special studies for incinerators
FOR THE GOVERNMENT OF THE DISTRICT OF COLUMBIA
U.S. DEPARTMENT OF HEALTH. EDUCATION, AND WELFARE
PUBLIC HEALTH SERVICE
CONSUMER PROTECTION AND ENVIRONMENTAL HEALTH SERVICE
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PUBLIC HEALTH SERVICE PUBLICATION NO. 1748
For sale by the Superintendent of Docum
ents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 75 cents
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foreword
THIS REPORT (SW—Id) was prepared by Day & Zimmermann Associates for the
District of Columbia under partial support of Demonstration Grant No. D01-SW-
00038-01, Solid Wastes Program, Environmental Control Administration, Consumer
Protection and Environmental Health Service, Public Health Service, U.S. Department
of Health, Education, and Welfare.
The report, consisting of six special studies, was prepared as part of the evalua-
tions leading to a design for an incinerator (No. 5) for the District of Columbia.
The text of this report provides a thorough technical discussion of commonly con-
sidered options in incineration. This information should be useful for other com-
munities considering these alternatives.
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preface
AN ESTIMATED 800 MILLION POUNDS of solid wastes of all types are produced in the
United States every day. What to do with these solid wastes, how to dispose of them
without needlessly endangering public health and welfare, and how to recover and
reuse valuable materials now "thrown away" are among the most challenging and
perplexing of current national problems. Because of lack of suitable planning, interest,
and public understanding, these problems have reached such proportions that nation-
wide attention is demanded and action for the development of adequate solutions
must be taken.
Intensified action concerning these problems was made possible by the Solid
Waste Disposal Act, Title II of Public Law 89-272, which was signed by the President
on October 20, 1965. This legislation directs the Secretary of the Department of
Health, Education, and Welfare to initiate, encourage, and support a national
program aimed at discovering and evaluating better methods of coping with the
solid waste problem.
The Secretary is authorized (1) to conduct and support research on the nature
and scope of the problem, on methods of more safely and efficiently collecting and
disposing of solid wastes, and on techniques for recovering from solid wastes poten-
tially valuable materials and energy; (2) to provide training and financial and tech-
nical assistance to local and state agencies so that they can survey their needs in the
solid waste area and plan for the development and staffing of programs capable of
meeting those needs now and in the years to come; (3) to encourage and support
projects that may demonstrate new and improved methods of solid waste collection,
handling, and disposal.
To carry out these responsibilities, the Solid Wastes Program was established.
Among the responsibilities with which the Program is charged is that of providing
grant support for demonstrations relating to the development and application of
new and improved methods of solid waste collection, storage, processing and ultimate
disposal; and also for studies and investigations that may lead to a demonstration of
improved disposal practices, or may provide solutions for regional or national solid
waste disposal problems. Associated with this is the responsibility of collecting
and making available by appropriate means the results of, and other information
pertaining to, such federally supported demonstrations, studies and investigations.
Accordingly this report is published to disseminate as widely as possible the
information and findings of a project that has received grant-support from the Solid
Wastes Program. We hope that the report will provide those working in this field
with useful information that will be of assistance in developing approaches to
the solutions of their solid waste disposal problems.
—RICHARD D. VAUGHAN
Chief, Solid Wastes Program
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contents
STUDY OF MUNICIPAL INCINERATOR EFFLUENT GASES
Abstract 1
Introduction 1
Summary and Recommendations 1
Refuse Composition 3
Determination of Possible Pollution Products 3
Corrosion and Toxicity of Pollutants 8
Effects of Furnace Operation on Pollutants 9
Evaluation of Air Pollution Control Equipment 11
Estimates of Capital and Operating Costs for Air Pollution Control Equip-
ment 16
References 17
Bibliography 19
Appendix A: Tables 10 to 36 21
CONTROL LABORATORY
Abstract 2.9
Introduction 29
Summary and Recommendations 29
Group I: Indicating and Recording Equipment for Incinerator Operation 29
Group II: Physical Laboratory Equipment 30
Group IH: Chemical Laboratory Equipment 33
Group IV: Monitoring Equipment for Test and Development Studies 36
References 37
Bibliography 38
SIZE REDUCTION OF OVERSIZE BURNABLE WASTE
Abstract 39
Introduction 39
Summary and Recommendations 39
Types of Oversize Burnable Waste 40
Disposal Methods 40
Equipment for Shredding 40
Machine Limitations 41
Effects of Shredded Material on Furnace Operations 42
Incinerators for Burning Bulky Objects 42
Equipment for Splitting Tree Stumps 43
Capital and Operating Costs 44
References 46
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SIZE REDUCTION OF BULKY METAL OBJECTS BY
COMPRESSION PRESSES
Abstract 47
Introduction 47
Summary and Recommendations 47
Source and Quantity of Bulky Metal Objects 48
Disposal Methods 48
Compression Equipment 48
Proposed Equipment Installations 49
Estimated Capital Investment Costs 52
Estimated Operating Costs 52
Table of Annual Operating Costs 53
Appendix B: Representative list of manufacturers of Hydraulic Press Equip-
ment 53
HEAT RECOVERY
Abstract 55
Introduction 55
Summary and Recommendations 55
Refuse Composition 56
Effect of Incinerator Operation on Boiler Performance and Design 57
Effect of Boiler Opeiation on Incinerator Performance and Design 59
Factors Affecting Steam Generating Capacity 60
Effect of Boiler Installation on Air Pollution Contiol Equipment 62
Description of Equipment Arrangements 63
Estimated Capital and Annual Operating Costs 68
Value of Steam for Sale 68
Sale of Steam at Proposed Plantsite 70
Appendix C: Typical Municipal Refuse Ultimate Analyses 71
Appendix D: History of East Coast Incinerator-Boiler Installations 72
References. 73
CAN-METAL RECOVERY
Abstract 75
Introduction 75
Summary and Recommendations 75
Source and Quantity of Metal Waste 75
Disposal of Recovered Metal 76
Available Metal Recovery Methods 77
Capital Investment and Operating Costs 78
Appendix E: Incinerators Practicing Metal Salvage 78
Appendix F: Private Firms in the Scrap Metal Industry 80
References
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study
OF MUNICIPAL INCINERATOR EFFLUENT GASES
ABSTRACT
THE SCOPE of this study includes: an estimation of
the chemical constituents of municipal incinerator
effluent gases; the potential air pollution hazard of-
such chemicals; and the evaluation of various abate-
ment devices applicable to the gas stream leaving the
furnaces of a proposed 800-tons-per-day incinerator
plant.
The effluent stream was found to contain inorganic
and organic substances in the form of both gases
and particulates. Some of these constituents in the
effluent stream were found to be both toxic and cor-
rosive when present in appreciable amounts.
Electrostatic precipitators and high energy scrubbers
are two types of pollution control equipment appli-
cable to this particular plant. Electrostatic precipi-
tators preceded by mechanical collectors are recom-
mended for the air pollution control equipment. The
use of high energy scrubbers is considered acceptable
from a performance standpoint, but esthetic objections
to the vapor plume and probable thermal pollution
of the water source rule out this application at the
District of Columbia location.
INTRODUCTION
THE PURPOSE of this study was as follows: to
estimate the types of air pollutants contributed by
the gaseous stack effluents from municipal incinera-
tors; to investigate the effects of various furnace
operating variables on the emission of air pollutants;
to evaluate the performance of various types of air
pollution abatement devices; to develop capital and
operating cost estimates for acceptable types of air
pollution control equipment; to make recommenda-
tions for equipment to be installed at the proposed
Incinerator No. 5 in Washington, D.C.
In making this study, it was first necessary to
determine the amount and type of constituents in
the effluent gases from the incinerator which could
contribute to air pollution. In this determination,
two approaches were used: one was analytical, and
and the other was empirical, by review of actual
test data.
The effects of such furnace variables—as temperature,
amount of excess air, fuel bed agitation and incom-
plete combustion—on the generation of contaminants
were reviewed.
After determination of the probable types and
quantities of pollutants emitted from municipal in-
cinerator furnaces, the effectiveness of various types
of pollution control equipment was reviewed. An
evaluation was made of both performance and possible
operating problems, including the effect of various
types of furnaces and furnace boiler combinations on
equipment size and performance. Capital and operating
cost estimates were developed for the types of equip-
ment that would meet the requirements of the Federal
Air Pollution Code. Conclusions and recommendations
were developed based on analysis of the data obtained
during this study.
SUMMARY AND RECOMMENDATIONS
The anticipated chemical pollutants in a municipal
incinerator effluent gas may be grouped into two
general catagories: inorganic gases and particulate
matter; and, organic gases and particulate matter.
Inorganic Gases.—The inorganic gases consist pri-
marily of oxides of sulfur, oxides of nitrogen, and
ammonia. The inorganic particulates consist primarily
of the oxides of such metals as aluminum, silicon,
potassium, calcium, iron, titanium, zinc, sodium, and
magnesium. Formation of complex oxides of aluminum
and silicon is also possible.
Organic Gases.—The organic gases and particulate
matter consist primarily of fatty acids, esters, alde-
hydes, hydrocarbons and oxides of carbon. Most are
present as gases although the fatty acids may also be
present as particulates.
289-620 O—68-
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DAY & ZIMMERMANN
In general, large percentages (up to 50'percent) of
the particulate matter were found to be of a combus-
tible nature. Of this combustible particluate, quanti-
ties up to 50 percent were found to be acetone-soluble.
Corrosion problems can be caused by the oxides of
sulfur, nitrogen, and carbon. The oxides of such
metals as sodium, potassium, iron, and zinc may also
contribute to corrosion because of either the strong
acidic or basic characteristics exhibited when such
oxides are hydrolyzed. Products of combustion of
halogenated compounds have been shown to be
highly corrosive in minute quantities.
Toxic effects can result from the presence of the
following pollutants if present in significant amounts:
oxides of nitrogen; ammonia and its salts such as
ammonium sulfate; aldehydes; esters; carbon monoxide
and carbon dioxide; oxides of silicon, sodium, potas-
sium and magnesium; polynuclear hydrocarbons; and
phosgene or toluene diisocyanate.
For a given refuse composition, the quantity of
particulates appears to increase with increased grate
action and increased underfire airflow and to decrease
with improved combustion.
The distribution of particle size appears to vary
with combustion efficiency, underfire airflow and
character of refuse. Furnaces operated in excess of
design capacity show a larger weight of particulate
matter per pound of flue gas. Size analysis of this
particulate indicated low percentages of particulates
smaller than 10 microns in size. Furnaces operated
with low underfire air rates and at less than rated
capacity show large percentages of particulates smaller
than 10 microns in size.
To evaluate air pollution control equipment, a
particulate loading of 3 pounds per thousand pounds
of dry flue gas was selected for design purposes. The
particulate matter was further stipulated to contain
30 percent by weight of particles smaller than 30
microns in size.
To obtain a dust loading in the final effluent gas
which will meet the Federal Air Pollution Code
requirements of less than 0.2 grain of particulate
matter per standard cubic foot of dry flue gas corrected
to 12 percent carbon dioxide, particulate control
equipment having an overall efficiency of not less
than 94 percent will be required. This is based upon
an approximate CO2 content in the flue gas of 6
percent at a 200 percent excess air condition.
The results of the study indicated that two types
of particulate control equipment will meet the re-
quirements of the Federal Air Pollution Code.
These are the flooded plate or venturi scrubber (high
energy scrubbers) and the electrostatic precipitator
preceded by a mechanical collector.
Venturi and flooded plate scrubbers exhibit rel-
atively high efficiency of particulate removal and
can absorb some of the gaseous contaminants, such
as ammonia (NH3) and sulfur trioxide (SO3).
They have the disadvantages of high water consump-
tion, high power costs, the presence of a plume of
"steam" (condensed water vapor) at the stack
discharge, and the problem of treating the effluent
water for pH control and removal of fly ash. Con-
struction materials must be carefully selected for
corrosion protection.
Electrostatic precipitators have very high effi-
ciency on small particles and the ability to remove
in the dry state the small particulate matter in the
gas stream. They have the disadvantages of large
space requirements, large capital costs, and a
critical operating temperature range; and, in addi-
tion, there is at present a lack of operating experience
with municipal refuse fly ash from U.S. cities. Some
operating difficulties with electrostatic precipitators
are anticipated due to possible fouling with fatty
acid particulates and cementations fly ash. Corrosion
of metallic surfaces can also occur when the pre-
cipitators are allowed to operate below the dew
point of the incoming gas stream. Installation of
mechanical cyclone collectors in the gas stream ahead
of the electrostatic precipitators, to remove large
particulate matter, is recommended.
The estimated capital and operating costs for the
two basic systems for an installation at the proposed
District of Columbia Incinerator No. 5 (800 tons/day)
may be summarized as follows:
TABLE 1
ESTIMATED CAPITAL AND OPERATING COSTS FOR TWO INCINERATOR
SYSTEMS
Type
Electrostatic precipitator with mechanical
High energy scrubber
Capital
costs
$2, 409, 200
1, 838, 600
Annual
operating
cost
$512, 500
401, 000
The capital costs include all portions of the plant
and equipment which vary with the type of equip-
ment installed. They do not represent the cost of
adding the equipment to a specific plant design.
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special studies for incinerators
TABLE 2
TYPICAL REFUSE ANALYSIS '
Refuse
Percent total
refuse (by
veight; dry
basis)
DETERMINATION OF POSSIBLE POLLUTION PRODUCTS
Two approaches were used in the determination of
the possible pollution products that would be present
in the gaseous effluent from municipal incinerators.
One approach was to review the data and results
of the actual sampling and chemical composition of
the refuse. In addition to published data, some un-
We recommend that the electrostatic precipitator
unit be installed at Incinerator No. 5, since the plume
of steam from the high energy scrubber would be =_=___=_
objectionable at this location. Also temperature con-
ditions in the Anacostia River rule against its use as
a water supply. The high energy scrubber installation
presents a slightly more economical installation, but
the additional cost of plume elimination and the
river water conditions offset this advantage. Plants and grass:
We also recommend further investigation to eval- Evergret
... ° Flower garden plants 1.68
uate the anticipated polynuclear hydrocarbons, com- Lawn grass green x.68
bustion products from halogenated hydrocarbons, and Ripe tree leaves 2.52
phosgene or toluene diisocyanate that could be present
in the effluent gases from municipal incinerators since Total> plants and grass' •
such materials exhibit highly toxic and corrosive n. , , , , „
. o j Ulrt ancj vacuum cleaner catch 2.52
characteristics when present in minute quantities. Plastics 3.50
Paints, oils and removers 0. 84
REFUSE COMPOSITION Glass and ceramics 8.50
Leather 0.42
To determine the anticipated pollutants from Wood and balsim spruce 2.52
incineration of municipal refuse, the composition Rubber o. 42
of the refuse must be established. Municipal refuse is
j r . j i • Paper products:
composed of many complex compounds, each varying N£ ers 10 33
in amount from small traces to large percentages Brown papers 6.12
of the total weight of refuse charged. Corrugated boxes 23.92
A typical municipal refuse contains many major Plastic coated papers 0.84
classifications of waste materials. Table 2 is a typical Waxed milk cartons °'84
, ., ,. ,., j • . • Tissue PaPer 2-18
refuse material analysis which was used in this Tnk mai[ 3 03
study to determine the combustion products in the Paper food cartons 1.27
gas leaving the furnace. The percentage of certain Magazine paper 7.48
items can vary seasonally, for example, the percent of
lawn grass could range from 0 to approximately Total, paper products 56.01
32 percent depending upon the time of year. The Foodwastes:
figure of 1.68 percent was used as a typical average Vegetable food wastes 2.52
on an annual basis. Meat scraps (cooked) 2.52
As may be seen from table 2, major classifications Fned fats 2-52
have been grouped according to chemical composition. ltrus rm s an sec s
Each of these groups has been further subdivided Total, food wastes 9.24
into individual chemical constituents as shown in
tables 10 through 19 in the appendix. Rags 0.84
The important chemical constituents of the refuse Metals 7-53
and the source of such items were determined and Miscellaneous 0.10
the results summarized as indicated in tables 3 and 4. Total 100.00
1 Abstracted from study by Kaiser CO-
published information was made available for this
study. The second approach was a theoretical one
in that the effluent constituents were determined by
estimating the combustion products based on the
chemical composition of the refuse. This second
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DAY 8c ZIMMERMANN
TABLE 3
REFUSE ANALYSIS : SUMMARY OP INORGANIC CONSTITUENTS
Item
Sulfur oxides, SC>2, SOs
Silicon dioxide, SiO2 . . . .
Magnesium oxide, MgO. ... . .
Chromium oxide, G^Os
Sodium oxide Na2O
Boron oxide f^Os ... ...
Lead oxide PbO
Tin oxides SnC>2, SnO
Manganese oxide, MnO
Cadmium oxide CdO . ... ....
Zinc oxide ZnO . ...
Fluorides F% (acid and salts)
Sources
Glass and
ceramics
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Dirt
X
X
X
X
X
X
X
X
X
Metals
X
X
X
X
X
X
X
X
X
X
X
Wood
products
X
X
X
Food
wastes
X
X
X
Plastics
X
X
X
X
approach is essentially a qualitative one, of primary
importance in determining the chemical composition
of possible pollutants, but not necessarily the
quantity.
In the analysis and discussion that follow, the main
emphasis is placed on the following: The kinds and
types of substances which are in the effluent stream;
the source of such materials (type of refuse); the
mechanism by which these substances could evolve
during the incineration process; and, the data, pub-
blished or unpublished, substantiating the existence
of these substances in the gaseous effluent.
The anticipated chemicals in the incinerator flue
gas can be grouped into two major categories: organic
and inorganic substances, each of which can exist as
gases or particulates. Data reviewed indicates that a
large percentage of the partiuclate matter (up to 50
percent) was found to be combustible. Of this com-
bustible fraction, up to 50 percent was soluble in
acetone (2).
Organic Substances
The organic substances in incinerator flue gas may
consist of organic acids (fatty acids), esters, aldehydes,
ketones, alcohols, hydrocarbons, polynuclear hydro-
carbons, halogenated hydrocarbons, and oxides of
carbon (CO, CO2). Fatty acids may exist in both the
gas and particulate phase, but all the other organic
substances probably exist in the gaseous state.
Organic Acids.—The organic acids normally en-
countered are classified as fatty acids. The important
ones are formic acid, acetic acid, palmitic acid, stearic
acid, oleic acid, and palmitoleic acid. These are found
in the form of fats and esters of the following refuse:
wood and balsam spruce; paper products; food wastes;
and, plants and grass.
Table 19 in appendix A lists the above acids and
additional data on their chemical structure and
occurrence.
Fatty acids can be produced from the breakdown
of the above types of refuse due to the high temper-
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special studies for incinerators
TABLE 4
REFUSE ANALYSIS: SUMMARY OF ORGANIC CONSTITUENTS
Item
Carbohydrates
Lipids (fats)
Acrylonitrile-butadiene-styrene polymers
Cellulose acetate
Cellulose acetate butyrate
Cellulose nitrate
Melamine formaldehyde ....
Polyethylene
Poly vinyl dichloride
Urea formaldehyde
Urethane
Polymethyl methacrylate
Polypropylene
Polystyrene
Polyvinyl acetate
Polyvinyl chloride
Halogenated hydrocarbons
Polynuclear hydrocarbons
Wood
Wood
products
Food
wastes
Sources
Plants
and grass
Plastics
V
Rubber
Y
Pres-
surized
cans
x
atures in the incinerator furnace. The most important
type of reaction that probably occurs is decarboxyl-
ation. The mechanism of this type of reaction is
illustrated in table 20 in appendix A.
Jacobs, Braverman, Hochheiser and Ettinger listed
the organic acid content of incinerator flue gas as 25
to 133 p.p.m. based on analysis of actual samples (3).
The Western Oil and Gas Association estimated the
amount of organic acids as 0.6 pounds per ton of
refuse burned (4*).
It was mentioned previously that significant
amounts of combustible particulates in the flue gas
are acetone soluble. Since fatty acids are soluble in
acetone (5) this tends to further substantiate the
existence of such compounds in the flue gas.
Esters.—Methyl acetate, ethyl acetate, and ethyl
stearate are typical esters which could be contained
in the composition of the refuse. These are found in
the lipid portion of wood, wood products, and food
food wastes. In the thermal breakdown of such
refuse, an ester would be liberated. The majority of
these esters, however, will further decompose into
fatty acids (5) as previously discussed.
Jacobs and coworkers list the ester content of
incinerator flue gas as 5 to 137 p.p.m. based on
chemical analysis of actual samples (3).
Aldehydes.—Acetaldehyde and formaldehyde are
typical of the types of aldehydes which are most
likely present in incinerator flue gas. Aldehydes can
be formed from the thermal decomposition of such
plastics as melamine formaldehyde and urea formal-
dehyde and thermal decomposition of polyhydroxy
aldehydes (.6-8). Polyhydroxy aldehydes are one of
the forms of carbohydrates which are present in
such refuse as wood, wood products, food waste,
plants, and grass.
Jacobs and coauthors listed the amount of alde-
hydes as 10.8 to 82 p.p.m. based on actual sampling
and analysis of incinerator flue gas samples (3). The
Western Oil and Gas Association estimated the
amounts of aldehydes to be 1.1 pounds per ton of
refuse burned (4~).
Ketones.—Ketones are present in the form of poly-
hydroxy ketones in carbohydrates (8~). The poly-
hydroxy ketones will be decomposed by the heat of
incineration and could liberate ketones. It is believed
that these ketones would readily burn to carbon
dioxide and water vapor. Review of published data
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DAY & ZIMMERMANN
did not disclose any reference to any actual or antici-
pated amounts of ketones in the gaseous effluent
from the incinerator.
Alcohols.—Alcohols can appear as the decomposition
products of carbohydrates. However, it is anticipated
that the alcohol would readily burn to carbon dioxide
and water in the presence of excess air (
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special studies for incinerators
TABLE 5
ANTICIPATED ORGANIC SUBSTANCES IN THE INCINERATOR EFFLUENT GAS
Kind
Organic acids:
Formic
Acetic
Palmitic
Stearic
Oleic
Palmirnlcir
Esters :
Methyl acetate
Ethyl acetate
Ethyl stearate
Aldehydes :
Acetaldehyde
Formaldehyde
CO
COj
Polynuclear hydrocarbons ....
Halogenated hydrocarbons A
Phosgene .
Wood, wood
products,
plants and
grass, food
waste
Source
Rubber
Plastics
Vary with
excess air
Amounts reported
?S rn 1 "\"\ n fi m C^
5 to 137 p p m 0)
1.7 to 3.9xlO~4 00-
35 to 400 p p.m (3)
1 Also from pressurized can chemicals.
as plastics, wood, wood products, food wastes, grass
and plants, contains nitrogen, in one form or another,
as one of the constituents. Such refuse when subjected
to the heat in the incinerator furnace can liberate
nitrogen which can then be oxidized. There are several
oxides of nitrogen, the most common of which are
nitrogen dioxide (TS[O2), nitric oxide (NO), and
nitrogen trioxide (N2O8). It is anticipated that NO2
will be the principal oxide present in the flue gas.
