construction
can be either refractory or waterwall design.
The grate system must transport the solid waste and residue through
the furnace, and at the same time, promote combustion by agitation
and passage of underfire air. The degree and methods of agitation
are important. The abrupt tumbling encountered when burning solid
waste drops from one tier to another will promote combustion. Such
tumbling may contribute to entrainment of particulate matter in the
gas stream. Many designs incorporate continuous gentle agitation
which is purported to promote combustion and limit particulate
entrainment. Combustion is largely achieved by air passing through
the waste bed from under the grate, but particulate entrainment tends
to increase as a function of underfire air. 4 The entrainment of
particulate may be a minor consideration when high efficiency collectors
are employed.
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Grate systems may be classified by function, such as drying grate,
ignition grate, and combustion grate. Grates for solid waste
incineration may also be classified by mechanical type. They
include traveling, reciprocating, rocking, rotary kiln, circular,
vibrating oscillating, and reverse reciprocating grates, multiple
rotating drums; rotating cones with arms; and variations or combinations
of these types. In the United States, traveling, reciprocating,
rocking,rotary kiln, and circular grates are the most widely used.
Solid waste is charged to the furnace either continuously or in batches.
In the continuous process, solid waste is fed to the furnace directly
through a rectangular chute that is kept filled at all times to
maintain an air seal.
In the batch process, solid waste is fed to the furnace intermittently
through a charging gate or hatch, which is closed except when waste is
being charged. A ram can also be used to feed batches of material
directly to the grate through an opening in the furnace wall. Continuous
feed minimizes irregularities in the combustion system. Batch feeding
causes fluctuations in the thermal process because of the non-uniform
rate of feeding and intermittent introduction of large quantities of cool
air. Ram feeding does not introduce large quantities of cool air.
Siftings are fine materials that fall from the fuel bed through grate
openings during drying, ignition, and burning. Siftings consist of ash,
small fragments of metal, glass, ceramics, and unburned or partially
burned organic substances. Siftings are collected in troughs and conveyed
continuously to a residue collection area or returned continuously by a
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conveyor to the furnace. Siftings may also be removed batch wise.
Residue--all solid materials remaining after burning--includes ash,
clinkers, tin cans, glass, rock, and unburned organic substances.
Residue removal can either be continuous or intermittent. In a
continuous feed furnace, the greatest volume of residue is discharged
from the end of the burning grate; the remainder is siftings and
fly ash. Residue is normally quenched with water before removal from
the plant.
1.3 Combustion and Gas Flow
Time, temperature, and turbulence are commonly called the three l’s of
combustion. When solid waste is exposed for a sufficient time to a
turbulent, high temperature atmosphere, the waste can be satisfactorily
I nd nerated.
For a substance to burn, both surface and internal moisture must be
evaporated. During evaporation no burning takes place. Once moisture
is removed, the temperature can be raised to the ignition point,
although the outer surface of a solid may be ignited before the inner
material is completely dried. The drying process continues throughout
the furnace, but proceeds at the greatest rate immediately following
charging.
To facilitate drying, some furnace designs use preheated air or incor-
porate reflecting arches to radiate heat stored from the burning of
previously charged material. The first part of the grate system is
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frequently referred to as the drying grate. It is followed by a
section termed the ignition grate where burning is initiated.
Incineration is thought of as occurring in two overlapping stages,
primary combustion and secondary combustion. Primary combustion
generally refers to the physical-chemical changes occurring in
proximity to the fuel bed and consists of drying, volatilization,
and ignition of the solid waste. Secondary combustion refers to
the oxidation of gases and particulate matter released by primary
combustion. To promote secondary combustion, a sufficiently high
temperature must be maintained, sufficient air must be supplied,
and turbulence or mixing should be imparted to the gas stream.
Air that is supplied to the furnace from beneath the grates is termed
underfire air. Overfire air is introduced above the fuel bed; it
supplies oxygen to complete combustion, provides turbulence and any
needed cooling air. Infiltration air enters the gas passages through
cracks and openings and is frequently included in the figure for over-
fire air.
To supply adequate air for complete combustion and to promote turbulence,
a minimum of 50 percent excess air is normally provided. Too much excess
air, however, can be detrimental because it lowers furnace temperatures.
In general, refractory furnaces are operated with 150 to 200 percent excess
air, whereas waterwall furnaces require only 50 to 100 percent.
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1.4 Combustion Temperature and Cooling
Maximum furnace temperatures normally range from 2,100 to 2,500 9 F, but
may reach 2,800°F in localized areas. With refractory furnaces, the
gases leaving the combustion chamber are usually between 1,400 and
1,800°F. The gas temperature entering the stack can be expected to
be 1,000 0 F or less. Where induced draft fans, electrostatic precipitators,
and other mechanical devices are used, the gases have to be cooled
further.
Regulation of the combustion process and flue gas temperatures is achieved
through the introduction of excess air and water sprays and through
heat exchange. Of these, excess air is the most comon. In refractory
furnaces, it is often the only method of control.
Water injected into the hot gas stream cools the flue gas principally
through evaporation. Although water vapor adds to the gas volume as
does excess air, the total of water vapor and cooled gases Is smaller
than the original volume of gases. Water sprays are generally installed
downstream of the furnace.
Although heat exchange through the use of water tube walls and boilers
is not in widespread use in the United States, it is employed extensively
in Europe. A distinct advantage of heat exchangers is that no gases or
vapors are added such that significantly smaller gas volumes result.
Because gas volumes are greatly reduced, the size of collection devices,
fans, and gas passages also can be reduced. Heat recovery (usually
steam production) can bring further economies. Also, furnace temperatures
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can be more easily controlled in a waterwall furnace, and damage to the
furnace from overheating is not as great a hazard.
1.5 Advanced Techniques
Several advanced techniques for incineration of municipal waste are
being studied in the U. S. presently. These techniques fall into
three main categories: slagging incinerators, fluidized bed incinerators,
2
and pyrolysis.
Slagging incinerators involve either combustion at temperatures above
the ash slagging temperature or fusion of the ash as an additional
unit operation with more conventional incineration. The principal
advantages of this type incinerator are maximum refuse volume reduction,
destruction of all putrescible matter, low flue gas volume, and recovery
of a potentially useful product. Disadvantages are potentially higher
NO emissions, the need for auxiliary fuel, and greater operational
complexity and sensitivity.
Fluidized bed incinerators involve the application of fluidized bed
combustion technology for incineration of solid waste. Advantages
are simplicity of construction, complete combustion at low temepratures,
low flue gas volume, and ease and efficiency of intermittent operation.
disadvantages are 4 e necessity of feed preparation, high flue gas particulate
loading, operational complexity and sensitivity, small unit capacity, and
higher power consumption and cost.
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Pyrolysis involves the autogenous thermal decomposition of refuse to
produce combustible organic gases, liquids, and char. The process
should facilitate the control of air pollution since it is completely
contained. In addition useful products might be produced, and the
process is self—sustaining with respect to energy. Potential disadvantages
are difficult to assess due to the lack of experimental data.
None of these techniques have been applied to full-scale units. Stages
of development vary from conceptual design to pilot plant studies.
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2.0 Air Pollution Emissions
There is a greater variety of air pollutants discharged from municipal
incinerators than from nearly any other source category. In addition,
the emission rate for each pollutant varies considerably from day to day
and week to week as a function of refuse composition.
For the most part, emissions are the products of wastes burned In the
incinerator. Inorganic ash, carbonaceous solids, combustible and non-
combustible gases, metal fumes, and mercury vapor are all evolved from solid
wastes under the turbulent high temperature oxidizing atmosphere created
in the furnace.
Only one pollutant - nitrogen oxides - appears to be Independent of the
refuse makeup, and NO formation may be partially Influenced by the
nitrogen content of the solid waste.
In this section air pollution emissions are considered in the forms and
concentrations that they are released from conventional incinerator
furnaces. The reduction and changes which may t effected in control
devices are treated in Section 3,0,
Emission factors from two different reference sources are presented In
Table 2-1 for seven of the more prevalent air pollutants released from
municipal incinerators. Both represent extensive literature surveys of
measured data for existing incinerators of varying design. They do not
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Table 2-1
AIR POLLUTION EMISSIONS FROM UNCONTROLLED
MUNICIPAL INCINERATORS
Pollutant
Emissions
Littlea
Range, lb/ton
McGraw & DuDrevb
Emissions Average lb/ton
Li ttI ea M r , _ & pu e.yb
c. Test methods include measurements
Test Code and other non-specified
with both EPA method, ASME Power
tehcniques.
d. Includes data for both controlled and uncontrolled incinerators.
e. Uncontrolled particulates from furnace.
f. Particulates from units equipped with low efficiency collection system
(settling chamber plus water sprays).
Particulates , Uncontrolled
Particulates , Controlled
1 • 6197 d
d
8-7O
3—35
197 d
d
30;
14
Carbon Monoxide
0.0-233
0.3-4.0
34.8
1.0
Hydrocarbons (as CH 4 )
Oxides of Nitrogen (as NO 2 )
Sulfur Oxides (as SO 2 )
Hydrogen Chloride
Polynuclear Hydrocarbons
0.09-6.3
1.4-5.4
-5
3xl0_. —
4x10
2.7
3.0
3.9
1.0
0.005
1.5
2.0
1.5
a. Little (Reference 2).
b. McGraw and Duprey (Reference 18).
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reflect emissions from furnaces of the most modern design. The widest
difference in reported values concerns carbon monoxide. Little reports a
considerably greater emission factor (34.8 lb/ton) than McGraw and DuDrey
(1.0 lb/ton) for this pollutant.
Differences in hydrocarbon, nitrogen oxides and sulfur oxides figures are
not significant in view of the limited testing for these pollutants and the
questionable test procedures which probably were employed In many cases.
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2.1 Non-specific Particulate Matter
Furnace exhaust gases normally carry a variety of particulates Including
inorganic ash, organic liquids and solids, and fumes from low boiling metals.
The performance standard includes a limit only for non-specific particulates
covering all of these forms.
The mechanisms by which the various particulates are formed and entrained
in exhaust gases have been considered in various publications. Many
approaches to particulate control have in fact been aimed at minimizing such
releases from the furnace. While extensive studies have been undertaken,
none have been successful as yet In reducing particulate emission from
conventional incinerators to the limit of this performance standard. The
most promising mechanisms involve pyrolysis (Section 1) and incorporate
considerably different furnace design and operation,
Particulates can be divided into two general categories i.e. entrained fly
ash and pyrolysis products. Fly ash composition normally resembles the
furnace ash closely, with inorganics predominating. Pyrolysis products
are principally organic but include inorganics such as metal fume and
hydrogen chloride. Under optimum combustion conditions the organics can be
oxidized to carbon dioxide and water. Specific metal fumes and vapors
are discussed in Section 2.4.
2.1.1 Factors Affecting Particulate Emission
At existing incinerators fly ash entrainment is the result of refuse
agitation and mixing of air and refuse. Historically, under fire air has
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been a principal factor. Particulate emissions from furnaces generally
increase with air velocity through the bed of burning refuse.
Test data of Little showing the effect of underfire air velocity on furnace
emissions, is reproduced in Figure 2-1. These data were obtained from a
small test unit (solid line in the figure) and from municipal incinerators
(broken lines). The municipal incinerators ranged in size from 50 to 250
TPD and included traveling, rocking, and reciprocating grates. Except for
the traveling grate data (circles in the figure), a strong dependence of
furnace emissions on underfire air velocity Is evident.
Underf ire air rates may vary between 10 and 100 SCFM per square foot of
grate. At a bed temperature of 2000°F, the resulting linear air velocity
is 0.8 to 8 feet per second. Based on these velocities, and settling
velocities of ash particles, it appears that underfire air will entrain
particles up to about 400 microns in diameter. The larger particles
would be expected to settle In downstream passages of low velocity.
The combustible portion of particulates depends in large measure on the
efficiency of burning pyrolysis products. A relatiqnship is suspected
between combustible particulates and combustible gases although there are
no data on the subject. Particulate catches in incinerator control devices
have been found to contain 5 to 40 percent combustibles by weight with an
average of 15 percent. No correlation has been developed between combustible
particulates and furnace parameters.
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PHS Field Test (20) \
40.0 (250 Tnn 2 Sect Tray. Grate)
20.0 -
. Walker and Schrnitz D.t (2 $
10.0 — - - .- _________- - 1) 250 -TPD Reciprocating Grate
o ?bO TPD 2 Sect. Tray. Grate
8.0 * 12O TPD Rocking Grate
HSF,e (dTest (2O
6.0
(50 tpd Unit)
4.0
.
2.0 IncInerator (1 q)
and 50% Mo
10 — ______________
0.8 :
1 \ (25% O.M8 i tureFueU
0.6
W 0.48V
0.4 -
0.2
1 1111 i1 1 1 1 IHIII I .1 1 11111
0.1
1 4 6 8 10 20 40 6080100 200 400
c : M Undert ire Air Per Sc . Ft. Grate Area (V
FIGURE -.j. EFFECT OF UNc E FRE AIR RATE ON FURNACE EMISSION
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The ash content of refuse also has a strong influence on furnace emissions,
as shown by data in Table 2-2. These data were obtained from municipal
incinerators operating in Germany, where the ash content of refuse varies
greatly with the seasons. Particulate emissions were found to vary nearly
tenfold during the year. The greatest refuse ash content and furnace emissions
occur in January when there are large fractions of coal ash and wood ash
in the feedstocks. Conversely, the lowest ash and particulate emissions
occur in August when there Is a far less ash from home burners.
TABLE 2-2
SEASONAL VARIATION IN REFUSE ASH CONTENT
AND PARTICULATE EMISSIONS
Refuse Ash Particulate Emissions
Month Content, Percent ( grams/Nm 3 ) (lb/ton refu! j
January 44.5 15 225
February 38 12.8 192
March 30.5 9.3 139.5
April 27 7 105
May 22 5.3 79.5
June 18 4 60
July 12.5 2.3 34.5
August 10.5 1.9 28.5
September 14.5 2.7 40.5
October 26 5.7 85.5
November 35.5 10 150
Decembey 43 13.7 205.5
Source: Data for incinerators in Germany from Arthur D. Little Report,
Table V-3.
2-7

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2.1.2 Measurements of Particulate Emissions
Little has collected the known published ‘rate data for furnace emissions.
These are shown in Figure 2-2 for furnaces larger than 50 TPD. Incinerators
in both Europe and the United States are included.
The median value for all reported cases is 24 lb/ton of refuse. This
number is probably biased by the large numbers of reported cases for a
few plants.
To obtain an average value for United States plants, Incinerators were
classified according to grate type. Median emission rates for each type
were-determined. These values were then weighted according to the number
of U. S. Incinerators of each type. The average particulate emission
rate, so determined, was found to be 19.7 lb/ton of refuse. The value Is
in approximate agreement with the range cited by McGraw and Duprey for controlled
and uncontrolled existing incinerators.
2.1.3 Characteristics of Particulates
The chemical makeup and particle size distribution of particulates varies
with refuse composition and with the design and operating conditions of both
the furnace and control device.
About 15 percent of the fly ash is combustible, including carbon and complex
hydrocarbons. The remaining 85 percent is noncombustible, mineral matter.
Kaiser 6 determined compositions for the mineral portion of fly ash, from
2-8

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-------
two incinerators in New York City. His findings are shown in Table 2-3.
About half the mineral fly ash is silicon dioxide and about one-quarter
aluminum oxide. Various metallic oxides and sulfates make up the remainder.
Sulfate concentration is higher than would be expected from refuse sulfates.
The sulfate particles are perhaps formed by the reaction of metal oxide
particles with sulfur dioxide
The variability of fly ash from plant to plant 1 or In a given niant, is
not known. Many more data are needed to determine composition ranges.
Table 2-3
Composition of Inorganic Comronents of Fly Ash
Component New York City Incinerator
73rd St. So. Shore
Si0 2 46,4 55.1
AL 2 0 3 28.2 20.5
Fe 2 0 3 7.1 6.0
CaO 10.6 7.8
MgO 2.9 1.9
Na20 3.0 7.0
K 2 0 2.3
Ti0 2 3.1
SO 3 2.7 2.3
Particles si ze distributions of furnace emissions at three U.S. Incinerators,
have been measured by Walker & Schmitz 5 these data are shown in Table 2-4,
and Figure 2 3. It Is seen that fly ash contains many fine particles with
about 20 percent being 5 microns or smaller. Most of the fine particles
and essentially all of the large particles would have to be collected to
2-10

-------
meet the performance standard, which requires an overall collection
efficiency around 90 percent.
Data from a single European incinerator, as measured by Andritzky 16 , is
included in Figure 2-3 for comparison. It is seen that the three United
States plants have higher fractions of fine particles,
Table 2-4
PROPERTIES OF PARTICULATES LEAVING FURNACE
Physical Analysis Installation
1 2 3
____ (‘26O r PO) (250 TPD) (250 TPD)
Specific gravity
(gm/cc) 2,65 2.70 3.77
Bulk Density (lb/cf) 30.87 9.4
Loss of ignition at
750 C (%) 18,5 8.15 30.4
Size distribution
(%) by Weight)
< 2 13.5 14.6 23.5
16.0 19.2 30,0
< 6 u 19.0 22.3 33.7
< 8 21.0 24.8 36.3
-------
95
0.1 1.0 10.0
Particle Diameter. Microns
Sources: European: Anóitzky. M., Brennstotf-WármeKraft 19(9). 436(1967)
U.S.A.: Walker 1 A B and Schmitz 1 FW. Proc. 1966 ASME Nat 1. lncin. Conf.. pp 64-73
N)
-a
100.0
FIGURE -j PARTICLE SIZE DISTRIBUTIONS OF FURNACE EFFLUENTS
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2.1.4 Visible Emissions
Visible smoke emissions are a function of particulate concentration and
particle size. It has not l:een possible to obtain an absolute correlation
between visible emissions and particulate concentrations for municipal
incinerators or other sources of particulates. Neverthe1ess for any
given source low particulate concentrations are associated with lesser
opacities.