Nitric oxide (NO) is readily oxidized to NO2 and
nitrogen trioxide (N2O3) readily decomposes to NO
which will oxidize as stated to NO2 (J2).
Jacobs and coworkers listed the amount of NO2 in
the incinerator flue gas as 0.15 to 1.5 p.p.m. based
on results of actual sampling and analysis (3). The
Western Oil and Gas Association listed the
estimated quantity of NOX (tested as NO2) as 2.1
pounds per ton of refuse burned (f).
Sulfur Oxides (SO2, SO3).—Sulfur is present in pro-
teins as the chemical bond in the helical structure
and also in the functional groups of certain proteins.
Sulfur can be liberated upon degradation of the protein
molecules due to the heat in the incinerator furnace.
The sulfur would be readily oxidized to sulfur dioxide
(SO2). Some of SO2 thus formed could be further oxi-
dized to sulfur trioxide (SO3) as follows (11): (a)
Oxidation of SO2 by oxygen molecules in the flame;
(b) catalytic oxidation of SO2 at surfaces in the post
flame region.
The above reactions are aided by the presence of
nitric oxide (NO) and carbon monoxide (CO) and
are not'significantly affected by the presence of large
amounts of carbon dioxide (CO2) (if).
Jacobs and coauthors (3) listed the amount of SO2
in the incinerator flue gas as 0.25 to 1.2 p.p.m. based
on results of actual sampling and analysis. The
Western Oil and Gas Association (f) listed the esti-
mated quantity of SOX (as SO2) as 1.9 pounds per
ton of refuse burned.
Sulfur oxides have also been reported in fly ash.
Kaiser reported the amount of SOX in fly ash as 3.0
percent by weight collected and 8.0 percent by
weight in the emitted ash (Iff).
Chlorine (C12), Fluorine (F2) and Hydrogen Cyanide
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DAY & ZIMMERMANN
(HCN).—The sources of these inorganic gases are
as follows: Chlorine (C12): vinyl plastics and pro-
pellants in pressurized cans; Fluorine (F2): Teflon®
plastics and propellants in pressurized cans; and
hydrogen cyanide (HCN): methacrylate plastics. It
is anticipated that these substances would be liberated
when the above materials are decomposed due to the
high temperatures in the incinerator furnace (d, 7).
Since chlorine and fluorine have a great affinity
for hydrogen they will probably be present as hydro-
gen chloride (HC1) and hydrogen fluoride (HF) in
the flue gas.
There were no published data discovered reporting
any test results or estimated amounts of these sub-
stances in incinerator flue gas.
SUMMARY OF INORGANIC GASES
Table 6 presents a summary of the anticipated
gases in the incinerator flue gas, together with
reference to their source (refuse) and amounts
(published and unpublished data).
CORROSION AND TOXICITY OF POLLUTANTS
The corrosive and toxic properties of the anticipated
chemical pollutants were reviewed by each major
grouping, i.e., organic substances, inorganic partic-
ulates, and inorganic gases, and are discussed below.
It should be noted that the quantities of pollutants
reported in the flue gases will be significantly reduced
at ground levels by dispersion from the top of chim-
neys or stacks at the incinerator plant.
Organic Substances
Table 29 in the appendix summarizes the organic
pollutants with their toxic and corrosive character-
istics. Tables 30 and 31 in appendix A contain ad-
ditional data on halogenated hydrocarbons and
polynuclear hydrocarbons.
From a review and analysis of the data, it appears
that organic acids, aldehydes, and esters do not pre-
sent any corrosion problems. Some aldehydes and
esters exhibit toxic properties and could present a
toxic hazard if present in considerable quantities.
The organic acids do not represent any health hazard.
The oxides of carbon (CO and CO2) do not normally
present toxic and corrosive hazards. Carbon monoxide,
while highly toxic, would only be present in trace
amounts due to the large excess air used in incinerator
operation. Carbon dioxide is dangerous in high con-
centration but again the high levels of excess air
should result in adequate dilution. Corrosive con-
ditions could develop if appreciable amounts of CC>2
are absorbed in water. However, the high temper-
TABLE 6
ANTICIPATED INORGANIC GASES IN THE INCINERATOR FLUE GAS
Chemical
NH3
NO2 (nitrogen dioxide)
SO2 (sulfur dioxide) and SO3 (sulfur trioxide) .
C12, F2, HCN
Sourc
Wood, wood
products,
plants and
grass, food
waste
X
X
e
Plastics
X
X
Vary with
excess air
X
Amount
0 44-10 p p.m. (3)
0.3 Ibs./ton refuse burned (4~).
0.15-1.5 p.p.m. (3).
0.2-0.33 lbs./l,000 Ibs. dry flue gas (9).
2.1 Ibs./ton refuse burned (4).
SOs-3 and 8 percent by weight collected and emitted
respectively
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special studies for incinerators
atures in the incinerator system decrease the solubility
or CO2 in water significantly.
The substances liberated when incinerating pres-
surized cans present both a toxic and corrosive hazard.
Kama and Curley stated that the cause of such hazards
from the halogenated hydrocarbons in the cans is not
the chemicals per se, but the decomposition products
which are highly corrosive and toxic compounds,
primarily hydrogen chloride (HC1) and hydrogen
fluoride (HF) (12).
The combustion products from the incineration of
rubber products exhibit highly toxic properties as
shown in table 31 03).
The thermal decomposition of polyurethane type
plastics could constitute a toxic hazard due to the
liberation of phosgene and/or toluene diisocyanate.
Phosgene as noted on table 29 is highly toxic and tol-
uene diisocyanate exhibits similar properties as may
be illustrated in published references (14, 15~).
Inorganic Particulates
Table 32 (appendix A) summarizes the inorganic par-
ticulates with their toxic and corrosive characteristics.
From the data presented, substances such as SiO2,
Na2O, K2O, and MgO could represent a potential
health hazard because of their high toxic level if
generated in significant quantities without adequate
dispersion. Na2O, K2O, Fe2O3, and ZnO could be a
cause of corrosion because of either their strong
basic or acidic characteristics. There is also a pos-
sibility of the formation of complex oxides of alumi-
num and silica, which can be highly abrasive.
Inorganic Gases
Table 33 (appendix A) summarizes the inorganic
gases with their toxic and corrosive characteristics.
Corrosion experienced in combustion processes in those
zones where the combustion products have been
cooled has been related to the sulfur trioxide (SO3)
of the flue gas (1Z). Sulfur trioxide has been shown
to be generated, in significantly large amounts, from
the oxidation of SO2 in the presence of carbon mo-
noxide (CO) and nitric oxide (NO).
Sulfur oxides (SO2, SO3), ammonia (NH3), and
nitrogen dioxide (NO2) all could be a potential toxic
hazard because of their high index of toxicity. Also,
ammonia could form salts such as ammonium sulfate
which has had a serious physiological effect (76).
The presence of such compounds as HF and HC1
in the flue gas could present both corrosive and toxic
2S9-620 O—68 3
hazards. Although such compounds have not been
reported directly as components in the flue gas, the
problems relative to corrosion in incinerator boiler
units may be due to these compounds. It has been
shown that industrial gaseous effluents containing
minute quantities of HF and HC1 cause corrosion and
represent a highly toxic health hazard.
EFFECTS OF FURNACE OPERATION ON POLLUTANTS
It should be recognized that the primary purpose
of an incinerator plant is the reduction in volume and
combustible content of the refuse to obtain maximum
use of landfill space without polluting the atmosphere,
ground, or water supplies with the incinerator gases
or residue.
These conditions cannot be met without adequate
incineration of the combustible content of the refuse.
This requires a stable operating condition in the
furnace to retain the combustible material and prod-
ucts of combustion in a furnace atmosphere that
provides the necessary temperature and oxygen to
ensure acceptable burnout.
There are a number of features of incinerator com-
bustion which directly affect the composition of the
effluent stream from burning refuse. The variables
which have been considered are: Percent underfire
air; percent overfire air; heat of incineration (furnace
temperature); fuel bed agitation; incomplete com-
bustion; oxidation; and percent excess air. The effects
of these seven parameters on the effluent stream
cannot always be considered individually but must
be considered in conjunction with each other.
For purposes of this study, the effect of these
variables has been considered for a conventional
refractory wall furnace with spray cooling of the
flue gas. Figure 1 illustrates design and operating
conditions for such an incinerator when burning a
typical refuse.
It is anticipated that the operations of this incin-
erator would be maintained with a total of 150
percent excess air flow through the grates and addi-
tional overfire air to bring the furnace exit gas to a
condition of approximately 200 percent excess air,
or 6 percent CO2.
Maximum furnace temperature in the zone of active
burning is calculated to be approximately 2,250° F.
The gases would be cooled to approximately 1,260° F
when they leave the furnace to enter the spray cham-
ber by dilution with excess air and heat loss to the
furnace walls. The exit gases from the furnace would
-------
^J
. \
J 2250°F
^ -—
J
-...,.:-.. ' . J
760°F ^.^
^ "
/ I680°F //
.' I20%EXCESS AIR
,' / / /
'' ^' /
126
20
^-
^/ 37%EXCESSAIR^----" 103% EXCESS A IR_ ^^ " / ' /
^-" ""' ,-- """ """ ^" /*
^ """" -^ "^ X
~-^^ 1 3O90°F
M~"T>>^/ 0% EXCESS AIR
] TT~*>^^
i ' T^-r-^^.^
r^r~T^*i
ZONE 1 - 1 7. 8 V. » '1
ULTIMATE ANALYSIS OF
REFUSE AS FIRED
CARBON 27.6%
HYDROGEN 3.8
/
/
1
/
1
\
\
\
\
i
2040°F
124% EXCESS AIR
' 1 1 1 1 1 II 1
ZONE 2 - 22.8%"
^
\
\
\
\
\
\
\
2140 °F
109% EXCESS AIR
1 1 1 1 1 1 1 1
ZONE 3 - 14.0% »
\
1 7.5% OF TOTAL AIR INTRODUCED
82.5% OF TOTAL AIR INTRODUCED
/
\
\
\
\
x
\.
\
\
1
4IO°F
1518% EXCESS AIR
II ; ! 1 1 1 1 1 1 1 1 1 II 1
ZONE 4 - 27. 7 '/, *
AS OVERFIRE AIR.
THROUGH GRATE
i i i
OXYGEN 245
NITROGEN 0.3
SULPHUR O.I
« THESE FIGURES INDICATE PERCENT
TOTAL AIR FLOW THROUGH GRATE
OF
ZONES
MOISTURE 20.0
ASH 23.7
20O% EXCESS AIR
NOTE: CALCULATIONS
ASSUME COMBUSTION
TO BE COMPLETE. DELAYED
COMBUSTION LOWERS
FURNACE TEMPERATURES
AND RAISES EXIT
TEMPERATURE.
>
K
g
W
1000%
HEATING VALVE 5069BT.u./LB
FIG. 1. Calculated furnace conditions in a reforactory furnace at 200 percent excess air.
-------
special studies for incinerators
11
be cooled with water sprays to a temperature of
550 F prior to entering the air pollution control
equipment.
As mentioned above, the heat of incineration (fur-
nace temperature) plays a primary role in the genera-
tion of chemical pollutants due to thermal decompo-
sition of refuse components. No significant correlation
was found between furnace temperature and particu-
late emission. Higher furnace temperatures coupled
with excess air availability tend to reduce the amount
of organic pollutants since continuing oxidation
reactions of such materials result in combustion
products of carbon dioxide (CO2) and water vapor.
The available data relating grate action to pollutant
generation were very limited. It was generally indi-
cated by extrapolation to equivalent undergrate air-
flows that the particulate emission increased with
more violent grate action.
Available data on underfire airflow through the
grates and fuel bed indicated a significant effect on the
generation of particulates. Particulate weights in-
creased quite rapidly with an increase in underfire
airflow (P).
The distribution of particle size appeared to vary
with combustion efficiency, underfire airflow, and
character of refuse. Furnaces operated in excess of
rated capacity showed a larger weight of particulate
matter per pound of flue gas. Size analysis of this
particulate indicated low percentages of particulates
smaller than 10 microns in size. On the other hand,
furnaces operated with low underfire air rates and at
less than rated capacity showed large percentages of
particulates smaller than 10 microns in size.
Increasing amounts of underfire air also tended to
decrease the amount of oxides of nitrogen and alde-
hydes in the flue gas as illustrated in tables 34 and 35
in appendix A.
No correlation was found between overfire airflow
and particulate emission. Air jetted into the fuel bed
may raise particulate emission.
Higher percentages of excess air decrease the amount
of carbon monoxide in the flue gas and aid the oxi-
dation reactions, thereby decreasing the amounts of
organic pollutants as mentioned above.
EVALUATION OF AIR POLLUTION CONTROL
EQUIPMENT
There are three major parameters to be considered
when specifying control equipment. These are as
follows: Particulate loading (amount and size); volume
of gas to be handled; solubility of certain constituents
of the incinerator flue gas in water.
Particulate Loading
The quality of particulate matter in the furnace
exit gas and the size of this particulate matter are the
determining factors in selecting the efficiency re-
quirements of the air pollution control equipment.
The review of published and unpublished test
reports shows a wide range of particle size distribution
between operating plants. The approximate limits of
this distribution are shown by the shaded area of
figure 2. The solid line in this figure represents analysis
of the available data as to a representative distribution
tha-t should be obtained from normal operation of a
modern continuous feed incinerator furnace. This
indicates approximately 30 percent by weight of the
particulate matter will be less than 10 microns in size
while 75 percent by weight would be less than 250
microns in size.
The quantity of particulate matter is primarily a
function of the underfire airflow through the grates
(9). Analysis of this reference and data from other
unpublished test reports indicates that approximately
3 pounds of particulate matter per thousand pounds
of dry flue gas (1.61 grains per standard cubic foot)
can be expected during normal operation. This is
based upon an estimated average airflow through the
grates equivalent to 150 percent excess air. Additional
overfire air will increase the total excess air to approxi-
mately 200 percent in the flue gas entering the air
pollution control equipment.
In order to obtain a dust loading which will meet
the Federal Air Pollution Code Requirements of less
than 0.2 grain of particulate matter per standard
cubic foot of dry gas at 12 percent CO2, particulate
control equipment having an overall efficiency of
not less than 94 percent will be required. This is
based upon operation with an approximate CO2
content in the flue gas of 6 percent at the 200 percent
excess air conditions. The particulates at 6 percent
CO2 must be less than 0.1 grains per s.c.f. to meet the
code requirements when corrected to a 12 percent
CO2 condition.
The dust loading specified above is considered to
be representative for the various plant designs con-
sidered. This loading has been selected to provide
for high underfire airflows in active burning areas
with moderate agitation of the fuel bed providing
a large mass flow of particulate matter. The percentage
-------
12
DAY & ZIMMERMANN
10
10 20 30 40 50 60 70 6C
PERCENT LESS THAN STATED SIZE
FIG. 2. Particle size distribution in incinerator flue gas.
90
95
98 99
of material smaller than 10 microns in size is based
upon a reasonably good quality of burnout of the
particulate matter in the combustion chamber.
Volume of Gas to be Handled
The use of heat recovery equipment, excess air
for gas cooling or spray water for gas cooling will
alter the volume of gas entering the control equip-
ment and therefore affect the size of the equipment.
The addition of heat recovery equipment will
reduce the gas volume from combustion of a given
weight of refuse in two ways. First, the removal of
heat from the furnace exit gases will effect a reduction
in the specific volume of gas leaving the furnace.
Second, equipment manufacturers recommend opera-
tion of water cooled furnaces at lower excess air levels
thereby reducing total gas weight and volume.
The use of dilution air for cooling the furnace exit
gases results in a maximum volume of gases entering
the dust control equipment. The addition of water
to the gas stream reduces gas volume and temperature
by its evaporative cooling effect without adding the
additional volume that dilution cooling air requires.
-------
special studies -for incinerators
13
The net effect of the three methods of gas cooling
on total gas volume is shown on the graph in figure 3.
The effect of these methods of cooling the products
of combustion of a 250-ton-per-day incinerator furn-
ace operated at 150 percent excess air through the
grates is indicated also in figure 3. The operating cost
and the capital investment required for dust collection
equipment are a function of both gas volume and
300,000-
250,000 —
LJ
D
Q
g 200,000-
Q_
l/l
150,000-
100,000-
50,000-
-250,00 3
ADDITIONAL VOLUME
COOLING
WITH AIR DILUTION
I
ADDITIONAL VOLUME
COOLING WITH
SPRAY WATER
VOLUME GAS PRODUCTS
-------
DAY Sc ZIMMERMANN
weight. As a result, the final weight and volume
determined by the method of gas cooling has an effect
on annual operating expense.
Solubility of Gases in Water
Table 35 in appendix A lists the gaseous pollutants
in the incinerator flue gas with their water solubility.
Since a water scrubbing step is included in several
of the air pollution control systems studied, the solu-
bility in water of such pollutants must be considered.
Types of Control Equipment
For the purpose of this study, several types of air
pollution control equipment were investigated to
evaluate their anticipated collection efficiency, relative
costs, space requirements, and operating limitations.
The types of equipment considered were as follows:
Settling chamber; mechanical cyclone; wet scrubber;
electrostatic precipitator; and, baghouse filter.
The relative features of the above are described in
the text following with a summary of pertinent data
in table 7.
Settling Chamber.—In the operation of a settling
chamber, the velocity of the flue gases are reduced
thereby permitting the larger particles to settle out.
The following settling rates indicate the gas velocities
in a settling chamber must be extremely low if par-
ticles smaller than 30 microns are to be separated.
30-micron particle—settling vel.= lO'/rnin
10-micron particle—settling vel.= I'/min
1-micron particle—settling vel. = l/4'/rJ}in
To improve separation, baffles may be inserted
upon which the particles will impinge. Ash retention
is improved by wetting the baffles and ash removal
is accomplished by flushing the ash into a wet sump.
The advantages of this type of equipment are as
follows: Simplest method of fly ash control; low
maintenance cost; and, capability of being operated
with natural-draft chimney.
The disadvantages are as follows: Large size;
high installation cost; low collection efficiencies of
40 to 60 percent; and, unsuitability for collection
of smaller size particles.
Due to their low efficiency, settling chamber? will
not meet the air pollution code requirements unlc^
used in conjunction with equipment of higher
efficiency.
Mechanical Cyclones.—In the operation of mechanical
cyclones the particles are thrown to the periphery of
the cyclones by centrifugal force and are allowed to
settle out.
The advantages of mechanical cyclones are the low
initial cost and the low operating cost.
The disadvantages are: Low efficiency, since only
larger size particles are efficiently removed; erosion
of the lower tube by abrasive fly ash; and, moisture
control problems.
To overcome one of the disadvantages, abrasion
resistant linings may be used. Flushing of the fly ash
with water has been tried in the hydrowall cyclone,
a modification of the conventional cyclone which is
still in the development stage.
Advantages of the hydrowall type of cyclone have
been reported as follows: Reentrainment of fly ash
prevented; efficiency improved; erosion reduced.
Some difficulty has been experienced with plugging
of the cone sections of hydrowall installations.
Mechanical cyclones will not completely meet the
air pollution code requirements. They can be of great
value if used in conjunction with other equipment
sich as an electrostatic precipitator which could col-
lect the smaller size particles.
Wet Scrubbers.—There are two general classifications
of wet scrubbers, the low energy type and the high
energy type. In the low energy scrubbers, water is
sprayed over the gas stream causing particulates to
impinge on the water droplets and thereby be re-
moved from the gas phase.
The advantages of a low energy scrubber are as
follows: Low maintenance; low cost—both initial and
operating.
The disadvantages are as follows: Low efficiency.
If the water droplets are larger than 200 times the
diameter of the particles, the particles will not be
effectively removed from the effluent stream; efficiency
for removal of water soluble gases is low because of
the limited amount of contact of the gas stream with
the scrubbing liquid.
In a high .energy scrubber the water sprays are fine
and distributed more evenly, and the gas stream path
is more tortuous because of the insertion of baffles,
use of packing, or similar devices.
The advantages of a high energy scrubber are as
follows: (1) Efficiency of ninty-five percent or greater.
This is obtained by increasing the interface between
the effluent gas stream and the scrubbing water.
Baffles or packing increase the impingement area for
removal of the particulates; (2) removal of water sol-
uble gases. This is accomplished by increasing the
amount of scrubbing liquid in contact with the gas
stream. A flushing stream below the baffles or a
flooded bed above the packing increases the time for
-------
special studies for incinerators
15
removing water soluble gases; and, the (3) moderate
cost of installation and operation.
The disadvantages are: (1) High maintenance cost
when baffles or packing become plugged; (2) antic-
ipated corrosion because of the change in pH of the
scrubbing water after removing gases and certain
particulates; (3) need for equipment to remove partic-
ulate matter from washwater and need to neutralize
water before return to source; (4) difficulty with
water recirculation because of particulates; (5) re-
quirement for large flow of water; (6) a water-sat-
urated gas is emitted from the stack, resulting in a
large vapor plume which can be objectionable.
Where the vapor plume is not objectionable, the
use of high energy scrubbers can meet the require-
ments of pollution control equipment for municipal
incinerators.
Two methods can be considered for elimination of
the vapor plume where such a plume is objectionable.
The first method consists of reheating the stack gases
to increase the temperature and thereby permitting
greater dispersion of the gases in the atmosphere be-
fore condensation takes place, making the presence
of moisture in the stack effluent less noticeable. The
second method consists of subcooling the gases to ap-
proximately 100° F. which will reduce the total mois-
ture content of the gas stream to about 0.10 of that
present in the saturated gases at 170° F. This will
reduce the total moisture content of the plume.
Water conditioning equipment must be provided to
process the large quantities of water required for a
high energy wet scrubber. One equipment manufac-
turer requires approximately 750 gallons of water per
minute for a scrubber and quench unit designed to
handle the products of combustion from a single in-
cinerator furnace of the size considered in this; report.
Assuming that this water is pumped from the nearby
river, a river water intake of 3,000 g.p.m. capacity,
suitable'filtration equipment to remove solids which
might plug spray nozzles and water treatment equip-
ment to remove the fly ash from the scrubber dis-
charge water and to neutralize the acid content of the
water would be required.
It is estimated that a minimum retention time of 60
minutes would be required to obtain satisfactory
clarification of the waste water stream. This would
require four clarifier units, approximately 35 feet in
diameter. The fine particle content of the settled
slurry will make dewatering difficult, necessitating
some form of slurry handling system to discharge the
settled flyash to ash removal trucks. Lime and alum
feed equipment should be provided to improve co-
agulation and neutralize the overflow before return to
the river. Temperature rise of the scrubber water will
be appreciable. An 18.5° F. rise is anticipated.
Total water requirements to include additional
cooling of the gas to reduce the plume are estimated at
6,000 g.p.m. The temperature rise of this water would
be 100° F. This would double the size of the intake
structure, pumping equipment, clarifier equipment,
pipelines, etc. This approach is not justified if the
plume can be accepted. Likewise, gas-to-gas heat
exchangers to raise the temperature of the gases are
quite expensive to maintain and operate and their
use is not recommended.
The Anacostia River in the District of Columbia is
a tidal river with summer water temperatures ap-
proaching 100° F. Temperatures of this magnitude
are unfavorable to aquatic life matter. Adding more
heat from wet scrubber effluents would aggravate the
existing temperature conditions. It is doubtful that
permission could be obtained to return water to the
river with a temperature rise in excess of 5° F. if the
thermal pollution of this river is to be controlled. This
5° F. temperature rise requirement can be met only by
circulation of greater quantities of water or by the
addition of cooling tower facilities for heat dissipation
to the atmosphere.
The adjacent electric power generating station is
now in the process of installing cooling tower equip-
ment for their latest plant expansion in order to con-
trol the water temperature to their turbine condensers.
Electrostatic Precipitators.—In the operation of elec-
trostatic precipitators, the particles are first electri-
cally charged and then attracted to plates which have
an opposite charge. The particles lose their charge
upon contact with the plates and migrate down to
collection hoppers. The efficiency is dependent on the
resultant vector between the inertia of the particles
and electrostatic attraction to the plates.
The advantages of electrostatic precipitators are as
follows: (1) Low operating cost; (2) high efficiency
(90 to 99 percent); (3) highest efficiency for particles
less than 10 microns in size; (4) ability to handle both
dusts and mists.
The disadvantages are as follows: (1) High purchase
and installation costs; (2) necessity of uniform gas
distribution across inlet of collector to obtain design
efficiency; (3) critical electrode voltage (too little
reduces efficiency and too much causes electric arcing);
(4) two limiting factors related to velocity and there-
fore capacity: Particles must have time to build up
-------
16
DAY & ZIMMERMANN
charge, and, gas velocity must be low enough so as
not to reentrain particles; (5) the tendency of carbon
to lose its charge before it is collected and high
resistant inorganics are hard to charge. This can be
corrected by two ways: The insertion of a cyclone
before the precipitator which will remove particles
greater than 10 microns in size, and, the addition of
moisture to reduce the resistance of the inorganics;
(6) critical temperature (optimum temperature range
is 500° to 600° F. because of resistance of particles to
being charged at higher or lower temperatures).
Electrostatic precipitators should meet the require-
ments of pollution control equipment for municipal
incinerators. However, the application of an electro-
static precipitator to a U.S. municipal incinerator
would be unique; therefore, serious consideration
must be given to potential operating problems. These
problems could consist principally of erosion, corro-
sion and fouling, and passing of large particulate
matter.
It is probable that the problems of erosion, fouling
by fatty acid particulates, and passing of large partic-
ulates can be reduced to acceptable levels if the
electrostatic precipitator is preceded by a large-
diameter mechanical cyclone collector constructed
with an abrasion-resistant lining. This will result in
a total draft loss equivalent to the wet scrubber
installation. The problem of corrosion can be reduced
by good temperature control equipment and adequate
insulation of the equipment to reduce internal dew
point condensation. There will remain a possibility of
some fouling due to accumulations of cementatious
fly ash. This must be considered a normal operating
problem and will require internal cleaning at scheduled
intervals along with other routine maintenance such
as replacement of electrode wires.
The use of alkali cleaners would be effective in
removing any fatty acid films. Alkaline solutions
can be used satisfactorily on carbon steel and stainless
alloy steels. Wash solutions are normally used be-
tween 140° to 200° F., and can be used as a spray.
Wash should be followed with a rinse water spray.
Bagbouse Filters.—In the operation of baghouse
filters, the gases pass through the bag filter and the
large particles are filtered out. After a few seconds
the large particle buildup on the bag enables the
smaller particles to be filtered out.
The following listing of advantages and disadvan-
tages of using a baghouse filter is based on experience
with an installation of a pilot baghouse on the
municipal incinerator of the city of Pasadena, Cali-
fornia.
The advantages are as follows: (1) High efficiency—
99 percent; (2) moderate press drop, 3" to 5" water;
(3) the filtering out of both small and large particu-
lates; (4) the ability to filter out SO3 due to nature
of ash-cake on bagfilter.
The disadvantages are as follows: (1) High initial
cost; (2) costly bag replacement; (3) requirement of
greater control of combustion, to eliminate sticky-
soot formation which clogs filters; (4) necessity to
control cooling to prevent formation of moisture on
filter which will shorten bag life.
Additional comments and recommendations were
received from the personnel concerned with the
installation at Pasadena. These may be summarized
as follows: (1) The flow through the baghouse is
opposite to that of conventional units. The gas enters
the bag on the outside and exits through the partially
collapsed bag upward through the plenum. This
scheme permits the spider framework to be on the
clean side of the bag and eliminates past failures due
to abrasion from buildup on the spider. It also has the
advantage of eliminating bag damage due to collaps-
ing the bag over hard cakes that are periodically
formed in the bag. Since the bag is normally in a
semirelaxed position, the cakes that are formed can
be literally "popped off" with no damage to the bag
when it is inflated (cleaning cycle); (2) the flue gas
should not exceed 500° F. so as to extend bag life. If
this is accomplished bag life should be about 1 year;
(3) cannot let unit cycle below dew point because of
bag life; (4) pulsating damper speed in the cleaning
fan discharge is very critical (a minimum of 250
r.p.m. to a maximum of 500 r.p.m. has some merit);
(5) internal framework should be fabricated from 316
stainless steel. Carbon steel oxidizes and results in
bag failure. Aluminum does not withstand prolonged
elevated temperatures.
The use of a baghouse filter for air pollution control
equipment for municipal incinerators should not be
considered at this time due to lack of sufficient
satisfactory experience.
ESTIMATES OF CAPITAL AND OPERATING- COSTS FOR
AIR POLLUTION CONTROL EQUIPMENT
Two concepts for removal of air pollutants from
the incinerator flue gas stream were made the subject
of capital investment and operating cost estimates.
-------
special studies for incinerators
17
In both cases gas flow is created by an induced draft
fan which discharges to a 100-foot chimney.
TABLE 7
TYPES OF CONTROL EQUIPMENT
Equipment type
Electrostatic
precipitator.
Scrubber (flooded
plate).
Mechanical cyclone
(60" tangential).
Baghouse filter .
Settling chamber ....
Compara-
tive space
C%)
100
33
33
110
67
Efficiency
(%)
90-99
90-99
75-90
99
40-60
Basic limitations
Does not remove
soluble gases.
No installation
working in U.S.
municipal inciner-
ators.
Efficiency low on
large particles.
Possible mist emit-
ting from stack.
Clarification and
neutralization of
wash water re-
quired.
High water usage.
Low efficiency on
small particles.
Erosion from abra-
sive fly ash.
Multitude of vari-
ables to be con-
trolled coupled
with the com-
plexity of the
effluent stream.
Low efficiency.
One arrangement provides for passing the 1,260° F.
flue gas from the furnace through a refractory spray-
cooling chamber where the temperature is reduced
to 500° F. The moisture-laden gas then is passed
through a multicyclone separator. The gas then enters,
at a low velocity of 5 feet per second, and passes
through an electrostatic precipitator unit.
The alternate concept consists of passing the hot
furnace gas directly through a wet scrubber such as
the flooded-plate type with a prequench' unit. Water
supply for this unit would be supplied from a pumping
station on the Anacostia River. Water discharge from
the scrubber would be delivered to a liquid clarifier.
Overflow would be conducted back to the river by
pipeline. Slurry removed would be pumped to residue
trucks for land fill disposal.
Either of these systems are capable of removing
94 percent or more of the particulate matter over
size greater than 10 microns, and close to 100 percent
of particulates less than 10 microns in size.
In conclusion, we have charted annual operating
costs (table 8) and estimates of some of the items
adding to capital costs (table 9) for these installations.
These costs are presented in some detail so that the
effects of relative equipment sizes and accessory equip-
ment can be evaluated.
It should be noted that the building costs, spray
cooling chamber, steel ductwork, insulation, elec-
trical work, and instrumentation add appreciable
to the cost of installation of the electrostatic precipi-
tator and mechanical cyclone. These higher costs are
partially offset by the costs of the river water pumping
station, water clarification system, refractory flues
and piping for the scrubber installation.
TABLE 8
ESTIMATED ANNUAL OPERATING COSTS POR TWO TYPES AIR POLLUTION
Operating costs
Maintenance
Electric power
Purchased city water.
Subtotal, operating costs
Fixed charges on capital investment 20
years at 4^ percent
Total, annual owning and oper-
ating cost
Air pollution control
equipment
Electrostatic
and mechan-
ical
$139, 000
160,600
27,900
327, 500
185,000
512,500
Wet scrubber
$127, 700
130, 800
1,000
259, 500
141, 500
401,000
1 Only those variables are included which are influenced by the
type of equipment considered.
REFERENCES
(0 KAISER, E. R. Chemical analyses of refuse
components. Paper 65-WA/PID-9. In Pro-
ceedings, American Society Mechanical Engi-
neers, Nov. 7-11, 1965. 5 p. (Also private
communications, E. R. Kaiser.)
(2) REHM, F. R. Unpublished test data.
(3) JACOBS, M. B., M. M. BRAVERMAN, S. HOCH-
HEISER, and I. ETTINGER. Sampling and
analysis of incinerator flue gases. Paper 2464.
,289-920 O—6
-------
18
DAY & ZIMMERMANN
In Proceedings, Air Pollution Control Asso-
ciation, 51st Annual Meeting, Philadelphia,
May 25-29, 1958.
(4) WESTERN OIL AND GAS ASSOCIATION. The smog
problem in Los Angeles County. Los Angeles,
Western Oil and Gas Association, 1954.
TABLE 9
COMPARATIVE CAPITAL COST ESTIMATES, SELECTED ITEMS FOR AIR POLLU-
TION CONTROL STUDY, FOUR-UNIT INCINERATOR PLANT
General building contract:
Incinerator building and founda-
tions
Mechanical contract:
Refractory furnaces and flues
Spray cooling chamber
Insulation
Instrumentation
Installation of purchased equip-
ment. . . .
Piping ....
Purchased equipment:
Fans and drives
Pumps and drives
Air pollution control equipment. . .
Clarifier equipment
Electrical contract: Power and lighting
Subtotal physical cost
Engineering and field supervision
Contingency
Escalation to December 1968
Total incremental physical cost .
Type of air pollution
control equipment
Electro-
static
and
mechanical
$606, 700
606,700
204,000
221, 900
324,000
133, 700
60,000
132,000
1, 075, 600
135, 900
396,000
531, 900
195, 000
2, 409, 200
169,000
241,000
120, 500
2, 939, 700
Wet
scrubber
$447,000
7,200
45,000
499, 200
248, 400
228,000
26,500
42,000
60,000
58,500
663, 400
125, 900
19,000
337, 300
64,800
547,000
129,000
1, 838, 600
130,000
185, 900
92,900
2, 247, 400
0) MARKLEY, K. S. Fatty acids. 2v. New York,
Interscience Publishers, Inc., 1960.
(<0 HUNTER-WAGNER ENGINEERING DIVISION. How
we get our plastics/plastics world flow chart
of major plastic materials. Kansas City,
Black, Sivalls, and Bryson. 1 p.
(7) SPENCER, F. J. Progress in polymers today.
Hydrocarbon Processing, 45(7): 83-102, July 1966.
(5) SISLER, H. H., C. A. VANDER WERF, and A. W.
DAVIDSON. College chemistry, a systematic ap-
proach. New York, The Macmillan Company,
1953. 623 pp.
(9) STENBURG, R. L., R. P. HANGEBRAUCK, D. J.
VON LEHMDEN, and A. H. ROSE, JR. Field
evaluation of combustion air effects on at-
mospheric emissions from municipal incin-
erators. Journal of the Air Pollution Control
Association, 12(2): 83-89, Feb. 1962.
(70) KAISER, E. R. Refuse composition and flue-gas
analyses from municipal incinerators. In Pro-
ceedings, 1964 National Incinerator Confer-
ence, American Society Mechanical Engineers,
New York, May 18-20, 1964. p. 35-52.
(if) SHAW, J. T., and P. D. GREEN. Oxidation of
sulfur dioxide in air at 950° C: Cooperative
influence of carbon monoxide and nitric oxide.
Nature (London), 211(5054): 1171-1172, Sept.
1966.
(72) HAMA, G. M., and L. C. CURLEY. Corrosion of
combustion equipment by chlorinated hydro-
carbon vapors. Air Engineering, 7(4): 38-42,
Apr. 1965.
(73) HANGEBRAUCK, R. P., D. J. VON LEHMDEN, and
J. E. MEEKER. Emissions of polynuclear hydro-
carbons and other pollutants from heat-
generation and incineration processes. Journal
of the Air Pollution Control Association, 14(7):
267-278, July 1964.
(if) DERNEHL, C. U. Health hazards associated with
polyurethane foams. Journal of Occupational
Medicine, 8(2): 59-62, Feb. 1966.
(75) DODSON, V N. Ann Arbor case reports. I.
Asthma and toluene di-isocyanate exposure.
Journal of Occupational Medicine, 8(2): 81-83,
Feb. 1966.
(7(5) JACOBS, M. B. Health aspects of air pollution
from incinerators. In Proceedings, 1964 Na-
tional Incinerator Conference, American So-
ciety Mechanical Engineers, New York, May
18-20, 1964. p. 128-131.
-------
special studies for incinerators
19
(.Z7) ENCYCLOPEDIA BRITANNICA. Refuse analysis dirt
and vacuum catch, v. 19. Chicago, Encyclo-
pedia Britannica, Inc., 1944. p. 60.
FURNAS, C. C. Rogers' industrial chemistry. 2 v.
New York, D. Van Nostrand Co., Inc., 1942.
KENT, J. A. Riegel's industrial chemistry. New
York, Reinhold Publishing Corp., 1962. 963 p.
(20) WEST, E. S., and W. R. TODD. Textbook of bio-
chemistry. New York, The Macmillan Com-
pany, 1951. 1,345 p.
(2J) HERBERT, D. B. The nature of incinerator slags.
In Proceedings, 1966 National Incinerator Con-
ference, American Society Mechanical Engi-
neers, New York, May 1-4, 1966. p. 191-194.
(22) REGIS, A. J". X-ray spectrographic analysis of
incinerator slags. In Proceedings, 1966 Na-
tional Incinerator Conference, American So-
ciety Mechanical Engineers, New York, May
1-4, 1966. p. 195-198.
(23) JENS, W., and F. R. REHM. Municipal incinera-
tion and air pollution control. In Proceedings,
1966 National Incinerator Conference, Ameri-
can Society Mechanical Engineers, New York,
May 1-4, 1966. p. 74-83.
(24) SAX, N. I. Dangerous properties of industrial
materials. New York, Reinhold Publishing
Corp., 1957. 1,467 p.
BIBLIOGRAPHY
CLARKE, L. Manual for processing engineering calcula-
tions. New York, McGraw-Hill Book Co., Inc.,
1947. 438 p.
MANUFACTURING CHEMISTS' ASSOCIATION, INC. Air
pollution abatement manual; gas and vapor abatement.
Manual sheet P-ll. Washington, Manufacturing
Chemists' Association, Inc., 1953. 29 p.
LENEHAN, J. W. Air pollution control in municipal
incineration. Journal of the Air Pollution Control Asso-
ciation, 12(9): 414-417, Sept. 1962.
HUGHSON, R. V Controlling air pollution. Chemical
Engineering, 73(18): 71-90, Aug. 1966.
PHELPS, A. H. What doesn't go up must come down.
Chemical Engineering Progress, 62(10): 37-40, Oct.
1966.
HEMEON, W. C. L. Gas cleaning efficiency require-
ments for different pollutants. Journal of the Air
Pollution Control Association, 12(3): 105-108, Mar.
1962.
O'CONNOR, C.,
-------
appendix a
TABLE 10
REFUSE ANALYSIS I DIRT AND VACUUM CLEANER CATCH '
Dirt, soil =1.68%
v i u a84%
Vacuum cleaner catch=- ,n07—~,—7—
2.52% of refuse
Probable chemical constituents:
Oxygen (02)
Silicon (Si)
Aluminum (Al)
Iron (Fe)
Calcium (Ca)
Magnesium (Mg)
Potassium (K)
Sodium (Na)
80 miscellaneous elements. .
Percent
47.0
27.0
8.0
5.0
2.8
2.8
2.8
2.8
1.7
1 Abstracted from literature, cited in reference 17.
TABLE 11
REFUSE ANALYSIS: GLASS AND CERAMICS 1
Glass and ceramics=8.50% of refuse
Composition of typical glass:
Silicon dioxide (SiO2)
Boron oxide (B2Oa)
Aluminum oxide (A1O3).
Sodium oxide (Na2O)....
Calcium oxide (CaO)
Potassium oxide (K£>)...
Lead oxide (PbO)
Sulfur trioxide (SOs)
Arsenic oxide (AszOs)
Composition of ceramics:
Silicon dioxide (SiO2).
Boron oxide (Buds).
Aluminum oxide (Al2Os).
Sodium oxide (Na2O).
Calcium oxide (CaO).
Potassium oxide (K2O).
Titanium dioxide (TiOj).
Chromium oxide (Cr2Os).
Beryllium oxide (BeO).
Zirconium oxide (ZrO2).
Tin oxide (Sn2O).
Magnesium oxide (MgO).
Fluorides.
Percent
67.0-96
1.0-16
1.0- 4
4.0-18
0.3-13
0.1-12
15.0
0.4-00.7
0.5- 1
1 Abstracted from literature, cited in reference 18.
TABLE 12
REFUSE ANALYSIS: METALS '
Metallic constituents: Metals = 7.53% of refuse
Silicon (Si).
Carbon (C).
Nickel (Mi).
Chromium (Cr).
Magnesium (Mg).
Copper (Cu).
Aluminum (Al).
Tin (Sn).
Iron (Fe).
Manganese (Mn).
Molybdenum (Mo).
Cadmium (Cd).
Zinc (Zn).
Bismuth (Bi).
Sulfur (S).
Tungsten (W).
Mercury (Hg).
Arsenic (As).
Vanadium (V).
Antimony (Sb).
Phosphorus (P).
Beryllium (Be).
1 Abstracted from literature, cited in reference IS.
TABLE 13
REFUSE ANALYSIS: WOOD, PAPER PRODUCTS, PLANT AND FOOD WASTES !
Wood and balsam spruce = 2.52%
Wood (paper) products = 56.01%
Food wastes= 9.24%
Plants and grass= 7.56%
75.33%
of refuse
Probable constituents, composition:
Cellulose
Pentosans
Monosaccarides
Oligosaccarides
Polysaccarides
Lipids—fats
Proteins (polyamides)
Ash:
SiO2 .
A1203
Carbohydrates.
Book & magazines
(24.05% ash).
Cardboard (7.79% ash).
Mixed paper (6.55%
ash).
Newsprint (3-93% ash).
1 Abstracted from literature, cited in references 10, IS, 19, and 20.
21
-------
22
DAY & ZIMMERMANN
TABLE 14
REFUSE ANALYSIS
PLASTICS '
Plastics = 3.50% of refuse
Tyfe
Acrylonitrile butadiene styrene..
Cellulose acetate
Cellulose acetate butyrate
Cellulose nitrate
Melamine formaldehyde
Polyethylene
Poly vinyl dichloride
Urea formaldehyde
Urethane
Polymethyl methacrylate
Polypropylene
Polystyrene
Polyvinyl acetate
Polyvinyl chloride
Source
Shoe heels, appliances.
Pens, handles, frames, combs,
toys.
Pens, handles, frames, combs.
Pens, pencils.
Bottlecaps, buttons.
Film, flexible bottles,
containers.
Bottles, toys.
Bottlecaps, buttons, dinner-
ware.
Coatings, laminates, adhesives.
Buttons.
Fibers, packaging, films,
appliances.
Combs, buttons, containers,
toys, housewares.
Records.
Films, bottles, toys.
TABLE 16
REFUSE ANALYSIS: PAINTS AND OILS L
Paints, oils, removers = 0.84%
of refuse
Composition:
White lead.
Titanium dioxide (TiOz).
Zinc oxide (ZnO).
Zinc sulfide.
Calcium chloride (CaCl2)
and other hygroscopic
salts.
Chromium (Cr).
Alkyd and phenol alde-
hydes.
Acetone.
Methanol.
Benzene.
Paints, oils, removers = 0.84%
of refuse
Methylene chloride.
Maleic anhydride.
Phthalic anhydride.
Polystyrene.
Phenol.
Cresols.
Cresylic acid.
Xylenols.
Acrylates.
Poly amides.
Urea.
Vinyl.
Abstracted from literature, cited in references 18 and 19.
1 Abstracted from literature, cited in references 6 and 7.
TABLE 15
REFUSE ANALYSIS: RAGS '
I
Rags = 0.84% of refuse
Cotton
Nylon
Silk
Orion and Acrilan. ...
Dynel
Dacron
Rayon
Wood
Composition
Cellulose, sulfur.
Diamine, diacarboxylic acid, caprolactam.
Complex polyamides.
Acrylonitrile.
Copolymer of acrylonitrile and vinyl
chloride.
Complex polyester.
Cellulose acetate, ethyl cellulose, viscose
rayon.
Protein—complex polyamide.
1 Abstracted from literature, cited in references 18 and 19.
TABLE 17
REFUSE ANALYSIS: LEATHER J
Leather=0.42 of refuse
Glycerides
Composition
Natural fats — esters
of glycerin.
Percent
95
5
1 Abstracted from literature, cited in references IS and 19.
-------
special studies for incinerators
23
TABLE 18
REFUSE ANALYSIS: RUBBER *
Rubber=0.42% of refuse
Composition-natural:
Proteins — amino
acids .
Fatty acids, esters ....
Quebrachital
Tnnrganir salts
Rubber hydrocarbons .
Water. .
Sulfur
Percent
2 0
1.0
1 0
0 4
35.0
60 0
0 6
Composition (types") —
synthetics:
Chloroprene polymers.
Plasticized vinyl
chloride.
nitrile.
Ethylene dichloride.
Isobuty lene + isoprene.
Isobutylene +
butadiene.
TABLE 19
REFUSE ANALYSIS: MISCELLANEOUS1
Miscellaneous items of
refuse
Developers..
Dyestuff. . ..
Insecticides.
Preservatives
Flavorings and perfumes.
Composition
Nitrophenols, nitrobenzene, hydro-
quinone.
Carbazole, phenanthraquinone, anthra-
quinone, naphthalene sulfonic acids,
salicylic acid, benzaldehyde, tolu-
ides, xylenes, halogenated benzene,
aniline salts, dimethylaniline, ani-
line.
Crude naphthalene, nitro napthalene,
halogenated benzene.
Anthranilic acid.
Benzoic acid, benzaldehyde.
1 Abstracted from literature, cited in references 18 and 19.
1 Abstracted from literature, cited in references IS and 19.
TABLE 20
DATA ON FATTY ACIDS '
Common name
Acetic acid
Palmitic acid
Stearic acid
Oleic acid
Classification
Saturated
Saturated .
Saturated
Saturated
Unsaturated (9 10~) . .
Unsaturated (9 10~)
Structure
HCOOH
CH3COOH
C15Hi3COOH ....