With smaller incinerators used to burn standard comercial and apartment
house wastes, it has been possible to eliminate visible emissions when
particulate loadings are 4 to 6 pounds per ton (0.2 to 0.3 grains per SCF
corrected to 12 percent C0 2 ). Typical retort multiple chamber incinerators
of 100 to 1000 pound per hour capacity can be!operated consistently with
no visible emissions if recomended operating practices are followed.
With municipal incinerators visible particulates tend to be more prevalent.
The better controlled U.S. incinerators operating at 4 to 6 pounds of
particulate per ton exhibit visible emissions of up to 40 percent opacity.
Opacities are frequently less than 40 percent but seldom less than 10
percent. None of the controlled U.S. incinerators operate with a clear
stack although several European units have been observed to do so during
limited periods when recordings have been made.
Uncontrolled or partially controlled municipal incinerators (settling
chambers, coarse water sprays, mechanical collectors, etc) are characterized
by dense white to brown smoke or 60 to 100 percent almost continuously.
2-13
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Many of these units are capable of meeting a black smoke limit of No. 4
Ringelmann indicating that most of the carbonaceous matter has been
burned from the fly ash. This observation is consistent with the
average fly ash combustible content of 15 percent cited by Little.
Smoke observations and stack tests have led to the hypothesis that fly
ash from municipal Incinerator furnaces contains greater concentrations
of fine particles (<10 microns) than fly ash from apartment house and
comercial Incinerators. If the hypothesis is correct, the fine particles
probably are metal fume and liquid droplets resulting from the condensation
of high boiling organics. There is generally less segregation of wastes
at municipal incinerators than at smaller incinerators such that refuse
usually contains significant quantities of metal and heavy plastics. Low
boiling metals such as lead, tin, zinc and cadmium tend to vaporize in the
furnace and condense as a very fine fume The relative concentrations
of fine particles may be of less impact if high efficiency particulate
collectors are employed with new incinerators.
2.2 Combustible Gas Emissions
Combustible gases discharged from municipal incinerators include carbon
monoxide, hydrocarbons, aldehydes, organic acids and other organics.
All combustibles--gases, liquids, and solids—-result from the incomplete
combustion of carbon compounds. Gases and liquids are pyrolyzed from the
refuse. Incomplete gas combustion is attributed to inadequate mixing of
air with pyrolysis gas and to flame quenching at the furnace walls, rather
than inadequate furnace residence times. This conclusion is based on a
2-14
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comparison of reaction rates and actual furnace residence times.
2,2.1 Carbon Monoxide
Published carbon monoxide emissions 2 are shown in Figure 2.4. These mass
emission values were calculated from measured concentrations of carbon
monoxide and carbon dioxide. In most cases, stack gas flow rates were
not measured. Emission values were calculated from a mass balance based
on an assumed carbon content of 25.6 percent, the national average for
wastes burned in municipal incinerators,
The data in Figure 2-4 were averaged for each plant type and weighed by the
frequency of individual furnace types of the United States. The national
average emission factor so obtained, is 34.8 pounds of carbon monoxide per
ton of refuse burned. This value is considerably higher than the figures
reported by McGraw and Duprey (range 0.3 to 4.0, average 1.0 pounds per ton).
The variations are attributed to the limited test data available and to
the possibility of inaccurate testing procedures. Recent EPA tests of a
modern incinerator in Dade County, Florida, showed 108 ppm at 287 percent
excess air or 42 pounds of carbon monoxide per ton of waste burned.
There are no reliable data showing the instantaneous fluctuations of carbon
monoxide over normal operating periods.
2.2.2 Hydrocarbons and other Organics
Several combustible organic compounds have been identified in stack emissions
2-15
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—
76
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A 1,tso.uI Eoi Nu R Ossi
No. Cous -0 PNot No. Emiulon R.N
9 1 2 l lIWton
8 6 241
6 35 211
9 52 185
10 54 217
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Cgbon Monoiide Emiuion Pounds psi Ton of 1 efusi
FIGURE HISTOGRAM OF CALCULATED CARBON MONOXIDE EMISS1ON
RATES (Pounds per Ton of Refuse)
2-16
To 103
t
26
20
15
10
5
99
15
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—
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20 30 40 50 60 70 80 90 100 ItO 120 130 140
-------
from municipal incinerators. Presumably, these compounds result from incom-
plete combustion of pyrolysis gas, generated from burning refuse.
Principal components are hydrocarbons and partially oxidized hydrocarbons.
The limited data are summarized in Tables 2.5 and 2-6.
greatest for hydrocarbons, and least for organic acids.
Variations are
TABLE 2—5
EMISSION RATES OF SPECIFIC ORGANIC SPECIES
Hydrocarbons Organ9c Acids Aldehydes as
Plant No.* as CH 4 as Acetic Acid Formaldehyde
0.27
0.46
2.41
0.09
0.2
6.3
3.94
2.6
0.32
0.16
0.11
<0.14
<0 08
<0.08
0.1
0.1
0.06
0.06
0,099
0.033
0.02
0.30
0.16
0.024
O .09
O .03
0.001
0.28
O .24
0.075
0.058
0.263
0.188
0.397
O .015
0 • 041
0.840
0.612
0.190
0.231
Burning Garbage
Start—up
Notes
57
14
70
103
5
Start-up
Average 1 .84
Standard 2.16
Deviation
*Table J 1, Appendix J, Reference 2
Burninci Garbacie
2—17
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TABLE 2-6
FURNACE EMISSION RATES FOR POLYNUCLEAR HYDROCARBONS
Polynuclear
Hydroca rbons
(grams per ton
No. Type of Unit refuse)
1 250-ton/day Municipal (before 0.035
settling chamber)
2 50-ton/day Municipal (before 0.284
scrubber)
3 50-ton/day Municipal (after 0.015
scrubber)
4 5.3-ton/day Commercial Single 1.92
Chamber
5 3-ton/day Commercial MultIple 1.94
Chamber
-Average PNH emission factor: 4.2 x lb/ton of refuse
Polynuclear hydrocarbons listed in Table 2-6 include pyrene, fluoranthene,
and lesser amounts of other polycyclic organic matter, These compounds
constitute a very small percentage of total emissions, but are of interest
L cause of their possible influence on human health.
Certain organic compounds known collectively as polychiorinated biphenyls
(PCB), have been found to accumulate In the fatty tissue of birds and
fish. Possibly the PCB’s interfere with biological functions. Certain
plastics in municipal refuse contain PCB’s and may produce emissions during
incineration. Testing is now being done to detect and measure PCB’s in
stack gases.
2-18
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2.3 Noncombustible Gas Emissions
The principal noncombustible gases reledsed from municipal Incinerators
are nitrogen oxides, sulfur oxides, and hydrogen chloride.
2.3.1 Oxides of Nitrogen
The major components of air-nitrogen and oxygen-react at elevated
temperatures to form nitric oxide (NO). Further oxidation partially
converts NO to nitrogen dioxide (NO 2 ). Total oxides of nitroqen (Nfl )
are measured collectively and reported as NO 2 .
Little cites emission data for NOR’ obtained from 21 tests at municipal
incinerators and 78 tests at small pilot plants. Based on these data,
any average emission factor of 3 pounds NO 2 per ton of refuse, was determined
for municipal Incinerators tn the United States. On a dry volumetric
basis, the corresponding stack gas concentration of NO 2 is about 200 ppm
at 50 percent excess air.
2.3.2 Sulfur Oxides
Sulfur compounds (usually sulfates and sulfides) are present in municipal
wastes, especially In paper, food waste, garden waste, and rubber. On
the average, refuse contains about 0.1 percent sulfur, a low figure
compared to most coal and fuel oil.
2-19
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During incineration, some of the sulfur compounds are converted to sulfur
dioxide (SO 2 ) and possibly sulfur trioxide (SO 3 ) as well, Very little
data are available to determine representative SO 2 emissions. Based on
a critical analysis of available data from 13 plants, Little estimated
that on the average, about 3.94 pounds of SO 2 are emitted per ton of municipal
refuse burned. This is equivalent to a stack gas concentration of about
185 ppm volume, dry basis, when operating at 50 percent excess air.
2.3.3 Hydrogen Chloride
Polyvinyichioride is commonly used for packaging and for many the consumer
products In the United States. It is found increasingly in municipal
refuse, along with other chlorinated plastics. During incineration, hydrogen
chloride is formed and discharged with the furnace gases. Other chlorine
compounds such as phosgene are also suspected to be present in minor
concentrations.