Ci7H35COOH
CI7H33COOH
C15H29COOH
Occurrence
Obtained by pyrolysis of many organic substances.
Occurs both free and combined in the form of esters of various
alcohols in many plants.
Found in vegetable and animal fats.
Predominant component of body fats of animals. Small amounts
of fruit flesh and seed fats.
Predominant fatty acid of natural fats. Found in every plant and
animal fat. Comprises 50% or more of the fatty acids.
Widely distributed in nature. Second to oleic in frequency of
unsaturated acids.
1 Abstracted from literature, cited in reference 5.
-------
24
DAY & ZIMMERMANN
TABLE 21
DECARBOXYLATTON Or FATTY ACIDS '
Kind of fatty acid or derivative
Temperature
Additional conditions
Products
Normal lower fatty acids
stearic
stearic
stearic
Salts of saturated acids:
magnesium stearate
calcium stearate
Monoesters: ethyl stearate
300° C. (6 hours).
300° C. (6 hours).
300° C. (6 hours).
350° to 400° C....
450° C
300° C
Ordinary pressures
Vapor state in presence of SiC>2,
TiO2, CuO, ZnO.
In presence of CdO
In presence of iron oxides, A^
MgO.
Readily distilled, yields fatty acid.
6-7% Ketones, 93-94% Fatty
acids.
13% Ketooes, 87% Fatty acids.
17-24% Ketones, 76-83% Fatty
acids.
80% Acetone soluble material:
80% fatty acids.
30% Acetone soluble material:
30% fatty acids.
Stearic acid + ethylene.
1 Abstracted from literature, cited in reference 5.
TABLE 22
AMOUNT OF POLYNUCLEAR HYDROCARBONS, INCINERATOR EFFLUENT
Benzo(a)pyrene
Pyrene
Benzo(f)pyrene . .
Coronene
Fluoranthene
Benzo(tf)anthracene
Micrograms/gm- of
parti culate
0.016
1.9
08
06
2 2
.09
1 Data on a 250 ton/day municipal incinerator (breeching before
settling chamber) when burning rubber tires, abstracted from lit-
erature, cited in reference 13.
TABLE 23
HALOGENATED HYDROCARBONS !
Generic name
Trichloroethylene
Perchloroethylene
Carbon Tetrachloride... .
Methylene Chloride
Methyl Chloroform
"Freon" F-12
"Freon" F-114
"Freon" F-ll
"Freon" F-21
Chemical formula
C2HC13;
QC1,.
CC14.
CH2C12.
CH3CC13.
CC12F2.
C2C12F4.
CC13F.
CHC12F.
1 Tabulation of the types of halogenated hydrocarbons used in
pressurized cans abstracted from literature, cited in reference 12.
TABLE 24
ANALYSIS OF INCINERATOR SLAGS '
Silicon dioxide (SiO2) '
Aluminum oxide (AlzOs)
Iron oxide (F^Os)
Titanium oxide (TiOg)
Calcium oxide (CaO)
Magnesium oxide (MgO)
Sodium oxide (Na2O) .
Potassium oxide (K2O)
Phosphorus oxide (PzOs)
Barium oxide (BaO) . .
Wet chemical analysis run on
slag (percent)
Sample B
43.01
24.85
6.00
3.31
9.28
2.47
3.28
.73
2.05
.66
1.17
Sample D
49.91
8.73
12.78
2.40
11.03
2.54
3.31
2.27
2.40
.45
2.49
Sample ,F
45.99
21.47
7.78
3.00
9.5
2.65
3.16
1.09
2.00
.62
.46
1 Data on nature of incinerator slags abstracted from literature,
cited in reference 21.
TABLE 25
ANALYSIS OF INCINERATOR SLAGS '
Slags
Silicon dioxide (SiO2)
Aluminum oxide (A^Os) ....
Phosphorus oxide (PzOs) . . ...
Potassium oxide (K2O)
Zinc oxide (ZnO)
Percent
40-52
8-25
2.0-2.5
0. 5-2. 5
9-11.5
5.5-8.5
2.2-3.5
0. 25-2. 75
1 Data on x-ray spec to graphic analysis of incinerator slags ab-
stracted from literature, cited in reference 22.
-------
special studies for incinerators
25
TABLE 26
ANALYSIS OF INCINERATOR EFFLUENTS *
[Percent]
Element
Silicon
Manganese
Chromium
Nickel
Vanadium
Iron
Tin :
Aluminum
Zinc . .
Magnesium
Silver
Lead
Stack effluent
5 +
0 1-1 0
0 1-1 0
1-10
0 1-1 0
0 001-0 01
0 5-5 0
0 05-0 5
1-10
1-10
1-10
0 5-5 0
0. 001-0. 01
0 01-0. 1
0 1-1 0
0 001-0 01
1.0+
1-10
0. 01-0. 1
Test run no. 6
Collector catch
104-
0 1-1 0
0 01-0 1
0 001-0 01
0 01-0 1
0 01-1 0
o 5-5 o
0 05-0 5
1-10
1-10
1-10
0 5-5 0
0 001-0 01
0.01-0 1
0.1-1 0
0 001-0 01
10+
0. 5-5.
0.1-1.0
Residue
10+
0110
0 01-0 1
0 001-0 01
0 01-0 1
0 01-0 1
1-10
0 1-1 0
1-10
0 1-1 0
1-10
0 5-5 0
0 001-0 001
0 01-0. 1
0 1-1 0
-0 001
10 +
0.1-1.0
0.1-1.0
Test run no. 8
Stack effluent
5-f
0 1-1 0
0 1-1 0
10 +
0 1-1 0
0 001-0 01
0 1-1 0
0 001-0 01
0 1-1 0
1-10
1-10
0 5-5 0
-0.0001
0. 01-0. 1
0.1-1.0
-0.0001
10+
1-10
0. 05-0. 5
1 Data on spectographic analysis elements reported in percent ashed material abstracted from
literature, cited in reference 23.
TABLE 27
ANALYSIS OF FLY ASH1
[Percent]
TABLE 28
SOURCES OF AMMONIA IN EFFLUENT GASES '
Silicon as SiO2 . .
Calcium as CaO
Magnesium as MgO
Sodium as NajO
Collected
in system
49.5
22.9
6.3
8.8
2.2
1
[ 6.0
1 3
3 0
Emitted
from stack
36.3
25.7
7.1
8.8
2.8
10.4
q
8 0
1 Data on fly ash analyses (weight percent) abstracted from lit-
erature, cited in reference 10.
289-620 O—68 5
Plastics :
Acrylonitrile butadiene
styrene.
Urethane (polyurethanes) .
Wood, wood products, food
wastes, plants, grass:
Chemical
Hexamethylene
diamine.
Urea
Toluene diisocy-
anate.
Hexamethylene
diamine.
Symbol
NH3
NH3 + CO2
NH3
NH3
NH3
NH3
1 Abstracted from literature, cited in references 6, 7, and 20.
-------
26
DAY & ZIMMERMANN
TABLE 29
TOXIC AND CORROSIVE CHARACTERISTICS OF ORGANIC SUBSTANCES
Name
Organic acids:
fnrmir
acetic
palmirir
stearic
oleic
palmitoleic
Aldehydes :
formaldehyde
acetaldehyde . .
Esters:
methyl acetate
ethyl acetate
ethyl stearate
CO2
CO
Phosgene, toluene diioso-
cyanate.
Halogenated hydrocarbons .
Polynuclear hydrocarbons . .
Form
Gas
Gas & par-
ticulate.
do
do
do ...
......do
Gas
do
do
do . .
do
. .do... .
do
do
do
do
Toxicity '
2
1
1
3
2
2
1
3
3
C)
C)
Corrosive
property 2
Weakly
acidic.
TABLE 31
TOXIC AND CORROSIVE PROPERTIES, POLYNUCLEAR
HYDROCARBONS '
1 Toxicity is designated as follows (2f): 0, none; 1, slight; 2,
moderate; 3, high; u, unknown.
2 Corrosive properties are reported as acidic or basic (#).
3 See table 30.
1 See table 31.
TABLE 30
TOXIC AND CORROSIVE CHARACTERISTICS, HALOGENATED HYDROCARBONS
IN PRESSURIZED CANS *
Name2
Trichlorethylene
Perchlorethylene
Carbon tetrachloride .
Methylene chloride. .
Methyl chloroform .
Freon® 12 ...
Freon® 114 .. ......
Freon® 11
Freon® 12 ..
Threshold
limit values
(p.p.m.)
100
100
10
500
350
1,000
1,000
1,000
1 000
Odor Threshold
(p.p.m.)
50
50
25
25 to 50
Below thresh-
old limit
value.
Almost odorless
.. ..do
do
-------
special studies for incinerators
27
TABLE 34
EFFECT OF AIR FLOW ON NO2 CONCENTRATION IN FLUE GAS *
Undcrfire air
(%)
20
50
80
100
Excess air
(%)
190
180
190
150
Gas temp.
(secondary
chamber)
"Fahrenheit
1 750
1 790
1 930
1 960
NO2, Ibs 1,000
Ibs dry flue
gas (converted
to 50%
excess air)
0 33
27
22
20
1 Data on summary of average emission from 250-ton per day
incinerator abstracted from literature, cited in reference 9.
TABLE 35
EFFECTS OF AIR FLOW ON ALDEHYDE FORMATION '
Underfire
air (%)
20. .. .
50
80
100
Excess air
(.%)-
190
180
190
150
Temporary
secondary
chamber
(° Fahrenheit)
1 7V1
1 790
1 QV)
1 960
Formaldehyde
(ponnds/1,000
Ibs of dry flue
gas converted
to 50 percent
excess air)
(before H2O
spray scrubber)
•2 Q Y lfV-4
2 8 X 10~*
1 7 x 10~*
1 7 x 10~~ 4
1 Data on a 250-ton-per-day incinerator abstracted from literature,
cited in reference?.
TABLE 36
SOLUBILITY OF GASEOUS POLLUTANTS IN WATER
Solubility in' water '
Carbon monoxide C^O)
Catbon dioxide (QOz)
Ammonia (NHs)
Sulfur dioxide (SOz)
Sulfur trioxide (SO3)
Nitrogen dioxide CNO2^
Hydrogen chloride (HCl)
Hydrogen fluoride (EIF)
Fatty acids .
Aldehydes ...
Esters
Slightly.
Slightly.
Very soluble.
Soluble.
Very soluble.
Soluble (short-chain).
Soluble.
Insoluble.
1 Abstracted from literature, cited in reference 8-
-------
control laboratory
ABSTRACT
THIS REPORT presents itemized lists of instrumen-
tation and laboratory equipment and their estimated
installed costs. This equipment was selected to permit
normal monitoring of plant operation and to aid in
the performance of tests for development of inciner-..
ator design and operating techniques. References to
existing test procedures are presented to aid in the
proper application of the equipment items suggested.
INTRODUCTION
CONTROL OF THE OPERATION of a modern continuous
feed incinerator plant requires instrumentation that
will indicate and record for the plant operators and
supervisors, the existing operating conditions and
any deviations from normal. Further development
of incinerator operating and design techniques will
be expedited by special laboratory equipment and
test facilities that will permit a complete investiga-
tion and evaluation of all of the variables of refuse
composition, furnace operation, flue gas conditions,
process water contamination, and residue com-
position.
The equipment required to instrument an inciner-
ator plant and equip laboratories for research and
development work has been divided into four
categories, as follows: Group I, indicating and
recording equipment for incinerator operation; group
II, physical laboratory equipment; group III, chemi-
cal laboratory equipment; and, group IV, monitoring
equipment for test and development studies.
An itemized list of equipment is presented for
each of these groups including estimates of installed
costs and space requirements.
SUMMARY AND RECOMMENDATIONS
The instruments listed in group I (indicating and
recording equipment for incinerator operation) are
essential to good plant operation and their installa-
tion is recommended in the proposed No. 5 Incinerator
plant for the District of Columbia.
The balance of the instruments and laboratory
equipment listed in this report have been selected
to permit complete analyses and testing of the inciner-
ator plant operation. There is currently a lack of
complete test data on municipal incinerator operation.
The installation of this equipment is recommended
so that complete test data can be obtained for use
in improving municipal incinerator practices. The
estimated costs for the various groups of equipment
installed, and the laboratory space, are listed in
table 37.
TABLE 37
ESTIMATED INSTALLED COSTS POR EQUIPMENT AND LABORATORY SPACE
Group
I
II
III
IV
Equipment and space
Indicating and recording for incinerator op-
Physical laboratory . . . .
Physical laboratory space
Chemical laboratory . .
Chemical laboratory space
Master control room for monitoring equip-
ment
Subtotal
Total cost of instrumentation and lab-
Cost
$158 000
11 900
22, 500
73 955
50,000
106 320
25 000
289, 675
447 675
GROUP I
Indicating and Recording Equipment for Incinerator
Operation
The operation of a conventional incinerator furnace
of modern continuous feed design can usefully employ
a more elaborate system of instrumentation than the
older batch feed type units. This additional equip-
ment is justified if the operation of the plant is to be
maintained at design conditions with optimum burn-
out of the refuse and minimum air pollution. The
29
-------
DAY & ZIMMERMANN
instruments tabulated below will monitor plant
operating conditions and sound alarms if operating
conditions deviate too far from normal or if potential
or actual equipment failure is indicated.
We recommend the installation of the following
indicating instruments on a control panel at each
furnace unit:
Installa-
Equip- tion, in-
mint list eluding
price overhead Total
Draft gages indicating pressures
(or drafts) of all air supply
systems, underfire air compart-
ments, furnace, air pollution
control equipment inlet and
outlet, induced draft fan inlet
and stack
Bourdon tube pressure gages for
water and compressed air
supplies to the unit
$1, 600 $2, 400
600
550 1,150
We recommend the installation of the following
indicating-recording instruments on the control
panel at each furnace unit:
Installa-
Equip- tion, in-
ment list eluding
price overhead Total
Smoke density recorder ........ $1, 590 $515 $2, 105
Temperature recorders for furnace
and stack temperatures ........ 1, 975 925 2, 900
Counter recorder for number of
buckets charged each furnace . . . 400 170 570
The following additional recorders should be pro-
vided for installation on a supervisor's panel:
Ambient air temperature
Wind speed and direction
The following indicating-recording-controlling
units are recommended for installation on the control
panel at each furnace unit:
Equip-
ment list
price
$630
i 2,500
Install-
tion, in-
cluding
overhead
$500
1,800
Total
$1, 330
4,300
Furnace draft recorder controller.
Flue gas temperature recorder
controller
Induced draft fan motor overload
controller
Remote airflow damper con-
troller .
Equip-
ment list
price
$2, 725
3,600
2,100
350
Install-
tion, in-
cluding
overhead
Total
$1, 275 $4, 000
2, 000 5, 600
650 2,750
350 700
We recommend the installation of multiple alarm
units including horns and lights for all of the critical
items in furnace operation where damage to equip-
ment or loss of production might occur if their
operating conditions change without notice. Fifteen
to twenty alarm points normally are monitored at
each furnace. Examples of such alarm points are
high and low furnace temperatures, high furnace
pressure (loss of furnace draft), high and low stack
temperatures, high ashpit temperature, high smoke
density, high cooling water temperatures, low water
pressure, high ampere loading of induced draft fan,
low compressed air pressure, and stoker failure.
Installa-
Equip- tion, in-
ment list eluding
price overhead Total
$700 $650 $1,350
Monitoring 15 alarm units for
each furnace
The installation of a total of six television cameras
and three monitors is recommended. One camera
would be in each of the four furnaces and two cameras
would be mounted on the charge floor. All monitors
would be located at the central control room.
Equip-
ment list
price
Six television cameras, including
air-cooled furnace housing, pro-
truding air-purged furnace
lenses, and water-cooled air
supply compressor $48, 000
Three 14-inch television monitors. 1, 670
Instal-
lation, in-
cluding
overhead Total
$9, 000 $56, 000
600 2, 270
It is estimated that the indicating and recording
equipment tabulated above for group I could be in-
stalled, piped, and wired on appropriate panels for
approximately $158,000 for a four-furnace plant.
GROUP II
Physical Laboratory Equipment
This section covers the equipment required for the
collection, sample preparation, and physical analyses
of samples of refuse, ash residue, fly ash, and furnace
slag.
We referred to ASTM Standard: D 271-64, Standard
Methods of Laboratory Sampling and Analysis of Coal and
Coke, for equipment selection and laboratory procedures
for refuse analysis (JL).
These ASTM procedures provide for the determina-
tion of moisture content, ash, volatile matter, fixed
carbon, sulphur, ash fusibility, ultimate analysis, and
-------
special studies for incinerators
31
heating value of coal and coke. They may be used as
a guide for the development of refuse test procedures
pending new standards developed specifically for in-
cinerator plant work. Chemical tests described are
covered in the group III equipment section of this
report.
The collection and size reduction of a composite
refuse sample is difficult to accomplish in a reproduci-
ble manner. Procedures similar to ASTM Standard
D 2013-65 T (2) may be followed; however, most test
operators resort to first separating a large sample of
refuse into each of its components. These components
are then individually weighed and analyzed and the
composite sample analysis determined by weighted
additions of the analyses of the individual components.
To analyze a typical composite refuse sample, the
following procedure would be employed: A refuse
sample representative of the furnace charge is spread
on tared (weighed) pans, weighed, and air dried at
room temperature, or in a special drying oven at 10°
C. to 15° C. above room temperature, and weighed
again. The drying is continued until the loss in weight
is not more than 0.1 percent per hour. The sample is
then put through an initial shredder and a final shred-
der to reduce the pieces of refuse to a much finer con-
sistency. A riffle sampler is used for homogenizing
and separating a larger sample into several similar
smaller ones.
Several different analyses are performed on these
smaller samples. A drying oven is used to determine
the weight percent of water and volatile matter, a
low temperature muffle furnace for weight percent
carbon and ash, and an adiabatic calorimeter for de-
termining the heat of combustion of any solid or liquid
material that can be completely burned in oxygen.
Instruments and equipment prices for physical
preparation and analysis of refuse, ash, and furnace
slag are based on the catalogs of scientific labora-
tory and industrial apparatus suppliers (3-5).
The equipment shown in table 38 is required for
refuse sample preparation and analysis.
The analysis of slag and flyash is desirable to de-
velop methods for the control of slag formation.
Samples should be checked for ash softening tempera-
ture and complete chemical composition. Detailed
procedures are outlined in ASTM Standard D 1857-64
T ((5) which may be used as a guide, pending develop-
ment of incinerator test standards. For slag and ash
sample preparation, the additional equipment shown
in table 39 is required.
TABLE 38
LABORATORY EQUIPMENT FOR REFUSE SAMPLE ANALYSIS
Initial shredder with heavy-duty
rotor blades driven by a 3-hp.
electric motor
Final shredder with }4-hp. elec-
tric motor
Scale having a 5-kg. capacity and
0.5-gm. sensitivity
Riffle sampler with stainless steel
hopper containing 24 chutes
with %" x 4.5" openings
Drying oven-mechanical convec-
tion, electric, up to 260° C.,
Low temperature electric muffle
furnace with self-contained
voltage input adjuster and
indicating pyrometer on the
panel, with a 1,200° C. range. . .
Analytical balance having a 160-
gm. capacity and 0.1-mg.
Desiccators, 4'glass vacuum type
Adiabatic oxygen bomb-type
calorimeter with electric water
Galvanized iron pans approxi-
mately 18" x 18" x 1 5"
Porcelain capsules with flat
Galvanized iron or tin can con-
tainers with air-tight friction
or screw tops with rubber
Equip-
ment
list
price
$550
930
100
145
430
160
770
55
1,280
15
10
30
Installa-
tion, in-
cluding
overhead
$400
90
100
100
Total
$95
1 02
1CX
14
53
26
77
5
1,281
1
1
3
TABLE 39
LABORATORY EQUIPMENT FOR SLAG AND ASH SAMPLE PREPARATION
Bandsaw with abrasive blade for
cutting samples to size
Power crusher with 2-hp. motor . .
Motor-driven pulverizer with 6"-
diameter grinding discs ..... .
Equip-
ment
list
price
$480
600
530
Installa-
tion, in-
cluding
overhead
$220
250
220
Total
$700
850
750
-------
32
DAY & ZIMMERMANN
For ash and slag softening temperature determina-
tions, the additional equipment shown in table 40
is required.
The equipment required for chemical analysis of
refuse, residue, ash, and slag is described in more
detail with the group III equipment of this report.
TABLE 40
LABORATORY EQUIPMENT FOR SLAG AND ASH TEMPERATURE
DETERMINATION
Brass cone molds suitable for
making ash cones %" in height
and 54" in width at each side
of the base
High temperature electric muffle
furnace with indicating pyrom-
eter controller and silicon car-
bide heating elements providing
uniform temperature to a maxi-
mum of 2,700° F
Equip-
ment
list
price
$25
1,350
Installa-
tion, in-
cluding
overhead
$200
Total
$25
1,550
In selecting equipment for flue gas sampling for
moisture concentration and particulates, gaseous and
soluble contaminants, we consulted the following
sources: A paper by Jacobs, Braverman, Hochheiser,
and Ettinger (7); a paper by F R. Rehm (
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special studies for incinerators
33
Solid samples collected with the above equipment
must be further checked for particle size distribution.
Equipment and procedures required for this are de-
scribed in more detail with the group III equipment
of this report.
It is estimated that the equipment tabulated for
group II of this report can be purchased and installed
for approximately $11,900.
Approximately 500 square feet of floor space would
be required for the installation of this equipment
including working space for physical tests. It is esti-
mated that the addition of this space to the incinerator
plant, complete with laboratory furniture, sinks,
closets, electrical lighting and power outlets, plumb-
ing fixtures, piping and air conditioning, would cost
$22,500.
GROUP III
Chemical Laboratory Equipment
This section covers equipment required for the
chemical analysis of samples collected or prepared
with the equipment listed under group II, physical
laboratory equipment.
Presented in this section is the chemical laboratory
equipment recommended for complete analysis of
refuse, slag, residue, fly ash, water, and flue gas. In
general, this equipment is of a more sophisticated
and delicate nature than that of the physical labora-
tory. Therefore, these two laboratories will be sepa-
rated from each other and any delicate equipment
usually used in physical testing will be located in
the chemical laboratory. Examples of such equipment
are the microscopic and photographic apparatus re-
quired for particulate determination of gas and water
samples.
Instrument and equipment costs were obtained from
the catalogs used for group II items, as well as direct
quotations from individual equipment manufacturers.
The ASME Test Code PTC 28-1965, (-Z2) and ASTM
Designation: Ell-61, (23) were referred to for equip-
ment for particulate analysis studies. Among the test
procedures described in these references are specific
gravity, particle size distribution, bulk electrical
resistivity, bulk density, and moisture content. The
equipment recommended for gas and water sample
particulate determinations is tabulated in table 42.
For equipment and methods used in refuse sample
ultimate analysis, reference was made to ASTM
Standard D 271-64 (f) and work by Etzel and Bell
(if). As previously reported, the procedures required
TABLE 42
LABORATORY EQUIPMENT FOR PARTICULATE DETERMINATIONS
Analytical balance having a 160-
gm. capacity and 0.1-mg.
sensitivity
Drying oven — mechanical convec-
tion, electric, up to 260° C.,
Set of 23 sieves of 8' ' diameter
recommended as International
(ISO) Standards ranging from
90.5 mm. to 44-0 mju
Electrical sieve shaker with }i
hp. motor and vibration regula-
Photobinocular microscope with
graduated mechanical stage,
continuously variable magni-
fication flat field achromatic
system, and high intensity
illuminator
Three interchangeable camera
accessories for the photobin-
ocular microscope :
3%" x4%" Polaroid filmpack .
4" x 5' ' platemaking camera . .
Scale having a 5-kg. capacity and
Chemical centrifuge with 7-step
speed control rheostat and
stainless steel basket and drain-
Filtering and dissolving porcelain
cone filter, case of 3 with 2-mm.
Turbidimeter with opal glass
light source, reflector adjust-
able slit, apertured mirror, and
specimen tube for measuring
suspended matter or colloids in
Le Chatelier flask for specific
gravity determination of partic-
Constant temperature water bath
with electric heating and
High-voltage conductivity cell
for determination of bulk elec-
trical resistivity with an 0 to
15 kv. voltage output at cur-
rents up to 1 milliampere
Equip-
ment
list
price
$770
430
270
700
1 080
110
150
100
485
30
355
25
300
500
Installa-
tion, in-
cluding
overhead
$100
Total
$770
530
270
700
1,080
175
110
150
100
485
30
355
25
300
500
289-620 O—68-
-------
DAY & ZIMMERMANN
TABLE 42—Continued
LABORATORY EQUIPMENT FOR PARTICULATE DETERMINATIONS Con.
TABLE 43
LABORATORY EQUIPMENT FOR REFUSE CHEMICAL ANALYSIS
Electric oven, temperature and
humidity controlled for con-
taining the high-voltage
conductivity cell
Desiccator (4) glass vacuum type
with desiccant
Combustion crucibles with covers
(6 with 20-milliliter-capacities
each) . .
Bahco micro particle size classifier.
Equip-
ment
list
price
$1,000
55
80
2,895
Installa-
tion, in-
cluding
overhead
200
Total
$1,000
55
80
3,095
to obtain a reproducible representative sample have
not been adequately developed and most operators
separate the refuse into individual components for
analysis. Further test work is recommended to develop
suitable refuse sampling and test procedures.
To determine the total percentages of carbon and
hydrogen present a sample is weighed and then burned
in a closed system with the products of combustion
being fixed in an absorption train after complete
oxidation and purification from interfering substances.
An automatic nitrogen analyzer was selected for
nitrogen concentration determination instead of
choosing apparatus for the wet chemical Kjeldahl-
Gunning method in order to decrease the analysis
time required and increase the accuracy of the results.
For sulfur analysis, an electric oxygen bomb type
apparatus is suggested. Samples are burned in an
atmosphere of compressed oxygen so that all hydro-
carbons are oxidized to carbon dioxide and water,
and all sulfur compounds are converted to sulfur
oxides. These oxides are absorbed in a water chamber
at the bottom of the bomb and standard quantitative
methods are then used to determine the amount of
sulfur present.
The equipment recommended for chemical analysis
of refuse samples is tabulated in table 43.
Chemical analysis of slag, ash, and water samples
can best be performed in a well equipped syectro-
graphic laboratory.
Work by Regis (J j) demonstrated that the analysis
of slag type materials by instrumental methods gives
the desired accuracy and requires a fraction of the
rime needed for analysis by wet chemical methods.
Automatic combustion unit with
3 electrically heated furnace
sections, individually con-
trolled and having a maximum
continuous furnace temperature
of950°C
Rate of flow meter and regulator. .
Water absorber, 2 required, both
containing solid dehydrating
reagent
Carbon dioxide absorber contain-
ing solid absorbing agent
Automatic nitrogen analyzer,
complete with thermometer,
100 aluminum combustion
boats, copper tubing assembly,
accessories, and chemical
reagents
Sulfur apparatus, double-valve,
oxygen-bomb type with water
bath, ignition unit, oxygen
connection, gages, valves, 6
stainless steel fuel capsules,
and 100 gelatin capsules
Equip-
ment
list
price
$1, 750
35
40
20
2,500
560
Installa-
tion, in-
cluding
overhead
Total
$1, 750
35
40
20
2,500
560
Characteristic K alpha radiation was used in the
spectrograph to analyze incinerator slag samples of
diverse chemical compositions for A12O3, SiO3, K2O,
CaO, P2O6, Fe2O3, TiO2 and ZnO. Determination of
lighter elements such as chlorine, phosphorus, sulfur,
and bromine is now possible due to recent technological
improvements.
The vacuum x-ray type of spectrograph is more
applicable for analyzing compounds of higher con-
centration in a specific sample while the arc emission
type of spectrograph gives more accurate analysis of
trace quantities. The former of these types is more
desirable for the present application.
It is estimated that a complete installed vacuum
x-ray spectrographic laboratory consisting of a sample
grinder, sample hydraulic press, sample pellet dies,
power source unit, vacuum spectrograph x-ray tube
system, electronic direct reading detector, and film
diffraction study facilities would cost $40,000.
A series of wet testing procedures for ash residue
analysis by the Drexel Institute of Technology's en-
-------
special studies for incinerators
35
vironmental engineering department were also re-
viewed for determinations not applicable to x-ray
spectrographic analysis (16).
The method for determining the lipid concentration
where lipids are defined as "any of various substances
including fats, waxes, phosphatides, cerebrosides, and
related or derived compounds that with proteins and
carbohydrates constitute the principal structural com-
ponents of living cells" was used in specifying the
following testing equipment.
Equip-
ment list
price
Soxhlet extraction apparatus sup-
plied with condenser, extrac-
tion tube, and flask (per case
of 2) $55 ...
Multiple unit hotplate 120 . . .
Extraction thimbles (per box of
25) 10 ...
Installa-
tion, in-
cluding
overhead Total
$55
120
10
Numerous biological and chemical water sample
analyses are defined in the Betz handbook (17~).
Additional water testing procedures are suggested
with the necessary laboratory equipment in the 1966
Book of ASTM Standards (!
-------
DAY & ZIMMERMANN
TABLE 44
AUXILIARY LABORATORY EQUIPMENT
Extraction apparatus, ASTM-
Undcrwriter's model, electric,
6 unit complete outfit with six
400-milliliter flasks, 6 siphon
tubes, and neoprene tubing ... .
Combination hotplate and
magnetic stirrer
Titration lamp
Hygrometer, motor ventilated
Motor-driven rotary pump
Precision wet-test gas meter
Constant voltage transformer
Voltmeter
Ammeter
Galvanometer
Potentiometer (portable, thermo-
couple type)
Assorted laboratory hardware,
tools, glassware, and imple-
ments such as various con-
tainers, stoppers, rubber tubing,
Bunsen burners, thermometers,
spatules, etc
Chemicals in solid, reagent, and
gaseous form required for
sample analysis testing as well
as those used in ordinary
laboratory procedures such as
glassware cleaning
Equip-
ment
list
price
$420
95
30
80
80
375
35
95
30
75
300
2,000
2,000
Installa-
tion, in-
cluding
overhead
Total
$420
95
30
80
80
375
35
95
30
75
300
2,000
2,000
It is estimated that the addition of this space to the
incinerator plant, complete with laboratory furniture,
sinks, storage cabinets, electrical lighting and power
outlets, plumbing fixtures, piping, and air condition-
ing, would cost $50,000.
GROUP IV
Monitoring Equipment for Test and Development Studies
This section covers the additional monitoring equip-
ment recommended for continuous indication and re-
cording of the operating conditions of a single
incinerator furnace unit. The present lack of operating
data seriously hinders the development of adequate
incineration facilities. It is intended that the following
equipment would be used to evaluate all of the vari-
ables of incinerator operation so that improvements
could be recommended in incinerator design and
operating practices.
The instruments tabulated for this section would
be installed on a panel in a monitoring room where
facilities would permit analysis of the recorded data.
Control of the operation of the incinerator unit would
remain at the panel provided for the group I instru-
ments .
The primary variables to be recorded are the condi-
tions of combustion air, furnace, flue gas, and process
water.
The analyses of data from these records combined
with analyses of refuse and residue will permit a
determination of the effect of changes in operating
conditions on overall incinerator performance.
Tables 45 and 46 show recommended equipment for
recording of the above variables.
TABLE 45
MONITORING EQUIPMENT
Measurements
Combustion air:
Underfire air and overfire
air flow recorders with
special duct work arrange-
ments for flow measure-
ments . .
Temperature recorder (12
positions) for underfire,
wall cooling, and overfire
air
Pressure recorders for draft
and pressures in air zones,
also including furnace, dust
control equipment, and
stack conditions
Forced draft fan motor current
recorder
Furnace:
Refuse feed rate recorder
Temperature recorder 24 point
with chromel-alumel
thermocouples for refractory
temperatures to 2,000° F . . .
Temperature recorder 24 point
with platinum-rhodium
thermocouple for refractory
and face temperatures to
2,700° F
Temperature recorder 6 point
with radiamatic elements
in silaramic tubes for gas
temperature measurements .
Equip-
ment list
price
$9, 200
1,660
9,800
1, 975
1,340
2,675
3,275
3,275
Installa-
tion, in-
cluding
overhead
$10, 000
1,600
2,400
500
760
2,400
2,400
1,800
Total
$19, 200
3,260
12,200
1,740
2,100
5,075
5,675
5,075
-------
special studies for incinerators
37
TABLE 46
MONITORING EQUIPMENT
Measurements
Flue gas :
Flue gas flow rate recorder ....
Carbon dioxide analyzer and
recorder
Oxygen analyzer and recorder .
Water vapor concentration
recorder with infrared
sampling and conditioning
equipment
Stack emission participate
loading recorder including
continuous sampling
system - •
Temperature recorder, 24-point,
1-1 point with chromel-
alumel thermocouples
Process water:
Water flow rate recorder
pH analyzer and recorder
2 points
Temperature recorder 6 point .
Turbidity recorder with
flow chamber, light source
and transmitter
Equip-
ment list
price
$1, 090
2,200
3,000
3,500
10,000
2,765
2,100
2, 875
1,655
1, 800
Installa-
tion, in-
cluding
overhead
$2,000
1,800
2,000
2,700
5,000
2,400
1,500
1,500
1,000
1,200
Total
$3, 090
4,000
5,000
6, 200
15, 000
5,075
3,600
4,375
2,655
3,000
This equipment in conjunction with the recording
equipment of group I would provide for monitoring
of the variables of operation of a single incinerator
furnace unit.
The approximate purchased and installed cost for
the group IV equipment of this report is $106,320.
Approximately 800 square feet of floor space would
be required for the installation of the panels housing
this recording equipment, including space for desks,
reference tables, and storage cabinets for charts and
supplies. It is estimated that the addition of this
space to the incinerator plant, complete with office
furniture, electric lighting, utility outlets, and air
conditioning, would cost $25,000.
The operation and maintenance of this laboratory
equipment will require specially trained personnel.
The number of people employed will vary with the
test schedules. It is assumed that a large percentage
of the test work conducted with this equipment
would be handled under research grants to colleges
and universities.
REFERENCES
C?) AMERICAN SOCIETY FOR TESTING MATERIALS.
Designation: D 271-64; standard methods of
laboratory sampling and analysis of coal and
coke. Revised 1964.
(2) AMERICAN SOCIETY FOR TESTING MATERIALS.
Designation: D 2013-65 T; method of pre-
paring coal samples for analysis (tentative).
(3) FISHER SCIENTIFIC Co. Modem laboratory appli-
ances catalog. Pittsburgh, Fisher Scientific Co.,
1963.
00 E. H. SARGENT AND Co. Scientific laboratory in-
struments, apparatus, supplies and chemicals cata-
log. Chicago, E. H. Sargent and Co., 1964.
(5) ARTHUR H. THOMAS Co. Scientific apparatus and
reagents catalog. Philadelphia, Arthur H.Thomas
Co., 1965.
(6) AMERICAN SOCIETY FOR TESTING MATERIALS.
Designation: D 1857-64 T; test for fusibility
of coal ash (tentative).
(7) JACOBS, M. B., M. M. BRAVERMAN, S. HOCH-
HEISER, and I. ETTINGER. Sampling and anal-
ysis of incinerator flue gases. Presented at the
Air Pollution Control Association 51st Annual
Meeting, Philadelphia, May 25-29, 1958. p.
7-1, 7-11.
(£) REHM, F. R. Test methods for determining
emission characteristics of incinerators; in-
formative report No. 2. Journal of the Air Pollu-
tion Control Association, 15(3): 127-135, Mar.
1965.
(9) AMERICAN SOCIETY MECHANICAL ENGINEERS. Test
Codes PTC 21-1941; dust separating apparatus.
(.ZO) AMERICAN SOCIETY MECHANICAL ENGINEERS. Test
Codes PTC 27-1957; determining dust con-
centration in a gas stream.
(11) WESTERN PRECIPITATION CORPORATION. Methods
for the determination of velocity, volume, dust and
mist content of gases. 4th ed. Los Angeles,
Western Precipitation Corp., 1951.
(i2) AMERICAN SOCIETY MECHANICAL ENGINEERS.
Test Codes PTC 28-1965; determining the prop-
erties of fine particulate matter.
(_Z3) AMERICAN SOCIETY FOR TESTING MATERIALS.
Designation: E 11-61; standard specifications
sieves for testing purposes.
(If) ETZEL, J. E., and J. M. BELL. Methods of sam-
pling and analyzing refuse. APWA Reporter,
29(11): 2-4, 18-21, Nov. 1962.
-------
3S
DAY & ZIMMERMANN
(.0") REGIS, A. J. X-ray spectrographic analysis of
incinerator slags. In Proceedings, 1966 Na-
tional Incinerator Conference, American
Society Mechanical Engineers, New York,
May 1-4, 1966. p. 195-198.
(_16~) ENVIRONMENTAL ENGINEERING DEPARTMENT,
DREXEL INSTITUTE OF TECHNOLOGY. Inciner-
ator ash residue testing procedures for the
analysis of moisture content, volatile matter,
ash content, gross calorific value, sulfur, ni-
trogen, lipids, carbon, hydrogen, phosphorus
(PjOj), and potassium (K^O).
(i7) BETZ LABORATORIES, INC. Bet% handbook of in-
dustrial water conditioning, 6th ed. Philadelphia,
Betz Laboratories, Inc., 1962. 425 pp.
(If) AMERICAN SOCIETY FOR TESTING MATERIALS.
Industrial water, atmospheric analysis. Part 23.
In Standards. Philadelphia, American Society
for Testing Materials, 1966.
(^19~) AMERICAN SOCIETY FOR TESTING MATERIALS.
Designation: D 2329-65 T; tentative method
of test for biochemical oxygen demand of in-
dustrial water and industrial waste water
(tentative). 1965.
BIBLIOGRAPHY
PUBLIC HEALTH SERVICE. Selected methods for the
measurement of air pollutants. Washington, U.S.
Department of Health, Education, and Welfare,
1965.
MANUFACTURING CHEMISTS' ASSOCIATION, INC. Water
-pollution abatement manual; organisation and method
for investigating wastes in relation to water -pollution.
Manual W-l. Washington, Manufacturing Chem-
ists' Association, Inc., 1954, 7 p.
MANUFACTURING CHEMISTS' ASSOCIATION, INC. Water
pollution abatement manual; insoluble and undissolved
substances. Manual W-2. Washington, Manufactur-
ing Chemists' Association, Inc., 1949. 10 p.
MANUFACTURING CHEMISTS' ASSOCIATION, INC. Water
-pollution abatement manual; oils and tars. Washing-
ton, Manufacturing Chemists' Association, Inc.,
1955.
MANUFACTURING CHEMISTS' ASSOCIATION, INC. Water
•pollution abatement manual; neutralisation of acidic
and alkaline -plant effluents. Manual W-3- Washing-
ton, Manufacturing Chemists' Association, Inc.,
1960. 13 p.
ECKENFELDER, W. W. Industrial water pollution control.
New York, McGraw-Hill Publishers, 1966. 275 pp.
STERN, A. C. Air pollution. 2v. New York, Academic
Press, 1962.
AMERICAN SOCIETY FOR TESTING MATERIALS. Manual
on industrial water. Philadelphia, American Society
for Testing Materials, 1953. 336 p.
Low, M. J. D. Subtler infrared spectroscopy. Inter-
national Science and Technology, 62(2): 52-58,
Feb. 1967.
STEYERMARK, A. S. Quantitative organic microanalysis.
Philadelphia, Blakiston Company Publishers, 1951.
389 p.
KAISER, E. R. Chemical analysis of refuse compo-
nents. In Proceedings, 1966 National Incinerator
Conference, American Society Mechanical
Engineers, New York, May 1-4, 1966. p. 84-88.
CERNIGLIA, V J. Closed-circuit television and its
application in municipal incineration. In Proceed-
ings, 1966 National Incinerator Conference,
American Society Mechanical Engineers, New
York, May 1-4, 1966. p. 187-190.
HERBERT, D. B. The nature of incinerator slags.
In Proceedings, 1966 National Incinerator Con-
ference, American Society Mechanical Engineers,
New York, May 1-4, 1966. p. 191-194.
WOODRUFF, P. H., and A. W WENE. General over-
all approach to industrial incineration. In Proceed-
ings, 1966 National Incinerator Conference,
American Society Mechanical Engineers New
York, May 1-4, 1966. p. 219-225.
GODER, R., and A. MARSHALLA. Incinerator testing
programs, 1966. In Proceedings, 1966 National
Incinerator Conference, American Society Mechan-
ical Engineers, New York, May 1-4, 1966. p.
231-234.
ZINN, R. E. Progress in municipal incineration
through process engineering. In Proceedings, 1966
National Incinerator Conference, American Society
Mechanical Engineers, New York, May 1-4, 1966.
p. 259-266.
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size reduction
OF OVERSIZE BURNABLE WASTE
ABSTRACT
DISPOSAL of oversize burnable waste in the District
of Columbia is presently conducted by direct burial
or burning of these large objects in landfill operations.
The incineration of these objects directly in the fur-
naces with normal municipal refuse does not produce
acceptable burnout. The investigation of methods for
size reduction of these objects to pieces that will
burn compatibly with normal municipal refuse is
described. An alternate method of disposal by burning
dense objects in specially designed incinerators is also
described. The installation of a shredder for size
reduction is recommended.
INTRODUCTION
THE DEPARTMENT OF SANITARY ENGINEERING in
Washington, D.C., must provide a means to dispose
of oversize burnable waste collected from the residents
and industry which cannot be burned satisfacto-
rily with normal household refuse in municipal
incinerators.
Disposal of this material can be accomplished by
open dump burning, by direct burial in landfill opera-
tions, by size reduction to permit burning in inciner-
ator furnaces with normal household refuse, or by
burning in bulk form in specially designed incinerator
furnaces.
Good practice in dump operations or landfill rules
against disposal by open burning or direct burial in
landfill. We have been requested to study methods of
size reduction of this oversize burnable waste to permit
incineration with normal household refuse in the
proposed Incinerator No. 5.
Our studies indicate that disposal of some objects,
such as large tree stumps, by size reduction for in-
cineration is not always possible. This report therefore
includes discussions of both size reduction and special
burning equipment.
SUMMARY AND RECOMMENDATIONS
The disposal of oversize burnable waste in landfill
operations or by open dump burning is not acceptable
in today's society because of rodent problems, land
settlement, and air pollution resulting from these
activities.
This material can be burned in specially designed
incinerators or it can be shredded and mixed with
municipal refuse for burning in a conventional refuse
incinerator. The shredding of most objects presents
no unusual problems, however, certain dense objects
such as large tree stumps require special handling as
present-day shredders cannot satisfactorily handle
them.
Two methods of disposing of large tree stumps or
other dense objects are proposed. One method is to
burn them in a special incinerator. The second method
uses a special machine for splitting the stumps in the
ground for removal in pieces which can be hand-
loaded into a truck. Both of these disposal methods
are currently in use.
We recommend that there be installed at the
proposed No. 5 Incinerator plant a large shredder of
the hammermill type with grate bars selected to
discharge a product approximately 1" x 8" x 6" in
maximum dimensions. This unit is estimated to cost
$667,000 to install and approximately $125,000 per
year to own and operate. The ability of this unit to
also handle bulky metal objects will climate the need
for installation of a metal press at this site. Separation
of ferrous metal from the output of the shredder,
therefore, is included in this estimate as passage of
excess metal through the furnace is not recommended.
Availability of mobile stump splitters in the
Washington, D.C., area should permit the enforce-
ment of regulations which would require that all
tree stumps be delivered to the disposal plants in
pieces suitable for charging into this shredder.
39
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DAY & ZIMMERMANN
The use of a special bulky refuse incinerator does
not appear to be justified where the shredder applica-
tion can be employed. For comparison, the installed
cost of a bulky refuse incinerator is estimated at
$532,000, with annual operating costs of $104,000,
including an independent air pollution control system.
The use of the main incinerator furnace flues and fly
ash control equipment for the products of combustion
from a bulky refuse burner is not recommended where
strict air pollution requirements exist.
TYPES OF OVERSIZE BURNABLE WASTE
The refuse collection units of the Division of
Sanitation collect substantial quantites of oversize
burnable waste which cannot be acceptably mixed
with household refuse. These collections include such
items as: rubber tires—passenger and ofF-the-road
types; Christmas trees, brush, branches; overstuffed
and wood furniture; demolition lumber, logs, poles;
boxes, crates, pallets and skids; bundles of paper and
cardboard; mattresses.
In addition, the District employees remove and
must dispose of approximately 6,000 tree stumps
annually, having an average trunk diameter of 32 to
34 inches.
The above listing does not include bulky metal
objects such as refrigerators, washing machines, and
stoves. The handling of bulky metal objects for
disposal is discussed in the following section entitled
Sine Reduction of Bulky Metal Objects by Compression
Presses. These objects can also be shredded in equip-
ment suitable for size reduction of oversize burnable
waste as discussed in this report.
DISPOSAL METHODS
Disposal of oversize burnable waste by open burning
creates a public nuisance and seriously adds to air
pollution problems in the area of burning. Direct
burial of these objects in landfill operations consumes
landfill space at a rapid rate. It also tends to create
voids in the landfill which can harbor rodents and
vermin. The ultimate decomposition or decay of the
burnable material allows landfill settlement to occur
over extended periods of time, thereby reducing the
value of the landfill for future development, even for
use as park areas.
Two alternatives for disposal of oversize burnable
waste are considered in this report. The first method
consists of size reduction by shredding in specially
designed size reduction equipment to permit incinera-
tion in furnaces designed for the burning of normal
municipal refuse. The second disposal method consists
of burning the bulky objects in a specially designed
incinerator that will permit the objects to remain in
the furnace atmosphere until complete burnout is
obtained. This furnace must necessarily be equipped
with adequate air pollution control equipment.
Equipment required for destruction of oversize
burnable waste by shredding followed by normal in-
cineration; or, by direct burning without size reduc-
tion in specially designed incinerators; has been in
operation in this country for several years. Both
methods have operating limitations which are dis-
cussed in further detail in the following sections of
this report.