Data on emission rates of hydrogen chloride are not presently available.
Based on average refuse composition, Little estimates that about 0.99
pounds of hydrogen chloride is emitted per ton of refuse burned. For
furnace operation at 50 percent excess air, dry stack gases would contain
about 85 ppm by volume.
2.4 Metal Emissions
In addition to the pollutants mentioned above, five metallic elements and
2-20
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their compounds deserve attention, because of their possible impact on
human health. They are mercury, beryllium, cadmium, zinc, and lead.
Very little Is known about emission rates for these metals from municipal
incinerators, but testing Is underway to detect and measure them.
The metals are known to be In various items making up municipal refuse.
All five metals are used as alloys in the production of certain steels
and other metals. Beryllium acts as a hardening agent in copper alloys.
Cadmium serves in bearings, and the electroplating of irorr, Lead is used
for the manufacture of pipes, acid resistant linings, paint plgments,brass,
bronze, and as solder for tin plate cans, Zinc is frequently plated on
steel to resist corrosion:. All these items are found in municipal refuse.
Mercury is used as a catalyst In the manufacture of certain plastics, and
residual amounts may be contained in the products. The content of plastics
in municipal refuse is now about 1 percent, and growing steadily, Mercury
is also used In manometers, electrical switches, and amalgams.
Melting and boiling points of the five metals and their stable oxides,
are given in Table 2—7. At furnace temperatures all five metals and lead
oxide melt, and liquid droplets are possibly entrained by underfire air.
2-21
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Table 2 7
MELTING AND BOILING POINTS OF CERTAIN METALS
AND THEIR OXIDES
“ ta1 Melting Point Boiling Point Metal Oxide Melting Point Boiling Point
°F
Ig -38 671 HgO d. 931 -
3e 2335 5385 BeO 4590 7050
610 1411 CdO >3130 d.
Pb 620 2950 PbO 1630 ?
787 1661 ZnO >3270 3270
= decomposes
Furnace temperatures are sufficiently high to boil mercury, cadmium, and zinc.
Lead and beryllium are partially vaporized. Upon cooling, the fumes condense
to form solid particles that are generally very small and remain entrained
with the flue gases.
Metal oxides are produced by combustion of the metals In the furnace. Fine
ash parttcles that form can Lecome entrained by underfire air. Fumes can
also form by partial vaporization of the oxides of zinc, beryllium, and lead.
During a recent test for particulates at a U.S. incinerator equipped with
a modern electrostatic precipitator, 350 millograms were collected in an
EPA sampling train. This sample was analyzed for metals by atomic adsorption.
From the results, emission factors in Table 2-8 were calculated.
2-22
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Table 2-8
EMISSION FACTORS FOR SELECTED METALS
Metal Emission Factor
(lbs/ton of refuse charged)
Sodium 0.18
Potassium 0.25
Magnesium 0.007
Calcium 0.052
Iron 0.0023
Aluminum 0.02
Nickel 0.0078
Cobalt 0.0
Manganese 0.0005
Copper 0.002
These emission rates are not representative of incinerators at large. They
result from a single source test at a well controlled incinerator, and are
given to illustrate the variety of metals in stack gas emissions. Additional
testing is being done to provide more extensive data.
2-23
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3.0 Control Technology
In order to meet the standard of performance, owners and operators of
municipal incinerators will find it necessary to: (1) optimize com-
bustion of carbonaceous materials and (2) install and operate high
efficiency particulate collectors. If standards are established for
additional pollutants in the future, further remedial action may be re-
quired to prevent release of gaseous emissions including both combustibles
arid non-combustibles.
3.1 Optimizing Combustion
Nearly complete combustion will minimixe emissions of unburned solids as
well as hydrocarbons, carbon monoxide, and partially oxidized organics.
Optimum combustion conditions include reasonable turbulence, an excess of
oxygen, adequate time, and sufficient temperature to drive the oxidation
reactions to completion. Combustion has to take place in the incinerator.
It is not likely that any control devices will be utilized to complete
combustion downstream of the incinerator or to remove any substantial
quantity of combustible gases or vapors.
From the standpoint of air pollution control and solid. waste management,
municipal incinerators should be designed and operated to provide maximum
burnout of all combustibles in the ash residue and in the exhaust gases.
Incinerator design necessarily concerns many aspects of solid wastes
3-1
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handling which are not within the scope of this document. For such
guidance, the Office of Solid Waste Management Program has published
pertinent information in its t ’Incinerator Guldelines--1969 ,” available
from the U.S. Government Printing Office, Washington, D.C. 20402.
It is not the intent of this document to consider all aspects of incin-
erator design. Nonetheless, certain factors that strongly affect the
release of air pollutants and the costs of controlling them are cited.
Designers of incinerators covered by the perfonnance standards should
give careful consideration to the following points:
(1) sufficient turbulence should be provided in the system to
allow nearly complete burnout of both solid wastes and airborne
combustibles. Poor mixing conditions and incomplete combustion
should not be allowed as a tradeoff for low particulate entrain-
ment to the collectors.
(2) excess air should be held to a reasonable minimum such that
furnace temperatures will be sufficient for good combustion and
the volume of resultant stack gases will not be excessive. Air
pollution control costs are in direct proportion to gas volume.
(3) the incinerator should be constructed of materials that with-
stand temperatures necessary for essentially complete combustion.
3-2
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(4) incineration temperatures greatly in excess of present practice
may generate significantly larger quantities of nitrogen oxides,
metal fume, and hazardous materials in the exhaust gases.
(5) visible emissions increase during periods when soot is blown
from boiler tubes, and when precipitator electrodes are rapped. To
insure minimum visible emissions, those operations should be performed
at frequent intervals. Excessive particulate build ups will thereby
be avoided.
(6) steady state operation is important for optimum performance
of the incinerator and pollution control equipment. The refuse
charging rate, furnace temperature and gas flow rate should be
maintained as constant as possible. Continuous feed systems, induced
draft fans and automatic controls tend to promote steady state con-
ditions.
3.1.1 Water-Wall or Refractory Furnaces - Both types of furnaces can be
designed and operated to provide optimum combustion conditions. To date,
most of the United States installations have been of full refractory
construction. Nonetheless, steam producing water-wall units present
advantages from the air pollution control standpoint. These include: (1)
lower excess air and higher resultant furnace temperatures; (2) lesser
volumes of exhaust gases to be handled by particulate control equipment;
(3) cooler exit gas temperatures such that there is less need for auxiliary
cooling with water sprays or dilution air.
3-3
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Most of the modern, well controlled European municipal incinerators are
of water-wall construction. At these installations, particulate emissions
are held to low levels through the use of high efficiency electrostatic
precipitators. Revenues are derived from the sale of steam to power
plants and industries.
Water-wall furnaces have their d4sadvantages. They add to the capital
costs of the incinerator and to the complexity of operation. Obviously,
they must be operated nearby a steam consumer, such as an electric power
station or central heating plant. Maintenance problems are greater and
tube corrosion can be appreciable where there are significant concen-
trations of acid gases. Soot blowing of tubes is required periodically
and resultant emissions may exceed the capability of the particulate
collector.
The principal disadvantage of refractory furnaces are their inherent
temperature limitations and relatively large heat soak characteristics.
At many existing incinerators, large quantities of excess air are added
to the furnace solely to prevent overheat damage to the refractory.
The results are low furnace temperature and large exhaust volumes to be
handled by particulate collectors. Heat soak can be a disadvantage
where refractory furnaces are operated for only one shift per day. The
furnacescome up to temperature slower than water wall units.
3-4
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3.2 Particulate Collection
High efficiency electrostatic precipitators, venturi scurbbers, and
fabric filters are the only devices which have shown the capability
of meeting the standard of performance for particulate emissions.
There has been considerably more experience with precipitators than
with the other two systems. The most efficient particulate removal
systems for municipal incinerators are located in Europe.
In terms of normal operating conditions (six percent CO 2 and 400°F),
the particulate standard of 0.1 gr/scf dry at 12% Co 2 means that particulate
loadings cannot 1 exceed 0.028 grains per acf. Where excessive dilution
air is introduced into the system, particulate loadings will have to
be significantly less than 0.028 grains per acf.
In light of available control devices, the performance standard appears
readily attainable. In fact, it is anticipated that considerably better
performance will be realized when operators install and operate high
efficiency collectors.
3.2.1 High Voltage Electrostatic Precipitators - Single stage or high
voltage electrostatic precipitators have been employed more widely with
municipal incinerators than any other high efficiency collector. Several
units of 99 percent rating have been installed in Europe, Australia, and
Japan. Their use with United States and Canadian incinerators has been
a more recent development. The first U.S. incineratorsso-equipped are
3-5
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the Dade County (Florida) unit (96 percent efficiency) which went into
operation in August 1970, and two New York City units that were installed
in 1969. A few others are being put into service in 1971. The highest
rated efficiency (97 percent) is reported for the Northwest Incinerator
installed for the City of Chicago in 1971.