EQUIPMENT FOR SHREDDNG
The preparation of oversize burnable waste for de-
struction in a conventional refuse incinerator requires
a reduction in size to pieces that will be completely
consumed in the incinerator furnace.
Several types of shredding equipment are available
for the size reduction of those objects listed in the
section of this report, "Types of Oversize Burnable
Waste." None of the units investigated, however,
could process all of those items listed to an acceptable
end product without certain operating limitations.
Three types of mills were investigated for this shred-
ding application. These are as follows: Impact mills;
hammermills with grates; and knife hogs. The princi-
pal features and performance of these mills are de-
scribed as follows.
Impact Mills
Impact mills reduce the size of bulky objects by
the action of projections on a rotating mandrel (or
cylinder) tearing away pieces of the charged object
(fig. 4). A further reduction in the size of these pieces
is obtained by multiple impact between anvils in the
outer case of the machine and the projections on the
mandrel. The anvils are normally spring-loaded to
permit automatic release so that large dense objects
will not wedge in the machine and jam its action.
Impact mills do not have any grates to control the
size of the discharged material. As a result most of
the material entering the machine is discharged after
traveling approximately one-half the distance around
the inside perimeter of the unit. This results in a wide
variation in dimensional characteristics of the dis-
charged material. Some objects such as rubber tires,
mattresses, and cushions may pass through the ma-
chine with only a partial reduction in size.
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special studies for incinerators
41
FRONT IMPACT
MECHANISM
REAR IMPACT
MECHANISM
INLET CHUTE
ROTOR
FIG. 4. Schematic arrangement of an impact mill.
Hammermills with Grates
Hammermills with grates reduce the size of bulky
objects by the action of floating "hammers" which
are rotated within the case at relatively high velocity
(fig. 5). These hammers tear away pieces of the
charged object and constantly strike against these
pieces as they rotate within the machinery case until
the pieces are sufficiently reduced in size to pass
through the grate openings. This type of machine
has a limitation on the size reduction that can be
accomplished in a single pass at maximum rated ca-
pacity. Suitable size reduction can be obtained at
reduced capacities or by operating machines in series
to effect a two-stage size reduction.
INLET
SWINGING
HAMMERS
GRATE BARS
-DISCHARGE
FIG. 5- Schematic arrangement of a hammermill.
Knife Hog
The knife hog has a rotating mandrel with sharp
edged blades which shave away pieces of the charged
object and discharge them at the far side of the ma-
chine (fig. 6). Some units are provided with internal
blades fixed in the perimeter of the machine case and
meshing with blades on the rotating mandrel to pro-
vide a punching or shearing action for further size
reduction of the shaved pieces. This type of unit
cannot accept any objects containing metal without
possibility of damage to the knives or blades.
FEED OPENING
FIXED BLADES
KNIFE BLADE
ROTOR
-DISCHARGE
OPENING
FIG. 6. Schematic arrangement of a knife hog.
MACHINE LIMITATIONS
A review of the above machines indicates the
following limitations must be considered: Rubber tires
can be reduced in a hammermill with grates if the
size and horsepower of the machine are adequate.
Removal of the wire bead before shredding is common
commercial practice. Tires may pass through an im-
pact mill with only limited size reduction. The wire
bead of the tires will damage knife hogs. Tree stumps
of larger sizes are beyond the capacity of present day
shredding equipment. Smaller sizes or pieces of stumps
can be splintered in a hammermill or impact mill.
Demolition lumber can be processed in a hammermill
or impact mill. The maximum length of timber is
normally limited to 6 feet for moderately powered
machines. The initial size reduction may produce
pieces up to 4" in thickness depending upon the
specific design of the machine. In these cases a second
stage of size reduction will be required to limit the
maximum size to the dimensions specified above.
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DAY & ZIMMERMANN
Mattresses and springs are handled best by the hammer-
mill. Size reduction of these objects in an impact mill
is not consistent. Bulky metal objects can be processed
in the impact or hammermills for size reduction and
shredding. Equipment selected for this type of opera-
tion is currently being used to replace hydraulic presses
where metal recovery is a consideration.
EFFECTS OF SHREDDED MATERIAL ON FURNACE
OPERATIONS
Combustible refuse to be burned in a conventional
incinerator furnace must be reduced in size to pieces
that can be fully incinerated within the time the
material is allowed to remain in the furnace.
The normal retention time in a modern continuous
feed incinerator furnace ranges from 30 to 45 minutes
depending upon design conditions. It is our opinion
that combustible material must be reduced to less than
1 inch in thickness to ensure acceptable burnout
when fired with conventional refuse. The thickness
of the combustible material is considered critical.
Length and width dimensions should not exceed 8"
x 2", although these are not critical. This size spec-
ification should assure the optimum burnout in the
furnace of the more dense components. Unfortunately,
reduction to this maximum size will produce an
abundance of smaller pieces. Precautions must be
taken to distribute the shredder discharge product
throughout the other refuse being burned to prevent
charging the furnace with a homogeneous mass of
particles that will obstruct airflow through the
burning materials.
Metallic objects discharged from a shredder may
be mixed with the combustible refuse to be burned on
an incinerator stoker. In some cases, these pieces of
metal may cause trouble on a continuous feed stoker.
The smaller pieces of metal and wire may wedge into
or clog air openings in the grate. The sharp edges of
some larger pieces can be forced by the grate action
against the refractory surfaces with possible resultant
damage to the refractory.
The destruction of large quantities of bulky metal
objects in a shredder for feed to a continuous feed
stoker furnace should not be considered at this time.
Where a shredder is installed for destruction of a
mixture of oversize burnable waste and bulky metal
objects, a magnetic separator should be installed to
remove ferrous metal from the product prior to its
entry into the furnace units.
The impact mill and hammermill are capable of
shredding household appliance types of bulky metal
objects. Continuous feed of large quantities of metal
from the destruction of these objects however, may
result in high stoker and furnace maintenance costs
for the reasons stated previously. Additional research
at the operating level is required to evaluate fully the
aspect of incineration of shredded metal objects with
refuse.
INCINERATORS FOR BURNING BULKY OBJECTS
The investigation into suitable methods for disp osal
of the large tree stumps covered several alternate
procedures including the possibility of splitting the
stumps for ultimate size reduction in a shredder as
described later in this report. An alternative to s plit-
ting the stumps is a reduction by burning in a special
incinerator designed for the destruction of this type
of material. Several bulky object incinerators are
presently in service in this country and some research
studies are being conducted into their operation (_1~).
These units operate on a batch feed basis. They are
constructed with refractory walls and roof arches
which help to hold temperatures in the furnace at the
high levels necessary to maintain ignition for burning
through heavy timbers, logs, and tree stumps. Less
dense objects, such as furniture, mattresses, and auto-
mobile tires are used as tinder for the ignition of these
units.
It is anticipated that large tree stumps would be
charged into the furnace about every 2 hours during
the day shift and then be allowed to burn down over-
night. Ash would be removed from the furnace once
a day before the initial charge. Metallic residue from
from the bulky waste would be removed with the ash.
This metal is normally in an annealed condition and
should present no problems for disposal in a landfill.
Refuse is charged into furnaces of this type with a
front-end loader provided with a removable extended
pusher blade. The same unit, with the blade removed,
is used for ash removal. A crew of three to four men is
normally provided during the brief periods of time
required for charging and ash removal operations.
Periodic checking during burn-down cycles will re-
quire the parttime services of one man.
Air pollution from a bulky refuse incinerator could
become a problem if no control equipment is provided.
As reported in the first section of this report, the prod-
ucts of combustion of automobile tires and from
some of the organic constituents of the tree stumps
may require control. The installation of wet scrubber
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special studies for incinerators
43
type of air pollution control equipment to remove
both particulate matter and soluble gaseous products
of combustion should be provided for this type of
incinerator. A vapor plume will exist under certain
operating conditions.
The design of a bulky refuse burner would be gen-
erally as shown in figure 7. Adequate provision must
be made for burnout of the volatile matter and partic-
ulates before the hot gas stream is quenched prior
to its entry into the associated air pollution control
equipment. A study would be required to determine
the need for auxiliary firing into the secondary com-
bustion chamber as an aid to ensure complete burnout.
The need for this auxiliary firing will depend upon
the type of material burned and the arrangement of
the flues. Certain types of bulky refuse may also re-
quire auxiliary firing in the main combustion chamber.
EQUIPMENT FOR SPLITTING TREE STUMPS
The inability of the size reduction equipment
investigated to handle stumps from large size trees
required an investigation into possible methods of
splitting these stumps into pieces that would be
acceptable to shredding equipment. This investiga-
tion covered procedures including blasting, sawing,
and splitting with large hydraulically operated
wedge presses. None of these procedures was con-
sidered acceptable because of maintenance, noise and/
or stump handling difficulties.
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FLOODED
PLATE
SCRUBBER
SECONDARY
COMBUSTION
CHAMBER
INDUCED
DRAFT
FAN
SETTLING
CHAMBER
ELEVATION
FIG. 1. Schematic arrangement of a bulky refuse burner with wet scrubber for flue gas.
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4-1
DAY & ZIMMERMANN
One item of commercially available equipment (2)
was investigated which is known to remove stumps
from the ground in pieces small enough to be pro-
cessed in a shredder for final burning in an incinerator.
This unit is designed for installation on a crawler
shovel or large rubber-tired crane. It operates by
pulling a large shaped blade through the ground
and stump, cutting the stump and roots into pieces
which can be hand loaded into a truck.
The designer of this equipment has proposed that
he build a similar unit to split stumps that have
been removed intact from the ground. This unit
would operate by driving a blade down into the
stump with a vertical blow. Splitting of the stumps
after removal from the ground at a central location
would result in a local noise problem as impact of
the blade into the stump would be a major factor
in the success of this operation. Maintenance of the
yard in which this activity is conducted would also
be a consideration.
These units have the mobility to move from stump
to stump and therefore reduce stump handling prob-
lems that would be encountered with other methods
considered. The availability of such equipment makes
it possible for a municipality to require that stumps
be delivered to the disposal sites in pieces small
enough for further destruction by a shredder.
CAPITAL AND OPERATING COSTS
Shredder Installation
A shredder installation for size reduction of over-
size burnable waste should consist of shredding
equipment of adequate capacity to handle the most
difficult object anticipated plus necessary feed and
discharge conveyors. The shredder should have a
feed opening approximately 80 inches long by 48
inches high.
The installation should be capable of reducing
the size of both the combustible components making
up the majority of the feed and the incidental metal
attachments, fasteners, and inclusions. Motor require-
ments for the shredder will range from 300 to 1,000
hp., depending upon the specific unit selected. In
specifying the unit it is important that the manu-
facturer be advised of the range of material to be
processed so that the proper grate size and motor
horsepower can be provided. Shredding of bulky
metal objects in addition to the oversize burnable
waste will affect the selection of the equipment.
The associated materials handling equipment should
include a feeder to discharge into the loading hopper
of the shredder. Safety screens are necessary to prevent
injury to workers in the area from flying objects
ejected from the charge hopper by action of the
hammers in the shredder.
The discharge from the shredder should be conveyed
to a storage bin at the tipping floor level. Magnetic
separation is desirable in this conveyor assembly to
discharge ferrous material into a separate bin. The
combustible material can be removed from the storage
bin and loaded into the refuse bins by a front-end
loader. This is considered the most practical method
of distributing the shredded material throughout the
balance of the refuse. The alternate use of the
plant cranes, belt conveyors, and pneumatic conveyors
for distribution of the shredded material was investi-
gated but the front-end loader appears to provide the
best flexibility of operation at minimum operating and
maintenance costs.
The ferrous material can be loaded into trucks for
sale to metal dealers or it can be trucked to the disposal
site and buried with the ash residue from the furnaces.
We estimate the installed cost of this equipment in
a location adjacent to the tipping floor and refuse
pit would be approximately $667,000. This estimate
includes the foundations for the shredder and asso-
ciated equipment.
The estimate also includes special dust control
equipment, a motor ventilation system, and provisions
for sound attenuation of the noise generated by the
shredder. It does not include the architectural housing
over the equipment which is considered part of the
main incinerator plant.
The operation of the shredder would normally be
scheduled for the day shift. It is anticipated that this
activity would require the services of a machine oper-
ator and three laborers. Electric power and mainte-
nance would add to the total annual operating costs.
The following is a summary of the estimated capital
investment and annual costs for operation of a shredder
designed to handle oversize burnable waste and bulky
metal objects.
Bulky Refuse Incinerator
A bulky refuse incinerator for direct burning of
oversize burnable objects including larger tree stumps
would be constructed as shown in the schematic ar-
rangement drawing figure 4. The furnace would be
constructed with a refractory hearth and refractory
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special studies for incinerators
45
TABLE 47
SUMMARY OF ESTIMATED CAPITAL INVESTMENT AND ANNUAL COST
Capital investment :
Foundations and concrete work
Purchased equipment costs including delivery
Installation costs including electrical
Installed cost of physical equipment
Engineering and field supervision
Contingency
Escalation to December 1968
Total estimated project cost
Operating cost:
Maintenance
Annual fixed charges 15 years at 4^2 percent
Total annual owning and operating cost
Cost
$134 700
248, 300
138 800
25 000
546 800
39 200
54 000
27 000
667,000
30 000
25 000
8,000
63 000
62,000
125, 000
walls and roof arches from the charging doors to the
wet scrubber. The furnace would be designed with
mechanically operated full opening doors. It would
be charged by means of a mobile front-end loader
with pusher blade attachment to push the bulk mate-
rial into the furnace. The unit would be complete
with both forced and induced draft fans and a wet
scrubber for air pollution control.
It is estimated that a unit of this type will burn
approximately 16 pounds of waste wood products
per hour per square foot of hearth area (3). The unit
shown would average about 8,800 pounds per hour
capability of bulky burnable material.
This unit could be installed in the service yard at
the rear of the incinerator plant using the wet scrubber
as included in the following estimate, or the scrubber
could be eliminated and the hot gases directed into
the exit flue from one of the incinerator furnaces.
The use of the main incinerator furnace flues would
require that the capacity of the furnace affected, be
reduced by the equivalent of the material being burned
in the bulky refuse incinerator. This would require
one-half capacity operation of the incinerator furnace
for units of the size being considered, a procedure
that is not recommended, as reduced capacity opera-
tion is not readily obtainable without operating diffi-
culties such as burn-back into charge hoppers of the
refuse furnace.
A second alternative is to increase the size of the
air pollution control equipment of the furnace affected
to permit it to handle approximately 50 percent more
gas volume. This arrangement will affect the effi-
ciency of the air pollution control equipment which
is to some extent proportional to the gas velocities
through the equipment. It will also present some
operating problems in the control of the induced
draft equipment to maintain balanced operation be-
tween the two units.
A preliminary review of capital costs does not in-
dicate any substantial savings would be obtained in
passing the flue gas from the bulky refuse incinerator
through oversized air .pollution control equipment of
one of the main incinerator furnaces.
The following is a summary of the estimated capital
investment and annual costs for operation of a bulky
refuse incinerator with independent air pollution
control equipment. The estimate is based on the use
of a stub steel stack for discharge of the products of
combustion. The estimate includes subsurface founda-
tions, architectural treatment of the furnace enclosure,
necessary river water piping, a settling basin for fly
ash removal, and the river water intake structure
and pumps.
Capital Investment
General building, foundation and concrete work $68, 750
Purchased equipment delivered to site 152,100
Mechanical installation and refractory work 199, 300
Electric light and power 16, 250
Installed cost of physical equipment 436, 400
Engineering and field supervision 30, 600
Contingencies 43, 600
Escalation to December 1968 21, 800
Total estimated project cost 532, 400
Operating labor required to charge the furnace
and remove ashes would be assigned on a part time
basis during the day shift with periodic inspection
during the night shifts. It is estimated that total
labor costs on the part time basis would be $31,600
per year including supervision, labor, and a machine
operator. The total annual owning and operating
costs would be as follows:
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- DAY & ZIMMERMANN
Operating Costs REFERENCES
Labor $31, 600 (l~) KAISER, E. R. The incineration of bulky refuse.
Electric power 12,900 In Proceedings, 1966 National Incinerator
Maintenance 10, ooo Conference, American Society Mechanical
Engineers, New York, May 1-4, 1966. p.
Total direct operating costs 54,500 39^48.
Annual fixed charges, 15 years at 4>2 percent 49,500 (2) Private communication, BleS Stump Axe Co.,
Tyson's Corner, McLean, Va.
Total annual owning and operating costs .. . 104, ooo (3) Private communication, E. R. Kaiser, November
1966.
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size reduction of bulky metal objects
BY COMPRESSION PRESSES
ABSTRACT
THIS REPORT discusses methods for municipal dis-
posal of bulky metal objects. The use of compression
presses to reduce the volume of these objects was
investigated and found to be acceptable under certain
conditions. Capital investment estimates and evalua-
tion of operating costs for metal presses installed at
two separate locations are reported. The amount of
metal to be handled in the District of Columbia is
not sufficient to achieve a good economy of operation.
The alternate use of outside contractors or metal
shredding as a potentially more economical solution
is recommended.
INTRODUCTION
IN THE FIELD of municipal refuse collection and
disposal, a serious problem is presented by large
bulky metal objects which are both incombustible
and unsatisfactory for direct burial in sanitary landfills.
These objects consist largely of discarded refrigerators,
washing machines, stoves, water boilers, bed springs,
oil drums, etc. Where there is lack of interest by
local scrap dealers in the salvage of this material, it
may be disposed of in landfills. Good landfill opera-
tion, however, rules against disposal by this method
because the voids created can harbor rodents and
vermin. Also, decomposition of the metal by rusting
allows settlement of the reclaimed land to eventually
occur and the volume of scarce landfill space taken
up is excessive. Hence, reduction of the bulk becomes
desirable.
This report discusses the investigation of compres-
sion presses to accomplish size reduction of bulky
metal objects and presents recommendations regarding
the installation of such equipment in Washington,
D.C. Two installations of hydraulic press units were
investigated, located, respectively, at the transfer
station and the site of the proposed Incinerator No.
5. The smaller unit selected for the transfer station
because of space limitations is capable of handling
most household type appliances. The larger unit
selected for installation at the incinerator plant would
be capable of handling most bulky metal objects
anticipated for discard in a large city, including
automobiles where necessary.
SUMMARY AND RECOMMENDATIONS
The undesirable effects of burying bulky metal
objects in landfill operations in the District of Colum-
bia could be alleviated by the immediate installation
of a hydraulic compression press at the refuse transfer
station located at New Jersey Avenue and K Street SE.
This installation would cost approximately $147,000.
Operating expenses are estimated to be $11 per ton
of metal processed. No economic savings would be
obtained by this installation but an undesirable
condition would be eliminated.
We recommend as a more satisfactory solution, the
installation of a shredder at the site of the proposed
No. 5 Incinerator to handle both bulky metal objects
and oversize burnable waste. However, at least 3
years may elapse before this plant could be placed in
operation. The installation of a bulky metal press for
use during the intervening period is not economical.
We recommend that consideration be given to an
agreement with a local scrap yard owner to compress
with his equipment the bulky metal objects currently
being collected by the city. A temporary contract
based on the city delivering the material to the scrap
yard and hauling the bales to landfill could be advan-
tageous.
The installation of a large press at the proposed
incinerator plant for a capital investment of $255,000
is not recommended where suitable shredding equip-
ment is installed to handle both oversize burnable
waste and bulky metal objects.
47
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DAY & ZIMMERMANN
SOURCE AND QUANTITY OF BULKY METAL OBJECTS
Residents of the District of Columbia discard bulky
metal objects by placing them on the curbside in
accordance with schedules issued by the Division of
Sanitation. This refuse is collected by city trucks and
currently is being trucked to an open dump. About
6,700 items were collected during the 1965-66 fiscal
year, broken down as follows:
Units
Refrigerators 2, 300
Washing machines.
Stoves
Water boilers - . .
Bedsprings . .
Oil drums
Air conditioners . .
1,700
800
400
1,100
300
100
In addition, appliance dealers and private collectors
hauled an estimated equal quantity to the open dump.
Thus, it may be stated, that approximately 15,000
bulky metal objects must be disposed of annually. It
should be noted that oversize burnable waste such as
overstuffed furniture, mattresses, etc., are not included
in the above figures. The disposition of oversize burn-
able waste is discussed in the preceding section,
Si'Zf Deduction of Overside Burnable Waste.
DISPOSAL METHODS
Satisfactory disposal of bulky metal objects either
for scrap metal salvage or for burial in sanitary land-
fills requires a reduction in the volume of the material
collected.
The advent of new technological processes in the
manufacture of steel, most particularly the basic
oxygen furnace, has reduced the demand for scrap
iron and upgraded the quality of scrap steel suitable
for use as raw charge. This has lowered the value of
unprocessed scrap to the point where it is uneconomi-
cal in most cities for scrap dealers to resell the material
as collected. Up to the present time, Washington,
D.C., has been one of those cities where waste metal
cannot be advantageously disposed of by the muni-
cipality through scrap dealers to the steel industry.
Volume reduction of bulky metal objects may be
accomplished by two basic methods. The first con-
sists of shredding the objects to reduce them to an
accumulation of small pieces which will occuppy
considerably less volume than in their original con-
dition. The second method is to reduce the volume
by compressing the bulky material in a large mechan-
ical or hydraulic press. If the metal is to be sold to
scrap metal dealers, the first method would be pref-
erable because contaminants can be eliminated by
magnetic separation. Scrap metal of higher percentage
iron content and better melting characteristics is
produced. Compression of bulky metal objects pro-
duces a bale of crushed metal approximately 1/20 of
the size of the original objects. This bale contains
impurities such as insulation, aluminum, copper, etc.,
which are not desirable in scrap sold for melting.
Either method produces suitable material for burying
in sanitary landfills.
Machinery is commercially available for processing
scrap by either of these methods. This equipment is
necessarily in the class of heavy machinery with
moderate to large power demands. Shredders may also
be used to reduce bulky combustible wastes into
material suitable for charging directly to municipal
incinerators. For this reason, discussion of this type
of equipment is contained in the companion section,
Si%e Reduction of Overside Burnable Waste.
Although baling presses may be either of the
mechanical or hydraulic type, the latter has a much
wider application in this field because of the relative
ease with which high compression pressures may be
achieved. Professional scrap dealers have used hydrau-
lic balers for many years although many are now
switching to shredders.
COMPRESSION EQUIPMENT
The principal factor governing the selection of a
hydraulic press is the maximum size of bulky metal
objects to be handled. The charge opening has to be
big enough to admit the object and the cavity has
to be deep enough to permit the door of the press
to be closed.
The largest object likely to be encountered by a
municipal installation would be a supermarket
frozen food display case having overall dimensions
approximately 12' x 5' x 5' If the sizes of bulky
metal objects are limited to those of typical house-
hold appliances, a press with an opening 8' x 4'
should be adequate.
It should be noted that most large balers are built
to accommodate objects 30" deep and that household
type appliances rarely exceed this dimension. Com-
mercial operators usually resort to crushing when
an object is too large. This crushing is normally
done by dropping the objects on each other.