To date all precipitators used with municipal incinerators have been of
plate and wire design operated at 30 to 100 kilovolts. Collector solids
are removed from the plates by mechanical rapping. Hoppers may be operated
dry or sluicing with water may be employed. Irrigated pipe and wire
precipitators have not been used with municipal incinerators but probably
could be adapted.
Electrostatic precipitators are more sensitive to changes in gas flow
conditions, than scrubbers or baghouses. They do not remove gaseous con-
taminants. Steam plumes occur only when large amounts of cooling water
are used. Unless water sluicing of collection hoppers is employed, the
particulates can be removed in the dry state.
Temperature and humidity strongly affect the operation of an ESP. Tem-
perature affects both the electrical resistivity of the particulates (there-
fore their collection response) and the operating potential of the ESP.
Humidity also affects resistivity. It is sometimes important to pretreat
incinerator gases with spray water and/or cooling air to provide desirable
levels of humidity and temperature.
3-6
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Rated Efficiencies — Vendorsnormally guarantee an efficiency based on
specific operating conditions, inlet loading and sometimes on the size
of particulates. In the past most guarantees have been based on the ASME
Power Test Code. Compared to EPA methods, the ASME test procedure normally
shows lower grain loadings and correspondingly higher efficiencies.
3.2.1.1 Design Parameters - Electrostatic precipitator design is highly
specialized to the point that much of the detailed empirical inforniation
is known only by the few firms that design the equipment ‘comercially.
It is usually not possible for a reviewing engineer in a State or local
agency to obtain as much background information as he desires on proposed
precipitators. He must rely on the designer to a greater degree than is
the case with other comon control equipment.
The wide variation in solid wastes burned in municipal incinerators presents
a design problem which is unlike many industrial process applications where
the characteristics of particulates are much more consistent. To assure’
day-to-day compliance with the performance standard, a precipitator must
be designed and sized to accomodate the most adverse conditions of tem-
perature, humidity, and resistivity that are likely to occur.
Principal design factors include operating voltage, gas temperature and
velocity, flow distribution, residence time, surface area of collecting
electrodes, number and geometry of discharge electrodes, electrode spacing,
rapping system, and structural materials. 10, 11 , 12, 13 Ramsdell 12 has
3-7
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presented one of the few empirical approaches to precipitator design.
He relates performance to collection surface, velocity, electric current
capacity, and the number of individual buss sections. The relationships
were developed for coal-fired boilers and may not apply directly to
municipal Incinerators.
Resistivity - Electrical resistivity of the fly ash is a property of prime
interest when utilizing electrostatic precipitators. Particles with
excessively high or low resistivity cause disturbances in electrical
operation that complicate design and increase capital costs. In general,
collection of particulates with higher resistivities requires larger and
more expensive preclpltators. Very low resistivities are also troublesome,
but reportedly can be handled In properly designed precipitators. When
the resistivity is low, the dust readily loses its charge to the collecting
electrode allowing reentrainment of the particle.
The optimum range for efficient operation of an electrostatic precipitator
is reported by White 11 to be between 1O 4 to 1010 ohm-cm. Typical resistivity-
temperature curves of entrained particulates leaving large continuous feed
refractory furnace incinerators were charted by Walker (Figure 3-l).
Temperature - The selection of an operating temperature should involve
careful consideration of the resistivity of the particulate. As indicated
by Figure 3-l,the high resistivity zone ranges from about 2000 to 500 0 F for
typical particulates. This temperature zone should be avoided if possible.
Operation below 200 0 Fcan be accomplished by cooling with heat exchangers
and/or water sprays. In such cases reheating is desirable for close control
of temperature and humidity. Precipitators have been operated at 750 0 F and
temperatures up to 1000°F probably are feasible. At temperatures above 500°F
3-8
-------
‘1
.1
. /
Faiurc é. Bulk ektfl csistivfty 01 nir ined
p.rtáculates kaving thsee sps, coii inuous feed fturu& s ii 6
peecent wstei vapot.
I
?EMPER*TU (F)
3-9
-------
flow characterisitcs of collected particulate are generally more favorable;
however, greater plate surface and volume are required and materials of
construction are more critical.
Velocity - The performance standard has been achieved with space velocities
of three to five feet per second through the precipitator. Greater velocities
would be expected to cause more fly ash reentrainment and resultant higher
particulate releases. At lower velocities, greater collection efficiencies
are possible but it is sometimes difficult to obtain uniform flow across the
precipitator.
Collection Surface - Tests of existing units indicate that a projected
collection surface area of at least 150 square feet per 1000 acfm is re-
quired to meet the performance standard. Such plate area is considered
acceptable only where all other parameters are optimum.
Electrode areas of precipitators at European incinerators are difficult to
ascertain, since this is usually treated as proprietary information. One
of the best controlled plants however, is known to utilize approximately
230 square feet of projected collection surface area per 1000 ACFM.
EPA test data on two European installations show lower particulate emission
levels than U.S. plants. European test results on several installations
indicate the same or significantly lower particulate emissions than these
EPA tests. The European test methods are not entirely relatable to EPA
test results.
\/ v.y little visible emissions are reported at the well controlled European
incinerators compared to significant visible plumes at United States plants.
3-10
-------
Limited observations show less than ten percent opacity from the European
units for extended periods. Some observations of no visible emissions have
also been recorded.
3.2.2 Fabric Filters - Baghouses or fabric filters have found only limited
service to date for the control of particulates from municipal incineration.
The only operating incinerator baghouses are in Switzerland. Successful pilot
plant investigation were carried out as early as 1959 by the City of Pasadena
(California) but the first full-scale United States baghouse is still
under construction in Erie County (New York State).
Experience with industrial process applications would indicate that
fabric filters are adequate to meet particulate emissions levels consistent
with the performance standards. The principal question of their applic-
ability concerns fabric durability under the heat and corrosive chemicals
that are encountered at municipal incinerators. If fabrics can be shown
to provide reasonable bag life, baghouses should be quite acceptable means
of meeting the performance standards.
A pilot plant baghouse was installed adjacent to the municipal incinerator
in Pasadena, California in 1959. Test data obtained there, represent the
only known information on actual baghouse operation, at a municipal incin-
erator in the United States.
The Pasadena pilot plant consisted of a single glass fiber bag treated
with silicone. A sidestream of gas from the incinerator was cooled to 400°F
3-il
-------
and drawn though the bag at about 200 SCFM in reverse flow. The filter
velocity was 4 feet per minute.
The bag was cleaned every half hour by deflating with reverse flow for
two minutes. Maximum pressure drop was found to be from 4 to 6 inches
of water.
Incinerator gas with a dust loading of 0.48 gr/scf was used to test the
pilot plant. Loading of the outlet gas was 0.011 gr/scf, representing an
overall collection efficiency of 98 percent. There were reported to be
no visible emissions.
The pilot plant was operated for a year, then shut down. The single bag
was still serviceable. Operating temperature required constant control
at 500°F. Above 500 0 F the silicone bag covering would rapidly deteriorate;
at low temperatures, condensation on the bag would lead to blinding and
rupture during cleaning.
A second pilot plant baghouse is currently being constructed. This unit
will be installed on a 75 TPD municipal incinerator in Buffalo, New York,
and is designed to handle 50,000 ACFM.
This baghouse is designed to operate at 450—500°F. Bags are made of glass,
treated with silicone. The filter ratio is 2 feet per minute. Maximum pressure
drop is expected to be 5 1/2 inches of water.
3-12
-------
Two municipal incinerators in Switzerland use fabric filters for air
pollution control. 22 One is a small municipal incinerator (36 tons per
day) In Saas Fee 1 Switzerland. It has been in operation since December,
1967. A second larger baghouse-equipped plant (2-100 tons per day furnaces)
is being constructed in Neuchatel, Switzerland, and is expected to be in
operation by the end of 1971. The baghouse on the Neuchatel plant is
a scale-up of the baghouse at Saas Fee.
Both plants use silicone treated glass fiber bags at a filter velocity
of 2.5 feet per minute. Maximum design pressure drop is six inches of
water. At the Saas Fee plant 1 the baghouse temperature is 525°F and
operating pressure drop is four inches of water. A bag life of three
years was achieved. European tests on the Saas Fee plant showed a particulate
emission level of 0.04 gr/scf dry at 12 percent CO 2 . Observations of no
visible emissions have been made.
3.2.3 Scrubbers
Scrubbers used for particulate control have a wide variety of desiqns. 10
The more simple designs do not provide adequate collection efficiency to
meet this performance standard. Certain other designs should be acceptable.
Experience with high energy scrubbers for air pollution control from power
plants, indicate they could easily meet the performance standard.
Practically all scrubbers installed on municipal incinerators in the United
States are of a low energy design. Available test data indicate that these
installations would not meet the performance standard. One installation
3—13
-------
of a higher energy venturi scrubber is in operation in New York City.
Results of EPA tests are not available at this time, however the manu-
facturer has guaranteed an emission level consistent with the performance
standard. This installation is designed to handle about 150,000 ACFM
at 1500 0 F, with a pressure drop of 12 inches of water.
Marble bed scrubbers have achieved greater than 99 percent particulate re-
moval efficiencies (using ASME test methods) on power plant effluents.
These results were achieved on a one stage full scale unit and a two
stage pilot unit. The scrubbers operated at six inches of water pressure
drop for each stage. Although this type of scrubber has not been tested
on municipal incinerators, it shows some promise.
High efficiency scrubbers develop dense steam plumes. This factor should
be taken into account when considering the installation of scrubbers. If
the plant is located within sight of a residential area, many complaints
can be anticipated.
Scrubbers present a water disposal problem that must be considered. The
comon alternatives are discharging the water to the sewer, or recycling
through chemical treatment and/or settling ponds. Whatever approach is
planned, the total effect on the environment should be considered.
3-14
-------
3.3 Performance Data
As part of its program to develop the performance standard, EPA obtained
test data on four of the best controlled municipal incinerators in
Europe and the United States. All four plants employed electrostatic
precipitators. Testing was done with the EPA sampling train using
EPA test procedures.
The plants tested are described below:
Plant A : United States plant with one refractory furnace charging
300 TPD of municipal refuse. Electrostatic precipitator.
Plant B : United States plant with four water-wall furnaces, each
charging 400 TPD municipal refuse. Electrostatic
precipitator.
Plant C : European plant with two water-wall furnaces, each charging
220 TPD municipal refuse. Electrostatic precipitator.
Plant D : European plant with two water-wall furnaces, each charging
400 TPD municipal refuse. Electrostatic precipitator.
Three test runs were made at each plant. Precipitator inlet and outlet
streams were measured simultaneously during each run (except for Run 2
at Plant A where the inlet was not measured). Run 1 at Plant C was
discarded, the relatively high result being attributed to upset conditions
at the plant.
3-15
-------
Test results are plotted in Figure 3-2. Outlet loadings for all
four plants average less than 0.1 grain per scf at 12 percent CO 2 .
Collection efficiencies, calculated from the average values for
inlet and outlet streams, are indicated in the figure.
- 1
-------
94.7
n
82.4
ft
/‘ o11ection Efficiency
jj Hiqhest Test
p_i
4
95.9
p
Average
0.10
0.08
0.06
0.04
0.02
—
Lowest Test
c+.J
cD
C-)
C 4
4- )
to
-D
E
4.)
to
0
U.
C-)
1I )
‘I )
•1
(0
KEY
99.0
I=1
A
B C D
FIGURE 3-2 Measured Particulate Loadin9s at Four Well Controlled Municipal Incinerators
-------
4.0 CONTROL COSTS
Information on the cost of incinerators and control equipment is
included in the cited Little study. Reported costs are based on
extensive review of manufacturers quotes and adjusted to Boston,
Massachusetts, 1969. Accuracy of the costs is estimated by Little
to be ± 20 percent.
Generalized cost curves were prepared by Little for plants and
control equipment of several designs. Both installed costs and
annual operating costs are given. Installed plant costs include
the incinerator, excavation, foundations, dump pits, buildings,
and access roads. Annual operating costs include amortization,
interest, utilities, maintenance, and wages.
Control equipment costs are given in dollars per ACFM as a function
of flue gas rate in ACFM. The relationship between flue gas rate
and refuse charging rate depends on refuse composition, excess air,
and the amount of cooling water evaporated. Conversion factors,
based on average municipal refuse composition, are given in Table
4-1.
For illustration, consider a refractory furnace designed for 150
percent excess air and water spray cooling to 500 0 F. The flue gas
rate, as found from the table, is about 450 ACFM for each ton of
refuse charged in a 24-hour day.
4-1
-------
TA8LE 1 ‘1— 4
EFFECT OF SPRAY TOWER WATER EVAPORATION ON FLUE GAS PROP RTIES 4
Combuition A,, ( sapolsuon Rats Poundi ol Watur Ps, Pound o4 Rsfuw
2
r 3050 2794 1736 12R6
C) hrrssAii c 514 481 446 404 ( 60 1 (’
(321 ‘ ,‘fls rrt,s. V 100 93 87 78 10
( 145 162 172 Il ’ ) 181 I :
I 2690 2060 1574 1178 854 584
75 .E ,gAu C 551 512 471 475 318
401 li ,.’lh ,p(. wI V 100 93 85 77
C) 139 156 167 174 179 I*fl
1 2402 1682 1430 1068 800 54K
50 Fi.c, ss Au C 59’ 537 490 445 398 .141
(481 lb lii ‘ufu ei V 100 92 84
0 133 151 162 169 17 °i 17 i
1 2(68 1700 1322 (016 746 5)?
F5 E.i. ss Ar C 608 561 513 167 415
(562 (t it ivtiiseI V 100 92 84 77 68 5(1
0 129 147 158 165 (7 ! 175
T 1970 1574 1232 944 7(0 494
100iEl, u Asf C 631 586 535 435 (83
(6 42 lb ftirptiicp ( V 100 93 85 77 69 6!
1) 174 143 154 152 161
1 1808 1448 1142 890 656 476
1750 I i ,rss Air C 653 604 552 503 448 40 ?
Il 27 lh.lh tultts,l V 100 92 64 77 6 6 6)
C) 171 140 151 159 166 IGq
1 1682 1358 (070 836 638 440
150 F Ar C 678 627 lii 520 471 417
CS 0 2 lh’lh.ielus,I V 100 92 84 77 70 6!
o 117 38 148 155 (61 166
1 (556 1798 1016 800 60? 47?
I lb”.fxcCsi Air C 695 645 192 641 486 429
(883 th U, refu e( V 100 93 85 78 70 6?
0 114 133 144 154 160 164
1 1466 1196 962 764 566 404
Air C 719 866 •1 1 580 499 444
1063 lb /lb ref usel V 100 92 95 70 69 62
o 112 131 142 150 157 161
1 1304 1070 872 692 530 (86
250%Esc ess Air C 758 701 648 593 537 483
(11 23 lb/lb ref use( V 100 92 85 78 63 64
0 107 126 138 148 152 158
1 1160 962 800 638 494 350
3000.. E,cr’c Air C 788 732 664 627 57? 508
(1784 lb lb ref usii V 100 93 87 80 73 65
0 103 122 133 142 (49 154
T 1070 890 728 584 458 337
35Ø°C. .,A .. C 831 771 712 655 602 54?
(444 Eli’lFi r 1 . . .t V 100 93 88 79 72 65
D 99 118 130 138 (44 150
d Fs(llanalion 01 Symbols
1 F’it .q i temrieraiu,. I II
C luii1a rate (CFM 1 1cr TP() capdcuiyl
V Ratio ot the actual tli,C gas enlume to sPic volume beta, e watse Ivapofation (as a OlecintI
C) Fluvi as ,ipw point I F l
Pus IVIIIySJS is based on average rsf u composit t —
-------
For furnaces with water walls or convective steam boilers, conversion
factors in the table must be corrected for nonevaporative cooling.
For example, consider a water wall furnace operating at 100 percent
excess air, with gas cooling to 500°F. The conversion factor of 631.
found in the table for no spray water cooling and flue gas at 1970°F,
should be multiplied by (500 + 460)1(1970 + 460) to convert for temper-
ature. The results show that the water wall furnace exhausts 249 ACFM
at 500 0 F for each TPD charged.
4.1 Capital Costs
Installation costs are presented as two separate items. The first is
for equipment to cool exhaust gas to about 500 0 F; the second cost is
for cleaning the gas. Their sum is the total capital cost for control
equipment.
4.1.1 Cooling Equipment
Installed costs for five separate cooling systems are shown in Figure 4-1.
Costs for the convective steam boiler are based on cooling the gas to
600 0 F. Costs for the spray systems are for cooling to 500 0 F.
The convective steam boiler consists of a convection tube waste heat
boiler, and required auxiliary equipment; it is used to generate steam
while cooling the incinerator flue gas. (Credit for the steam is not
included in the cost curves.)
4-3
-------
1 .000
1O,cC”)
- L. 1.
i øtr z_
r Fkh’/ ‘j’.e ACFM
4 •i. CC\ : i:; : v;
IOT.’l. ‘• ST M.L E!) J PY ’ T CCST
4-4
1,:: 1•H • ‘( ()
r m FJfrLiT ’i J. .YLiiHil
- - J1 )‘
H—--±— H—f -±ff-—-22 ”r— Tt±HH H
H 7i j m

•
I_ _ iiiJT ELI 2EE
0
Q
t
C
I,
p .-.