A truck-mounted crane with hydraulic boom and
orange peel grapple can be used to charge the baler.
This equipment may also be used to remove ejected
-------
special studies for incinerators
49
bales, unload incoming trucks, and load outgoing
trucks.
In many instances it is advantageous to use the
baler to compress loose miscellaneous scrap metal
such as panels, sheet metal, and scrap. This material
can be handled by a hydraulically operated charging
pan which would permit the operator to prepare a
new charge while the press is going through a
compression cycle. The addition of this feature
would depend on the required production rate for
the facility and the type of material to be handled.
The design of machines varies slightly between
manufacturers. They normally operate in a horizontal
plane with a top charge opening and a hydraulically
operated covet or door which can either slide across
or swing down over the cavity. Two hydraulically
operated platens within the press are then operated
to produce the finished bale. The first normally moves
the length of the press cavity to a position which
determines the width of the finished bale. The second
platen is then stroked at right angles to the first to
produce a finished bale approximately square in cross
section and equal in height to the depth of the
charge cavity. The finished bale is usually ejected
by further hydraulic action to a position alongside
of the unit where it can be picked up by a crane.
The pressure on the face of the final ram will range
from 1,000 to 1,800 pounds per square inch depending
on the design of the specific machine and its hydraulic
system. Larger presses sometimes use two hydraulic
cylinders per platen to obtain a better distribution of
forces.
The finished bale density is normally 100 to 150
pounds per cubic foot, depending on the amount of
voids in the scrap metal being compressed. The volume
reduction will usually be 20 to 1 when the press is
charged with the material similar to household
appliances.
A baling press of this type, when operated by
commercial scrap dealers, can generally handle 5 to
20 tons of metal per hour. However, the bulkier the
material, the lower the rate, since the time consumed
in charging constitutes a large percentage of the time
cycle. Also the size reduction ratio of 20 to 1 only
applies to the bulkier material.
It is feasible to install a scrap metal baler in the
open but a housing for the hydraulic and electrical
control systems is desirable. The press should be
located adjacent to its control equipment.
A representative list of hydraulic baling equipment
manufacturers has been included in appendix A.
PROPOSED EQUIPMENT INSTALLATIONS
The installation in the District of Columbia of
two hydraulic bale presses for compressing bulky
metal objects has been investigated. A program ar-
ranged to integrate with other solid waste disposal
facilities would be to install one at the existing
transfer station located on New Jersey Avenue and
K Street SE., and the other at the site of proposed
Incinerator No. 5, east of the Anacostia River.
Although one of the larger size presses could handle
the largest objects anticipated, it cannot be accom-
modated spacewise at the existing transfer station.
On the other hand, there will be no supporting facilities
available at the site of Incinerator No. 5 for 3 years.
Therefore, a smaller press installed immediately at
the transfer station to be followed later by a larger
press at the new incinerator could provide an immedi-
ate solution to the current disposal problem and addi-
tional flexibility after 3 years.
A proposed arrangement for a press at the transfer
station is shown in figure 8. A press with a charge
opening approximately 10 feet long by 4 feet 6 inches
wide by 30 inches deep can be installed in trailer stall
no. 4, with the hydraulic system and control console
located in the adjacent storage room. All normally
encountered household appliances could be accom-
modated by this press. Bulky material would be stored
on the operating (dumping) floor and charged to the
press by a mobile crane operating on the dumping
floor in truck stall no. 4. Necessary locker and toilet
facilities for the operating personnel are available at
the transfer station.
A larger unit, having a charge opening with di-
mensions of approximately 14 feet by 6 feet by 44
inches deep could be installed at the new incinerator
plantsite. A press of this size can handle bulky metal
objects ranging in size up to automobiles with engines
and transmissions removed. It may be installed as
part of the main building or at the corner of the pro-
posed incinerator plantsite with the hydraulic system
and controls housed in an independent structure as
shown in figure 9. Bulky metal waste would be stored
in an area adjacent to the structure, with landscaping
as necessary to screen the working area from public
view. Materials handling would be accomplished by
a mobile truck-mounted crane operating in the ad-
jacent yard. It is anticipated that the operating per-
sonnel would use the locker and toilet facilities of
the incinerator plant.
An advantage of integrating the press installation
with the incinerator proper would be the ability to
-------
5—DUMPING FLOOR
PARTIAL ELEVATION
z
Z
BALE DISCHARGE AREA
-CONCRETE APRON-
PLAN ARRANGEMENT
FIG. 8. Proposed arrangement for installation of a bulky metal press at transfer station.
-------
•PRESS COVER
STORAGE AREA FOR
BULKY METAL
OBJECTS
,„„_]
i
IP
iff
PUMP ROOM
AND
CONTROL HOUS
1 1
1 h
i i
J^ '
|
-»-
^
E
23' -8"
C
CHARGS
OPENING
tf H\
L
zS-f
BALE
DISCH.
APRON
^
II TON CRANE,
HYDRAULIC BOOM WITH
ORANGE PEEL GRAPPLE
PARTIAL ELEVATION
TYPICAL II TON CRANE
SAFE WORKING LOAD TABLE '
WORKING
RADIUS
(IN Ft)
5
10
15
20
25
30
35
40
45
46
360' CONTINUOUS ROTATION
WITHOUT
OUTRIGGERS
WHEELS IN
22,000
13,760
6^80
4,000
ZfOO
1,810
1,050
860
320
100
WITH
OUTRIGGERS
22POO
19^00
12,850
8700
5.930
4.380
3JOO
2,570
1,900
1,540
a
a.
s
n>
1
'VARIES WITH DESIGN OF UNIT, ADJUSTED
FOR WEIGHT OF ORANGE PEEL GRAPPLE
PLOT PLAN
FIG. 9. A compression press arrangement.
-------
DAY & ZIMMERMANN
use the same truck routing and scales as are used for
normal refuse handling. Even though the press would
be located adjacent to the refuse pit, it would not be
practical to use the bridge crane for charging the
press, but it could be possible to transfer out of the
pit bulky objects which might be inadvertently
dumped there when mixed with normal refuse. The
best operation would still require a separate mobile
truck-mounted crane for normal charging and bale
removal operations.
Four men would be required to handle the work at
each press unit, namely: a crane operator, a hydraulic
press operator, a truck driver, and a laborer. However,
this would not be a full-time task. The equipment
could be manned by workers with other work assign-
ments in the transfer station or incinerator plant.
The work would include loading the press, forming
the bales, and handling and transporting the bales
to the landfill. Maintenance could be handled by
contract with a local shop or by maintenance per-
sonnel employed at the transfer station and/or in-
cinerator plant.
ESTIMATED CAPITAL INVESTMENT COSTS
The estimated cost of installation of an intermediate
size press in the transfer station would be approxi-
mately $147,000 as developed in table 48.
TABLE 48
ESTIMATED CAPITAL COSTS FOR INSTALLATION OF MEDIUM-SIZE PRESS
Site preparation and alterations to existing building. .. .
Delivered cost of purchased equipment
Installation cost including electrical
Mobile crane with orange peel grapple
Installed cost of physical equipment
Engineering
Field inspection/construction management
Contingency
Escalation to December 1967
Total estimated project cost
Estimated
cost
$7,000
82,000
16,000
20,000
125,000
10,000
2,000
8,000
2,000
147,000
The above estimate provides for installing the
press on concrete piers in trailer stall no. 4 with the
hydraulic system and control station located in the
adjacent storeroom space on the operating floor level
as shown in figure 8.
The estimated cost of installation of a large size
press in a separate building at the incinerator plantsite
would be approximately $255,000, as developed in
table 49.
TABLE 49
ESTIMATED CAPITAL COSTS TOR INSTALLATION OF LARGE PRESS
Site preparation, foundation, and building
Delivered cost of purchased equipment
Installation cost including electrical
Mobile crane with orange peel grapple
Installed cost of physical equipment
Engineering
Field inspection/construction management
Contingency
Escalation to December 1969 .*.
Total estimated project cost
Estimated
cost
$34, 000
129, 000
18,000
31,000
212, 000
11,000
5,000
16,000
11,000
255, 000
The above estimate provides for the installation
of the large press at an independent location in the
immediate vicinity of Incinerator Plant No. 5 as
shown in figure 9- The estimate does not include the
furnishing of electric power to the site, toilet and
locker room facilities, or site development such as
access roads, grading, or landscaping. The estimate
does take into account the need for piling under the
heavy equipment due to anticipated poor soil condi-
tions. The building to house the hydraulic and control
equipment would be a brick and steel frame structure
erected above grade level. Electrical work included
in the estimate originates at a disconnect switch in
the control building.
ESTIMATED OPERATING COSTS
As indicated above, each press would require four
men to operate it. The following table indicates the
annual payroll costs for these four men, including
allowances for vacation, retirement, and overhead:
Job classification:
Crane operator
Truck driver
Press operator
Laborer
Gross labor cost
Annual
wages
$8,000
. 7,500
7,100
6,000
. 28,700
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special studies for incinerators
53
It has also been previously stated that each press
could handle from 5 to 20 tons of metal per hour.
Due to the extreme bulkiness of the scrap to be handled
it has been assumed that the lower figure would be
typical of the performance that could be exepcted
from each press. If the gross annual load to be handled
is in the order of 3,750 tons a year, only 15 tons per
operating day would require handling. Allowing
some time each day for starting up and cleaning up,
only 4 hours of operation of one press are required
to handle the entire load. If both presses are used,
only 2 hours per day on each would be required. Men
from the transfer station and/or the incinerator regu-
lar operations could be used part time to handle the
bulky metal objects. For this reason, operating labor
costs based on the hours actually expended will be
used in the operating cost estimate.
Included in the following tabulation of operating
costs are electric power and fuel costs and maintenance
costs prorated according to the hours of operation.
Fixed charges are based on the capital investment
being paid off over a 10-year period at an interest
rate of 4.5 percent per annum.
The table on the following page lists operating
costs for each press on the basis of 2 hours, 4 hours,
and 8 hours per day operation. If both presses were
used 2 hours per day to handle the anticipated load
of 15 tons per day, the cost would be $20 per ton.
However, if only the smaller press were installed and
it were operated 4 hours per day, the cost would drop
to $11 per ton.
APPENDIX B
Representative List of Manufacturers of Hydraulic Press
Equipment
D. and J. Press Co., Inc., North Tonawanda, N.Y.
Dempster Bros., Inc., Knoxville, Tenn.
Harris Press and Shear Co., Cordele, Ga.
Logemann Bros., Inc., Milwaukee, Wis.
TABLE 50
ANNUAL OPERATING COSTS
Tons of bulky metal objects per day
Tons of bulky metal objects per year
OPERATING COSTS
Maintenance
rocessmg cost per on
Transfer station press
2 hours
per day
7>'2
1,875
$147, 000
$7,200
$2,000
$2, 200
$11, 400
$18,600
$30, 000
$16
$120
4 hours
per day
15
3,750
$147, 000
$14, 350
$4,000
$4,400
$22, 750
$18, 600
$41, 350
$11
$165
8 hours
per day
30
7,500
$147, 000
$28, 700
$8,000
$8,800
$45,500
$18, 600
$64, 100
$9
$256
Incinerator No. 5 press
2 hours
per day
7/2
1,875
$255, 000
$7,200
$2,000
$3,800
$13, 000
$32, 400
$45,400
$24
$181
4 hours
per day
15
3,750
$255, 000
$14, 350
$4,000
$7,600
$25, 950
$32, 400
$58, 350
$16
$233
8 hours
per day
30
7,500
$255, 000
$28, 700
$8,000
$15, 200
$51,900
$32,400
$84, 300
$11
$337
Combined
operation
2 hours
per day
15
3,750
$402,000
$14, 400
$4,000
$6,000
$24, 400
$51, 000
$75,400
$20
$301
-------
heat recovery
ABSTRACT
SEVERAL apparently successful European applica-
tions of steam boilers to municipal refuse incinerators
have prompted consideration of similar installations
for American incinerators. American operating ex-
perience with incinerator heat recovery boilers has
been limited, and no outstanding pattern of successful
operation has been established.
In order to evaluate this disparity between Euro-
pean and American practice, this report compares the
typical refuse compositions, refuse heating values,
and the applications of heat recovery equipment to
incinerator furnaces.
Consideration is given to both refractory and water-
cooled furnaces, their effect on excess air require-
ments, and the economics of the sale of steam or other
methods of heat dissipation.
For the proposed Washington, D.C., Incinerator
No. 5, the report reviews the application of a boiler
plant capable of burning 800 tons of refuse per day
with four incinerator furnaces. The economics of the
proposed plant do not justify the installation of heat
recovery equipment.
INTRODUCTION
THERE HAS BEEN considerable discussion recently
regarding the application of heat recovery equipment
to municipal refuse incinerators. Many industrial
publications list accounts of refuse incinerator boiler
units installed in European cities where the avail-
able heat energy of municipal refuse is recovered and
used for the generation of steam. In contrast there
are relatively few such units installed in the United
States.
There is a considerable difference of opinion in the
United States as to the justification for installation
of boiler units on municipal waste incinerators. This
study has been conducted to determine what factors
should influence the decision to install heat recovery
equipment and what performance and maintenance
conditions can be anticipated.
Our analysis included studies of the following items
to determine their effect on performance and operating
costs: Refuse composition, ultimate analysis, and
heating value; relative characteristics of refractory
and water cooled furnaces; specific design require-
ments of boiler convection surfaces suitable for use
with incinerator furnace gases; the effect of heat
recovery equipment on flue gas volume due to a re-
duction in excess air requirements and a reduction
by convection cooling as compared to spray water
cooling; the effect of steam demand requirements on
incinerator operation; and, the effect of variations in
refuse moisture and furnace excess air on steam pro-
duction rates.
All of the above factors were applied to the opera-
tion of representative types of incinerator boiler units.
Four basic configurations of furnace, boiler, and exit
gas cooling were separately evaluated.
SUMMARY AND RECOMMENDATIONS
The composition of refuse reported in literature as
fired in European plants is characteristically lower in
combustible material and heating value than Ameri-
can refuse. U.S. refuse shows a reasonable amount
of uniformity in composition between equivalent
metropolitan areas.
The higher percentage of paper and plastic products
in American refuse is believed to explain a significant
additional carryover of ash and potentially corrosive
materials which are deposited on boiler tube surfaces.
Both European and U.S. experience indicates that
boiler tube damage has resulted from these deposits.
Modern refuse also contains products which are
known to burn to corrosive gases. The presence in the
refuse of large quantities of ash, as in Europe, provides
a material which can absorb and neutralize some of
these corrosive products.
Modifications to standard boiler designs will help
to reduce the accumulations of incinerator furnace
ash on the boiler tubes. These modifications, combined
with improved cleaning procedures and protection of
55
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DAY & ZIMMERMANN
boiler surfaces against dew-point condensation, should
reduce loss of tube metal.
Most refractory incinerator furnaces are operated at
excess air levels of 150 percent or greater. Waterwall
furnaces in Europe are reported to operate at excess
air levels as low as 50 percent but there is reasonable
doubt these lower levels are obtained without firing
of auxiliary fuels such as oil or pulverized coal. There
is no operating experience with waterwall furnaces
in the United States to evaluate the potential of
operation at lower excess air levels with municipal
refuse.
The generation of steam in a municipal refuse
incinerator plant cannot be reasonably varied to meet
seasonal load conditions, unless the plant is provided
with boiler bypass flues or steam condensing equip-
ment. Economical operation usually requires that the
plant be part of a large steam generating system.
Plant auxiliaries are affected by the type of instal-
lation and operation selected. These include storage
pit capacity, air pollution control equipment, and
fan sizes. Steam generating capacity -is influenced by
the type of furnace, the amount of excess air, and
the moisture content of the refuse. Auxiliary fuel
firing is recommended where steam is sold or a mini-
mum steam production is required.
A cost comparison of four different incinerator and
incinerator boiler arrangements indicates that the
lowest annual operating expense is usually antici-
pated with a conventional refractory furnace design.
Plants incorporating steam boilers can be operated at
lower annual expenses than a conventional incinera-
tor plant only if a firm market can be obtained for
all of the steam production at rates high enough to
cover the additional operating expenses. A water-
wall furnace designed to permit operation at low
excess air levels costs slightly more to install and
operate than a refractory wall furnace.
The installation of water-cooled furnaces or steam
boilers in the proposed No. 5 Incinerator plant is
not recommended for the following reasons: (1) The
anticipated operating expense of water-cooled furnace
installations is higher than the refractory furnace
type. (2) The trend of refuse composition toward
additional plastics, freons, etc., will probably in-
crease the existing critical metallic tube maintenance
from corrosive products of combustion with insuffi-
cient assurance that present technology can deliver
a boiler design that will be satisfactory for the pres-
ent trends of refuse composition. (3) Reductions in
operating economies, capital costs, etc., resulting
from the lower gas velocities potentially available
with lower excess air operation are not sufficiently
assured to warrant consideration of water-cooled
furnaces without an employable market for the re-
covered heat. (4) There is no apparent market for
the sale of steam produced in this plant. (5) Successful
operation at the lower excess air levels recommended
for water-cooled furnace installations has not been
proven.
REFUSE COMPOSITION
The composition of refuse burned in a municipal
incinerator can vary to some degree with the economic
living standards in the area, with the seasons of the
year, and with the specific weather conditions on the
particular day the refuse is collected. Reference to
published data on refuse composition must be made
with caution as the methods of sampling, analysis,
and reporting vary between individual reports.
Three refuse analyses, each using two different
methods of expressing the bulk composition of refuse,
have been tabulated (table 51). The analysis of the
Washington refuse has been assembled from data
published in the Division of Sanitation Annual Report
of Collection and Disposal for the fiscal years 1965 and
1966 and from supplementary discussions with the
Sanitation Division. The analyses of a typical refuse
composition for an American municipality is based
on a report by Kaiser (2). The analysis of a typical
European municipal winter refuse is based on work
by Eberhardt (2, 3).
As indicated by a comparison of the analyses in
table 51, European refuse contained a higher percent-
age by weight of garbage, water, ash and noncom-
bustible trash than American refuse. This was ap-
parently due to a lower percentage of paper and wood
products in European refuse.
The higher moisture and ash content of European
refuse significantly lowers the heating value and
reflected a need for auxiliary fuel burners to maintain
ignition.
Kaiser in his work on chemical analyses of refuse
components presented data on the "proximate" and
ultimate analyses of 20 components of municipal
refuse (1). This author also reported a breakdown of
the probable constituents of this refuse on a percentage
basis by weight of the total refuse.
This data was applied to available information on
Washington refuse and the following ultimate analy-
sis for the refuse composite was developed.
-------
special studies for incinerators
57
Percent
Carbon 27.6
Hydrogen 3.8
Oxygen 24.5
Nitrogen .3
Sulfur 1
Water 20.0
Ash 23.7
Total 100.0
This ultimate analysis on a 20 percent moisture
basis results in a heating value of 5,069 Btu per
pound of refuse.
This analysis and heating value was used for the
calculation of combustion air requirements, flue gas
analyses, furnace temperatures, heat transfer, and
steam generating capabilities of the furnace configura-
tions included in this study.
The procedure used to determine the above ultimate
analysis can be followed wherever a reasonable esti-
mate of the composition by components of the refuse
is available. Application of the weighted percentages
of the refuse components to the ultimate analyses
reported by Kaiser (7.) will produce an equivalent
ultimate analysis.
The analysis prepared for the previous section,
entitled, Study of Municipal Incinerator Effluent
Gases, was modified to forecast the future proba-
bility of additional plastics in the refuse and there-
fore shows a slightly different ultimate analysis.
Appendix C presents an analysis of a typical muni-
cipal refuse patterned after the report by Kaiser (7.).
Included in this table are the ultimate analyses of
components useful in the development of a composite
analysis.
EFFECT OF INCINERATOR OPERATION
ON BOILER PERFORMANCE AND DESIGN
Products from the combustion of incinerator refuse
are known to affect boiler operation and maintenance
both in the United States and Europe. These products
include clay fillers of papers and plastics; salts of
sodium, potassium and calcium; silicates, acids from
the combustion of freons (pressurized cans), unburned
hydrocarbons (soot), and water vapor.
Local zones of combustion of dry refuse with zero
excess air permit theoretical refuse bed temperatures
in excess of 3,700° F. Actual temperatures attained
are sufficient to volatize a significant quantity of
material. Fuel bed and furnace gas velocities are
generally sufficient to convey the volatilized material
and the low density particles to and beyond the furnace
exit. Any obstructing surface, such as a convection
boiler tube, can receive this material by impingement.
If the material is plastic or adhesive, the deposit will
TABLE 51
TYPICAL REFUSE ANALYSES
Refuse composition :
Garbage
Refuse analysis :
Ash
Heating values :
Refuse at 20 percent moisture
percent . .
do
- do
do
do
do
B t u /lb
do
do
do
Washington,
D.C.
11.2
78 0
10 8
11 0
26 4
62 6
5 639
6, 336
10 121
5 069
American
municipality '
12.4
81 7
5 9
11 7
22 3
66 0
5 955
6 744
9 023
5 395
European
municipality 2
23.0
61 5
15 5
23 7
41 0
35 3
^ 649
4 773
10 317
3 818
1 The analysis of a typical refuse composition for an American municipality is based on the report by
Kaiser 0).
,2 The analysis of a typical European municipal winter refuse is based on information in references 2 and 3.
3 Moisture content varies as noted above.
4 Moisture and ash free.
-------
DAY & ZIMMERMANN
accumulate. If the material is nonadhesive, erosion
may occur when bare metal is exposed to nonadhering
abrasive material. The rate of erosion will depend on
the velocity of impingement.
Practicallv all of the flue-mounted convection boiler
installations on incinerators in this country suffer from
troublesome accumulations of deposits on the boiler
tubes. In many of these installations the deposits
become corrosive. During the initial stage of the
deposit accumulation, the boiler steaming capacity is
reduced by the insulating effect of the deposit and the
boiler exit gas temperature increases. If the deposit
is allowed to accumulate, the gas passages become
plugged and eventually limit the available draft
required to pass the gaseous products of combustion.
To avoid "positive furnace draft" or back pressure
in the furnace, the undergrate airflow is then reduced,
usually without reducing the refuse feeding rate. The
resultant lower furnace excess air develops higher
furnace and refuse bed temperatures which, in turn,
develop excessive furnace slagging, clinkering, ash
pit combustible loss, stack smoke, and greater furnace
and stoker maintenance.
Boiler tube deposits from municipal waste inciner-
ators are generally so cementations that retractable
soot blowers, where employed, are not adequate.
Additional frequent manual cleaning during boiler
shutdowns is usually required to maintain capacity
operations.
Most of the existing incinerator boiler installations
in the United States have been made using conven-
tional designs of steam boilers, with relatively close
tube spacing to obtain maximum steaming capacity
and efficiency at minimum cost. The opportunity to
accumulate deposits would be reduced if the tube
spacing were increased by several inches. This change
would also enable more effective cleaning.