-4 -4-
4 . -L
4
TT
Ai
I -
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1
I Li
________
___ LLtCLIH
(fl Cou”uc St eM €oi’r• 4G ) ‘SIG
( C .‘ tivn Stt’.am Boi r• 2 O PSIC
C n tioninq Tower 3r.ci Fine Sprays
® Sprays
Co t , pray
- ‘p
::

. L.IITIITIZ.J. L
L.. . i .J
-------
4.C
C ç 1 c ty 1 0:l c1m)
: J ff 4 l
AIR POLL.tiTlO\I CONInOL SYS11j S — TOL \t..
2.00
U
I : ,
c . 1.CI.()
.Ci)
11 .70
.co
£50
j.0o
I L)
.40
.30
.20
L() 1”) l( ) 200
4-5.
-------
Conditioning towers with fine sprays are so designed that all cooling
water is evaporated, in order to prevent water disposal problems and
eliminate entrained water in the stack effluent. The cost for just
the fine spray equipment is shown as a separate curve to indicate
costs for converting from a coarse to a fine spray tower.
The coarse spray cost curve is for the usual wet bottom conditioning
tower, using water on a once through basis; if water is recycled,
cost is increased 2-4 times for the required settling pond and chemical
water treatment.
The cost of air dilution equipment is not readily available. On the
basis of a single known large installation using air and water cooling,
the expected installation cost is about $20,000. This includes the fan,
ducts, and air headers.
4.1.2 Gas Cleaning Equipment
The installed costs of four high efficiency control devices are shown
in Figure 4-2 (fabric filter, high energy scrubber, and two precipitators).
4.2 Annual Operating Cost
To determine the annual cost of operating the air pollution control
equipment, the installation cost is amortized, by distributing it evenly
throughout the expected lifetime of the equipment. Additional charges
are made for interest, water, power , and maintenance, to arrive at the
total operating cost. These were computed on the following basis.
4-6
-------
1. Capital charges
Amortization - 6.67 percent per year (15 year life)
Interest - 3.14 percent per year (6 percent bonds retired
over 20 years)
2. Utility Costs
Electricity - 1.5 per kilowatt hour
Water - 30 per 1000 gallons (includes sewer charges)
3. 150 percent excess air.
4. Gas cooling from 1650° to 500°F.
On the above basis, total operating cost was computed for 1, 2, and 3
shift operation. Results for the cooling equipment are shown in Figures
4-3, 4—4, and 4-5; results for the gas cleaning equipment are shown in
Figures 4-6, 4-7, and 4-8.
4.3 Plant Cost
Generalized curves, giving both installation and total operating costs
for entire plants as a function of plant capacity, have also been prepared
by Little. As examples, the cost curves for continuous feed rectangular
and water-wall units are reproduced here. Plant installation costs are
shown in Figures 4-9 and 4-11. Operating costs are presented in Figures
4-10 and 4-12.
Steam credits are not included for the water-wall plants. Steam value
is sensitive to local conditions and depends on market availability, the
need for reliability, and the fraction of steam used by the incinerator.
Estimating the value of steam at $0.4 per 1000 pounds, and assuming
that steam production is 6000 pounds per ton of refuse of which 90 percent
is sold, results in a credit of about $2 per ton of refuse. Annual
4-7
-------
ij i 4—3
4 68
Trr td F1u3 C’a ‘ I w R3te
ACFM
LU [ 3AS CCNL)T ON G-- 1 ’:t AL C PERAT i C CO’ 1
.L .:L ‘ .!.Nr 1 i’ 1 Si t AT .
4 8
I r
4
8
6
‘1
‘ .1
0)
4
0’
2 4 6 $ 1OO,O’Y 2
-------
A
/
7,--
Tr ’r FI’; (3 Flow ibte
ACFM
!::: : ::.
$ I
!
- ... ..r...2 .
. L_ . Li

I I
I I
F 1 _ L _ ;.

_____ H
L21+ t rr H
I I ! 1
—--
-
•1
I ----+—• •- --- --- - I-
4 4 UI - S £ t!- 1iOs 1N ANNU?1’... ).‘ F A ‘ :i
• ‘ .• — .- - , --. -
- -
- 1 1
j41:J : “
1. - t. I___._*_ .

I - t_4 LJ J.
L
-
I__-
0
C)
I
4
2
100,000
8
6
4
2
10,000
8
6
4
2
/
-
‘1
/
z
I
JtiJT
i::IiLLt It
(I ’) C rtv€ction BoiI’ r
( 4r 3prey
( Cc r’e Sr rny
2 hift; (4 i
- - —•1-
t i .-: o 4 (3 1C ),C 0 2 4 t
4-9
-------
2 4 G .100,COO 2
4 (3 (3 1,(Y.O, ’iCO
Tras e nu, Gas Flow Rata
ACFM
: -;c ;: 4 -s r GAS W. L:FflONtNG: A;!NUAI. C,P $ C1
.1.’ - ‘ 1 I/ z _t
. r: r1
— — — __4 — — — —• — — •L_ — — -. —— — —- — :— ¶
- .. j...I...L
100.000
a
r
&
10,OC()
10.000
...L 5 UJ.JJ.
4-10
-------
3t0
Capacity (1O acfm)
IIGURE 4 AIR PULLI’T!ON CONTROL SYSTEMS
ANNUAL OPERATING COSTS, Ifr4CLU
/k iOR’!\ ’ U Awl) TUTE E T
>.
0 .
0
0
0
0
0
c:t
C
0
C,
200
10
10
70
(Jo
50
40
30
20
10
‘3
U
7
(3
4
3
2
1
10 20 30 4050 100 200 300
4-11
-------
1
100
90
70
60
50
40
30
20
c
Pt
3
7
CapacIty (10 ac m)
AIR POLLUTION C ThOL. SY r
.AN? 1UAL OPERATIN( COSI$,
,\ icrr.r r:7 :
4-12
>.
( t-
v ’
0
( )
0
V I
c
‘I
()
C-)
C)
1
10 20 304050 100 2t O 3 (k)
-------
Cap3cety (1& scf f l)
ii —
A POLLUTO J CO1 JTflO .. SYSTEMS
ANNWU. OPEAAT NG COSTS L
/
AT c 4 D ..NT’ <
4.43
100
90
Pu
It . ,)
60
tfl
40
30
20
7
4
3
>.
A.
a
‘it
I:
9
C,)
£
F-
.1,
0
C-)
r.
)
2
10 20 30 40 0 100 200 3(X)
-------
11
FIGURI 17
100 150 200
Furnscs Cpsclty (Tons/24 Hour Dsy/Unft)
AVERAGE INVESTMENT COSTS:
CONTINUOUS FEED SYSTEMS
RECTANGULAR CONSTRUCTION
10000
0000
5000
4000
2000
0
0 50
250
300
4-14
-------
t.
0 100 200 300 400 500 600 700 )0 900 1000
Total Capacity TPD
FIGURE 4 0
TOTAL OPERATING COST VS PLANT CAPACITY FOR
CONTINUOUS FEED, RECTANGULAR CONSTRUCTION UNITS
AND t r!RE
Arthir D liuk Inc
?1 00
19 K)
I
1800
1700
16.00
15 (X)
14.00
- 4 . ...4
.1
.-t -
C
C)
1200
‘•i t-
11.00
- — -I
1
10.00
9.00
--4---
-.4
8.00
7.00
6.00
5.00
4.00
4-15
-------
12
FIGURE 1—/i
ESTIMATED 1969 COST OF INCINERATOR
PLANT WITH SOILERS AND PRECIPITATORS
I
11
10
a
8
7
6
100 200 300
TPO/Furnce
600 600
700
4-16
-------
100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400
tot& Plant Cipicity (tons par day)
FIGURE 1-1c
TOTAL OPERATING COSTS — CONTINUOUS-FEED,
WATER WALL-CONSTRUCTION INCINERATOR
SYSTEMS (Grate Burning, No Steam Credits)
‘ $S .iPrp
4-17
10
9
8
7
6
5
4
C
0
tz
k
0
3
Arthur I) Lttltli.
-------
profit for a 300 TPD plant operating for 250 24-hour days is about
$160,000 or about 27 percent of the total operating cost.
4.4 Use of the Cost Curves
For illustration, costs are computed below for incinerators with
capacities of 100 and 300 TPD. Both rectangular and water—wall
furnaces are considered.
The plantsare assumed to operate three shifts a day, 250 days a
year. The rectangular furnaces are assumed to operate at 150
percent excess air, with evaporative cooling of flue gases to 500 0 F.
The water-wall is designed for 100 percent excess air and no evaporative
cooling. Each plant employs an electrostatic precipitator with design
efficiency of 99 percents
To convert furnace capacity in TPD to flue gas volume in ACFM at 500 0 F,
the factors in Table 4-1 are used. For the rectangular furnace the
factor is about 450. For the water-wall, the factor of 631 given in
the table for no evaporative cooling, must be corrected to account for
convective cooling from 1970 to 500°F. The corrected factor is 249.
The installed costs are worked out in Table 4-2. Costs for the control
equipment (precipitator and water sprays) expressed as a percent of entire
plant cost, decrease with increased furnace capacity. For the rectangular
design, control installations are about 14 percent for the 100 TPD plant,
and about 13.5 percent for the 300 TPD plant. For the water-wall design,
the corresponding pertentages are 9 and 6.
4-18
-------
Table 4-2
Installed Costs
Rectangular Furnace
Water-Wall Furnace
150
percent excess air
100 percent excess air
Capacity, TPD
ACFM
Plant cost, $/TPD
(Fig. 4-9, 11), $
Sprays, $
(Fig. 4-1)
99% ESP, $/ACFM
(Fig. 4-2)
Control Equipment
% of total
100
45,000
10,300
I ,030,000
10,500
3.0
135,000
14
300
135,000
6,500
1 ,950,000
21,000
1.8
243,000
13.5
100
24,900
11,500
I ,150,000
4.2
104,580
9
300
74,700
9,850
2,955 ,000
2.2
164,340
6
4-19
-------
Operating costs are developed in Table 4-3. Percentage cost of the
control equipment for the rectangular design now increases with
increased plant capacity, from about 10.2 (100 TPD) to about 13.0
(300 TPD). Cost data is not available for a water-wall plant of
100 TPD capacity. For the 300 TPD water-wall, control costs amount to
about 3.9 percent of total operating cost.
Table 4-3
Total Operating Costs Including Amortization and Interest
Rectangular Furnace
150% excess air
3 shifts per day
250 days per year
Capacity, TPD
ACFM
Water—Wall Furnace
100% excess air
3 shifts per day
250 days per year
100
45,000
300
135,000
Plant Cost, $/ton
(Fig. 4-10, 12) $/yr
100
24,900
300
74,700
11.4
285,000
6.7
502,500
Sprays, #/yr
(Fig. 4—5)
unaI ai1—
able
II
7.8
585,000
11,000
30,500
99% ESP, $/yr
(Fig. 4-8)
18,000
35,000
13,000
Control Equipment
% of total
23,000
10.2
13.0
unavail-
able
3.9
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Per Capita Cost of Air Pollution Control
The per capita cost of air pollution control is computed by distributing
operating cost of the control equipment evenly among the people served.
Per capita cost varies with incinerator design and capacity, and with
the type of control equipment employed. For the examples developed
above, per capita cost is shown in Table 4-4. These costs assume 5.5
pounds daily refuse per person. As the table shows, per capita cost
is about one dollar or less annually.
Table 4-4
Per Capita Cost of Control
Rectangular Furnace
Water-Wall Furnace
100
300
100
300
days/year
250
250
250
250
25,000
75,000
25,000
75,000
$/yr
29,000
65,500
13,000
23,000
Cost, $/yr
1.16
0.87
0.52
0.31
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5.0 RETROFITTING EXISTING MUNICIPAL INCINERATORS
The standard of performance was developed for new and substantially
modified municipal incinerators. Unless existing plants are modified,
the particulate emission limit does not apply. It is however recognized
that in many areas, State and local agencies will need to consider
emission reductions from plants now In operation. Suggested
approaches are provided. Design features of individual plants will
determine what approach is best to follow.
Control of air pollution at incinerators depends on complete combustion
of refuse, and efficient cleaning of stack gases. Both factors are
important and interrelated. Complete combustion is the best way to
control emissions of many contaminants. Soot, carbon monoxide, and
organic gases are thereby avoided. Combustion can be improved by
furnace modifications that promote turbulence in the bed and the
combustion zones. Bed turbulence increases fly ash entrainment but is
acceptable when combined with efficient particle collection equipment.
Electrostatic precipitators, high energy scrubbers, and fabric filters
provide the highest level of particulate control. Their installation
can be carried out at many existing Incinerators to replace less
satisfactory control equipment.
Precipitators and fabric filters require cooling the flue gases to
about 500°F. Provisions must be made for a spray chamber or air
dilution equipment. Some plants are designed with adequate spray
chambers. Certain scrubbers do not require prior gas cooling, and
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hot furnace gases are ducted directly to the equipment.
Installation of scrubbers or fabric filters increases the pressure
drop between furnace and stack. Also, if air dilution cooling is
employed, flue gas volume increases. As a result, the induced draft
fan may need replacing with a fan of greater capacity. If no fan
exists, one will be required with any high efficiency particulate
collection equipment.
Space limitation is an important consideration in remodeling a plant
that is enclosed or located in a conjested area. Relative space
requirements for control equipment are listed below:
Equipment Type Relative Space Requirement
Baghouse Filter 100
Precipitator 90
Venturi Scrubber 25
For new plants the principal control cost is for installing and operating
the particle collection device. The same should be true for remodeled
plants, unless unusual situations occur.
The costs for installing and operating new control equipment is presented
in Section 4. These costs may be used to estimate remodeling expenses,
giving consideration to possible additional costs arising from such
items as additional land purchase, building modifications, and increased
loading on the draft fan. These additional costs may be a significant
part of the total installation costs.
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6.0 References
1. Black, R. J., et. al. , “The National Solid Waste Survey, an
Interim Report”.
2. “Systems Study of Air Pollution from Municipal Incineration,”
A Report under Contract CPA-22-69-23 to the National Air Pollution
Control Administration by Arthur 0 , Little, Inc., March 1970.
Three volumes.
3. Heaney, F. L., “Furnace Configuration,” In Proceedings; 1964
National Incinerator Conference, New York, May 18-20, 1964
American Society of Mechanical Engineers, pp. 52-7.
4. Stenburg, R. L., et. al., “Field Evaluation of Combustion Air
Effects on Atmospheric Emissions from Municipal Incinerators,
Journal of the Air Pollution Control Association, 12(2), pp.
83-9, February 1962.
5. Walker, A. B. and Schmitz, F. bE., 1 ’Characteristics of Furnace
Emissions from Large, Mechanically-Stoked Municipal Incinerators,’
In Proceedings; 1966 National Incinerator Conference, New York,
May 1-4, 1966, American Society of Mechanical Engineers, pp. 64-73.
6. Kaiser, E. R., “Refuse Composition and Flue-Gas Analysis from
Municipal Incinerators,” In Proceedings; 1964 National Incinerator
Conference, New York, May 18-20, 1964, American Society of
Mechanical Engineers, pp. 35-51.
7. Stephenson, J. W., and A. S. Cafiero, Municipal Incinerator Design
Practices and Trends. In Proceedings: 1966 National Incinerator
Conference, New York, May 14, 1966. American Society Of Mechanical
Engineers, p. 1-38.
8. Conner, W. D., and 3. R. Hodkinson. Optical Proterties and Visual
Effects of Smoke-Stack Plumes. Public Health Service Publication
No. 999—AP-30. Cincinnati, U. S. Department of Health, Education
and Welfare, 1%?, 89 p.
9. U. S. Department of Health, Education and Welfare, Public Health
Service, Division of Air Pollution. Equivalent Opacity—-A Useful
and Effective Concept for Regulating Visible Air Pollution Emissions.
Presented at East-West Gateway Coordinating Council Hearings on the
Proposed Interstate Air Pollution Study Reconinendations, St. Louis,
September 27, 1966, 13 p.
10. Control Techniques for Particulate Air Pollutants . National Air
Pollution Control Administration Publication AP-5l (1969).
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References (continued)
11. White, H. J., llndustrial Electrostatic Precipitation”
Addison-Wesley, Reading, Massachusetts.
12. Ramsdell, R. G, Jr., “Design Criteria for Modern Central
Station Power Plants.” Consolidated Edison Company of
New York, Inc., April 1968.
13. Archbold, M. J., “Combustion Observations and Experience
Resulting from a Precipitator Improvement Pro 9 ram.”
Proc. American Power Conference, Chicago, Illinois, March
1961, Volume 23, pp. 371-390.
14. “Baghouse Cures Stack Effluent,” Power Engineering, May 1961.
15. Kaiser, E. R., “Chemical Analysis of Refuse Components”,
Proc. of 1966 National Incinerator Conference, pp. 84-88, ASME,
New York, 1966.
16. Andritzky, M., Brennstoff-Warme -Kraft, 19(9), 436 (1967).
17. Stern (Ed.), Air Pollution , Volume II, pp. 292—3l2
18. McGraw, J. J. and Duprey, R. L., Compliation of Air Pollutant
Emission Factors (Preliminary Document), Environmental Protection
Agency, Research Triangle Park, North Carolina, April 1971.
19. Anon. “A Rain Fed Incinerator”, America City, 80 (1), 34 (1965).
20. Anon. “Continuous Municipal Incineration Plant”, Steam and
Heating Engineering, 36, 7-13 (March 1967).
21. Anon, “Scrubber Device for Incinerator Site”, Refuse Removal
Journal 10 (4), 49 (1967).
22. Private Conununication with the Amsterdam, Holland Office of
American Air Filter Company, June 1971.
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