This increased tube spacing should reduce loss of
boiler capacity and availability but will significantly
increase boiler costs and reduce the steaming capacity
and efficiency. A design allowance for a 640° F boiler
exit gas temperature should obtain a useful installation
without excessive additional cost.
The overall operating experience at several East Coast
installations (appendix D) indicates that the boiler
inlet gas temperature should be below 2,000° F
(1,800° F maximum appears tolerable) and that the
flame travel pattern should be long enough to avoid
impingement on the convection tubes. This should
permit solidifkarion of enough of the molten or ad-
hesive particles to adequately reduce the slagging or
deposit accumulating rate to within the range con-
trollable by the boiler tube spacing design. If lower
furnace exit temperatures are obtained with additional
furnace excess air, the increased gas velocity increases
the furnace particulate emission rate, the boiler draft
loss, and the required forced and induced draft fan
capacities. All of these conditions will increase the
rate of any erosion and the rate of deposit accumula-
tions.
The alternative to lowering furnace exit tempera-
tures by additional furnace air, is the addition of
furnace wall cooling. Radiant heat absorption by the
furnace walls can reduce the furnace temperatures so
as to enable operation at significantly lower excess
air levels. This in turn will reduce the furnace par-
ticulate emission rate, the boiler draft loss, and the
required fan capacities. All of these conditions asso-
ciated with a water-cooled furnace should reduce the
rate of convection boiler tube erosion and deposit
accumulations.
Water-cooled furnaces have been in service for
several years in European incinerators, with refuse
conditions and operating levels different from those
employed in the United States. Several American in-
stallations using water-cooled furnaces are currently
being considered and one is about ready for initial
service (4). It should be noted that no satisfactory
operating experience record has been developed on
this type of plant in the United States. The experience
reported from the limited operations of the water-
cooled nonsteam generating furnace installations at
Framingham, Mass., and Whitemarsh Township, Pa.,
is not useful for evaluating the steam generating heat
recovery type of operations being considered in this
report.
The available design information for water-cooled
furnace installations indicates that a minimum tube
temperature of 400° F is required to avoid external
tube corrosion, and that auxiliary fuel burners will
probably be required to maintain ignition of wet or
low heating value refuse. Tube corrosion of a more
complex nature is also known to occur at metal
temperatures above 750° F (2, 3). The chlorides and
fluorides from the combustion of polyvinylchloride
plastics and from the incineration of freons in pres-
surized cans can cause extensive damage to metal
surfaces in the incinerator.
In addition to the direct action from the products
of combustion, a severe dew-point corrosion potential
exists in incinerator furnaces. The total moisture
content of the gaseous products of combustion result-
-------
special studies for incinerators
59
ing from the combined effects of the moisture content
of the refuse, the moisture produced by the combus-
tion of hydrogen in the fuel, and the moisture in
the combustion air creates a dew-point condition
which may react with the products of' combustion
to develop corrosion on any exposed metallic surfaces
at temperatures of less than 400° F (4, 5). Although
there may be few such critical spots during normal
operation, all boiler tube surfaces may be exposed
to dew-point condensation and corrosion during low
burning periods and boiler startup or shutdown
operations. The hygroscopic nature of some boiler
tube deposits tends to aggravate this condition
during boiler shutdowns.
To minimize this dewpoint corrosion, the tube
metal temperatures need to be held above the gas
dewpoint with auxiliary furnace heat or with steam
circulation during low temperature operating condi-
tions, or the hours of such exposure must be held
to a minimum. This preventive maintenance is not
generally practiced in American incinerator boiler
plants.
EFFECT OF BOILER OPERATION ON INCINERATOR
PERFORMANCE AND DESIGN
Li order to evaluate the feasibility of the equipment
arrangements available to designers of incinerator
boiler plants, it is necessary to consider the effect
of the boiler on the overall operation of the plant.
The primary purpose of an incinerator plant is the
reduction in volume and combustible content of the
refuse to permit maximum utilization of landfill space
for the disposal of the ash residue. The incineration
process must be conducted in a manner which will
minimize pollution of the atmosphere and limit
pollution of the ground and water sources from
contact with the ash residue.
These conditions cannot be obtained without
adequate incineration of the combustible content of
the refuse in a furnace atmosphere that provides the
necessary temperature to insure acceptable burnout
of the residue and the gaseous products of combustion.
Typical incinerator operating practice in the United
States is maintained with excess combustion air of 150
to 200 percent in refractory furnaces to obtain satis-
factory burnout of the refuse and acceptable furnace
temperatures. The use of a water-cooled furnace
requires a reduction in excess air to approximately
50 percent to maintain the necessary furnace ignition
and exit temperatures. The effect of this reduction in
excess air on the burnout of the refuse and flue gases
has not been determined in plants burning U.S. refuse.
The excess air quantities for incinerator operation in
European plants are reported (2, 3) to be 50 to 70
percent -with water-cooled furnaces having widely
amounts of supplementary firing of fuel oil and pul-
verized coal. No definite trend of excess air require-
ments has been obtained from published data on
European operations.
A few attempts have been made in the United States
to operate continuous feed incinerator grates in
refractory furnaces at low excess air levels; these re-
sulted in heavy slag accumulations on the furnace
sidewalls and refuse clinkering. It has been reported
().
This lack of encouraging experience with lower excess
air operation—and the indication that satisfactory
burnout of American refuse is obtainable only with
undergrate excess air levels above 100 percent and
furnace outlet excess air levels above 150 percent—
practically specifies a minimum 150 percent excess air
design for any new incinerator application.
The primary purpose of most steam generating plants
is to produce a quantity of steam that varies with the
demand. Seasonal loads for heating and air condition-
ing, combined with daily and weekly variations in
process steam loads, create varying load conditions
which are readily compensated for in a normal fuel
fired installation by a variation in the fuel firing rate.
In contrast, the steam production capability from an
incinerator boiler will vary with the instantaneous
available heat from the burning refuse. Steam produc-
tion charts from refuse fired incinerator boilers show
rather wide variations in the quantity of steam gen-
erated when the unit is operated with a steady refuse
feeder speed and fixed airflow dampers. See the section
of this report, Factors Affecting Steam Generating
Capacity. For a controlled boiler steam output,
auxiliary fuel firing is required to compensate for the
varying usable heat from refuse in the furnace. The
average daily steam production, either with or without
auxiliary fuel firing, umst correspond to the rate at
which refuse must be incinerated. It is impractical to
store large quantities of refuse for several weeks or
months to meet winter peak steam demands.
The installation of an incinerator refuse boiler as
the only source of steam to be sold at commercial rates
-------
DAY & ZIMMERMANN
must provide for auxiliary firing to meet maximum
steam demands if wet refuse or lack of refuse begins
to limit production. In addition, the plant must be
provided with steam condensing facilities or boiler
bypass flues to handle excess steam production capa-
bility when steam loads are limited.
The most practical installation of an incinerator
boiler unit is as part of a large system where the mini-
mum steam demand is greater than the capacity of
the incinerator boiler units. Under this condition
the momentary variations of steam output will not
upset system pressures. Also, minimum steam demands
will not require wasting of the steam production from
the incinerator boilers. It is interesting to note that
most of the European incinerator boiler plants re-
ported in literature supplement steam from other
sources in this manner.
The design of refuse storage facilities and selection
of incinerator furnace sizes must consider the needs of
the steam generating equipment. A plant designed to
receive an average of 800 tons per weekday of mu-
nicipal refuse would receive 4,000 tons of rufuse per
week of 5-day refuse collections. Burning this mate-
rial over 7 days would require an incinerator-boiler
total capacity of approximately 575 tons per day. This
would represent three incinerator-boiler units of
approximately 200-tons-per-day capacity each. A
fourth unit would be required as standby to permit
the plant to meet steam demand requirements if one
unit is out of service. This results in a total installed
capacity of 800 tons per day even though the plant is
operating 7 days a week.
The storage pit of an incinerator boiler plant must
be capable of holding sufficient refuse to maintain
operations at rated loads from the end of refuse de-
liveries on Friday afternoons (approximately 4 p.m.)
to the beginning of refuse deliveries on Monday morn-
ing (approximately 9 a.m.). This represents approxi-
mately 65 hours of refuse storage. On the other hand,
the storage pit of a plant designed for 5-day, 24-hour
operation must be capable of holding sufficient refuse
to maintain operations at rated loads fdr approxi-
mately 17 hours. Conversion of these hours of opera-
tion to tonnage figures indicates a refuse storage bin
requirement approximately 2.7 times larger for the
incinerator boiler plant, operating 7 days per week as
compared to an incinerator plant operating 5 days
per week. This has a significant effect on the capital
investment requirements.
Manpower requirements of an incinerator boiler
plant are normally greater than an incinerator plant.
In most States, licensed boiler operators are required
because of the operation of fired pressure vessels. In
addition, the plant will require additional personnel
to operate and maintain necessary water treating
equipment, steam condensing equipment, boiler feed
pumps, auxiliary firing equipment, a deaerating heater,
condensate pumps, etc. This represents a substantial
increase in operating labor over the normal incinera-
tor operation. The plant is also committed to a more
rigid schedule with 7 days per week, 24 hours per day,
utility type operation. This is more demanding on
the plant management and personnel.
FACTORS AFFECTING STEAM GENERATING CAPACITY
The steam generating capability of an incinerator
boiler combination is noticeably affected by both
moisture in the fuel and the excess air used to burn
the refuse.
The moisture in the fuel is beyond the control of
the plant operator as it is determined by the manner
in which the refuse is discarded, protected from the
weather (rain and drying winds), and collected.
Additional moisture is occasionally added by the
plant operators in the storage bins to control dust.
Momentary variations in the refuse are determined
by the amount of garbage, grass clippings, etc.,
present as the refuse is burned. Figure 10 shows the
variations in steam generating capacity with moisture
content of the refuse for two furnace conditions.
An increase in moisture content from 10 to 20 per-
cent can reduce the steam generating capacity 26
percent (from 1.9 to 1.6 Ibs. of steam per pound of
refuse) in a refractory furnace with a flue-mounted
boiler operating at 200 percent excess air. The corre-
sponding change in a water-cooled furnace installa-
tion operating at 60 percent excess air is an 18-percent
decrease (from 3-3 to 2.8 Ibs of steam per Ib of
refuse) (fig. 10).
Coupled with the changes due to mositure content
are changes due to excess air variations. With con-
ventional incinerator operation, the furnace draft is
maintained constant. The airflow through the refuse
bed is the resultant of the average back pressure
developed by the depth, density, and porosity of the
lefuse and the volume-pressure characteristics of the
forced draft fan. The variations in the total under-
grate airflow can be either gradual or sudden and
usually frequent because of the varying refuse bed
conditions.
The actual refuse feeding rate in pounds per minute
varies widely because of varying refuse density, even
-------
special studies for incinerators
61
ER WALL UNIT
EXCESS AIR
U)
U_
O
LO
Q
O
CL
1.0-
0.5-
REFRACTORY FURNACE
AT2007«EXCESS AIR
10
20
40
PERCENT OF MOISTURE IN REFUSE
FIG. 10. Effect of refuse moisture on steam generating capacity.
though the cubic feet per minute may be constant.
This variation in feeding rate, combined with wide
variations in the heating value of the material being
charged (such as changes from wet garbage to free
burning plastics), can cause considerable variation in
the steam generating rate.
The undergrate combustion excess air that results
from the varying airflow and combustible content of
the refuse varies haphazardly and frequently over a
range of 10 to 50 percent of the excess air from the
average condition.
An increase in excess air of 50 percent (from 150
to 200 percent) in a refractory furnace flue-mounted
boiler can reduce the steam generated per pound of
refuse by 11 percent (from 1.8 to 1.6); the correspond-
ing change in a water-cooled furnace unit for an
-------
62
DAY & ZIMMERMANN
increase of 50 percent excess air (from 50 to 100
percent) is 7 percent (from 2.8 to 2.6) (fig. 11).
As a result of variations in moisture, excess air,
combustible feeding rate, and heating value of the
combustible in the refuse, the steam generating
capacity of an incinerator-fired boiler without auxil-
iary firing can haphazardly vary from approximately
zero to 3-5 pounds of steam per pound of refuse fed.
If a constant steaming capacity is required from
the plant, auxiliary fuel burners with adequate
capacity, instantly available, are required.
EFFECT OF BOILER INSTALLATION
ON Am POLLUTION CONTROL EQUIPMENT
The proper size of air pollution control equipment
is determined by both the method of operation of
the furnace (excess air) and the method of gas cooling
UJ
tO
LJ
CH
Li_
O
O
o
CL
cr
LJ
CL
2.5
2.0
1.5-
LU
I—
tO
U_
O
to i.o
Q
O
CL
0.5-
50 100 150 200
PERCENT EXCESS AIR AT BOILER OUTLET
250
300
FIG. 11. Effect of excess air on steam generating capacity.
-------
special studies for incinerators
63
(boiler, spray water cooling, or cooling by air dilu-
tion). Evaluation of capital and operating costs
requires that these factors be considered in the
selection of the equipment.
The excess air requirements used for design of
water-cooled and refractory wall furnaces are selected
to obtain a furnace exit temperature below 1,800°
F for entry into the boiler convection surfaces. We
have calculated the volume of the products of com-
bustion of a water-cooled furnace designed to operate
at 60 percent excess air and a refractory walled
furnace designed to operate at 200 percent excess
air. These curves are appropriate only for a specific
design and will vary with the heat absorption of
the refractory or waterwall furnace enclosures. The
changes in volume due to additional cooling of these
gases by various methods is shown graphically in
figure 12. The exit gas volume of the water-cooled
furnace will be approximately 120,000 c.f.m. as
compared to 165,000 c.f.m. leaving the refractory
furnace. This difference is due to the different amounts
of excess air used in the two furnaces.
The gases leaving the furnaces can then be addi-
tionally cooled by passing them through a boiler.
The resulting boiler exit volumes are 60,000 c.f.m.
and 105,000 c.f.m., respectively, at a temperature of
approximately 640° F.
If the furnace gases are discharged through a boiler
bypass with spray cooling to reduce the temperatures,
then the final gas volumes will be greater than those
of the gases cooled by a boiler. These volumes will
be approximately 125,000 c.f.m. and 82,000 c.f.m.,
respectively, at a temperature of 640° F.
The capacity of the dust collector for this partic-
ular application may vary between 60,000 and 125,000
c.f.m., depending upon the details of the incinerator
boiler installation.
The use of dilution air for cooling produces an ex-
cessive volume of flue gas (as shown in fig. 12 by
the broken line). The corresponding dust collector
capacity tor a refractory furnace installation using air
dilution cooling would be approximately 260,000
c.f.m., requiring a dust collector four times the size
of the unit for a waterwall. furnace and boiler
combination.
DESCRIPTION OF EQUIPMENT ARRANGEMENTS
We have included in this study four basic configura-
tions of incinerator furnaces and boilers. These have
been selected to cover the major variations of incin-
erator boiler combinations. These four are briefly
described as follows: Case I: Conventional refrac-
tory furnace with spray cooling of flue gas; Case II:
conventional refractory furnace with spray cooling
of flue gas and boiler in by-pass flue; Case III: water-
wall furnace with convection boiler; and, Case IV:
waterwall furnace with spray cooling of flue gas.
Each case was studied to determine operating char-
acteristics, steam production capability, and annual
owning and operating costs.
Included in the capital cost estimates for each of
the arrangements are all items of equipment and struc-
ture which are considered to vary between any of
the arrangements. All equipment is considered to be
fully enclosed within structures of comparable unit
cost, with the size of the structure varied to suit the
space requirements of the equipment. Adjustments in
cost were made for pit capacity required for 7-day
operational steam-producing plants to permit storage
of refuse adequate for continuous operation from
Friday afternoon to Monday morning. The sizing and
cost of auxiliary equipment such as cyclone dust
collectors, electrostatic precipitators, and fans has
been adjusted for the gas volume resulting from opera-
tion of the specific type of unit. These and other
considerations are discussed in the following case
descriptions:
CASE I
The Conventional Refractory Furnace with Spray Cooling
of Flue Gas.—This furnace type is included in this study
as the base for comparison with steam producing and
water-cooled furnace designs. It is shown schemati-
cally in figure 13. It has been assumed that this plant
will contain four, 250-ton-per-day incinerator units,
with a maximum installed capacity of 1,000 tons per
day. Our study is based upon normal operation of
the four units at 80 percent of load for a total plant
capacity of 800 tons per day for 5 days, equivalent to
4,000 tons per week. Overcapacity of the units has
been provided to permit the plant to process 750 tons
per day with one unit out of service.
The pit storage capacity has been selected to
correspond 'with the anticipated 800-ton-per-day oper-
ation. Manpower requirements are based upon a
three-shift, 5-day-per-week operation.
It is anticipated that operation of this plant would
be maintained with 150 percent excess airflow through
the grates and additional overfire air to bring the
furnace exit gas to a condition of approximately 200
percent excess air or 6 percent CO2.
-------
64
DAY & ZIMMERMANN
300-
CC
LU
Q_
t—
LU
LU
U_
O
CD
Z3
U
Q
ID
o
:r
250-
EOO-
150-
50-
X
X
X
GAS VOLUME LEAVING
— REFRACTORY FURNACE
AT ZOO/.EXCESS Al R X
X
X
GAS VOLUME LEAVING WATER
-COOLED FURNACE AT 60 70
EXCESS AlR
1750
1500
1000
750
500
FLUE GAS TEMPERATURE-DEGREES FAHRENHEIT
LEGEND
VOLUME CHANGE BY
COOLING WITH BOILER
VOLUME CHANGE BY
SPRAY COOLING W/WATER
VOLUME CHANGE USING
Al R DILLUTION COOLING
FIG. 12. Changes in flue gas volumes as determined by gas cooling methods.
-------
special studies -for incinerators
APPROX. 255'-0"
65
A
I 3°
i o
_r
PLAN OF 4 UNITS
ELECTROSTATIC
MECHANICAL PRECIPITATOR
CYCLONE J| I |_
COLLECTOR
TYPICAL ELEVATION THRU SINGLE UNIT
FIG. 13. Case I. Schematic arrangement of the conventional refractory furnace with spray cooling of flue gas.
The furnace has been selected for an average heat
release of 15,000 B.t.u. per cubic foot of furnace
volume. Maximum furnace temperature in the zone
of active burning is calculated to be approximately
2,250° F. The gases would be at a temperature of
1,260° F. when they leave the furnace to enter the
spray chamber. The exit gases from the furnace
would be cooled with water sprays to a temperature
of 550° F. entering the air pollution control equip-
ment. This temperature is selected to permit the use
of smaller sizes of air pollution control equipment.
Electric power and water consumption for this case
are based upon these conditions.
CASE II
The Conventional Refractory Furnace with S~pray Cooling
of Flue Gas and Boiler in Bypass Flue.—This case covers
the addition of a flue-mounted, convection type, heat
recovery boiler to case I and is shown schematically
in figure 14. This unit would be equivalent in furnace
size and operating conditions to the unit specified
in case I, except that the flue gas would normally be
cooled to approximately 640° F. by the boiler as
indicated by the curves in figure 12. It has been as-
sumed that this plant would sell steam; therefore,
pit storage capacity and manpower requirements are
based on a 7-day-per-week, 24-hour-per-day operation.
-------
DAY Sc ZIMMERMANN
APPROX. 255';0"
n—r
PLAN OF 4 UNITS
ELECTROSTATIC
MECHANICAL PRECIP1TATOR
CYCLONE I I | [_
COLLECTOR
vw
REFRACTORY
DAMPERS
FIG. l4.CaseII.Sch,
TYPICAL ELEVATION THRU SINGLE UNIT
of the conventional refractory furnace with spray cooling of flue gas andboiler in bypass flue.
Water treating and pumping equipment has been
included to provide for 100 percent makeup of the
water used for boiler feed requirements. The plant is
provided with a bypass flue with spray cooling of the
gases to permit continuous operation for burning
refuse if the steam load fluctuates to meet daily and
seasonal loads. Auxiliary oil burning equipment has
been added to the refuse furnace to smooth out steam
production rates (maintain constant boiler pressure)
and to maintain steam production at the design capac-
itv •when moisture content of the refuse increases.
The furnace conditions would be identical to case
I. The gases leaving the boiler would be of less volume
and weight than the gases leaving the spray chamber
of case I; however, because of the boiler bypass flue,
it has been necessary to size the air pollution control
equipment for the weight and volume of gas that
would leave the spray cooled flue.
CASE III
The Waterwall Furnace with Convection Boiler.—This
furnace is based upon the use of a water-cooled fui-
-------
r-
special studies for incinerators
APPROX. 225-0
67
s yr- --- t \
^-i k :
~i
-t-
OJ
o.
o
~D
"D
L'\.TS
•I.
STACK
ELECTROS TAT
-REC'PTATCr
\MECKAMCAL l~| M
icir: >INF J I—11
INDUCED/
DSAF' '
FAN' •
i O'
\
\
—
! JAAT£.; AA.._
i -.K\ACE
1 1
!
{COLLECTOR
\ On
\ — i
^ECO \OV ;~c ^ !
—-BO'LE^ V '
^\
U ^-v-^
\ ! I
^_j' J 1
.,-' i — J i
\ \ ,
L V
>,
T'iP.CAL ELE\"AT:0\ THRl: S KO_
FIG. 15- C.is< III. Scktrnjfic jrrjngtrntnt of icjter wjll furnace with conviction boihr.
nace with an integral con vend on boiler, similar in
arrangement to a conventional coal stoker-fired boiler
as used for steam production in industrial applications.
The anangement is shown schematically in figure 15.
Certain modifications to adapt this design of boiler
for incinerator refuse firing are included, such as
additional soot blowers of the retractable type and
wider tube spacing on die convection passes.
It has been assumed that this plant would sell
steam; therefore, pit storage capacity and manpower
requirements are based upon a 7-day-per-week opera-
tion. Water treating equipment has been included to
provide for 100 percent makeup of the water used for
boiler feed requirements.
The design of this type of unit will not permit the
inclusion of a boiler bypass flue. It has therefore been
-------
6S
ZIMMERMANN
necessary to include in the capital cost a 100 percent
capacity steam condensing installation to permit
constant burning of the refuse when steam demands are
low. Auxiliary oil burning equipment has been added
in the furnace to smooth out steam production rates
(maintain constant boiler pressure) and to maintain
steam production at the design capacity when mois-
ture content of the refuse increases.
Furnace conditions •would be different from those
selected for case I and case II. The manufacturers of
boiler equipment for this type of installation suggest
operation at relatively low excess air rates. Our cal-
culations are based upon 50 percent excess airflow
through the grates and additional overfire air to
bring the furnace exit gas to a condition of approxi-
mately 60 percent excess air or 12 percent CC>2.
The furnace has been selected for an average heat
release of 19,000 B.t.u. per cubic foot of furnace vol-
ume. Maximum furnace temperature in the zone of
active burning is calculated to be approximately
2,100° F. with the gases cooled to approximately
1,720° F. by the time they enter the convection sur-
faces of the boiler. The convection boiler would
further cool the gases to approximately 640° F. before
they enter the air pollution control equipment.
Electric power requirements for this case are less
because of the reduced weight of flue gas resulting
from operation at 60 percent excess air. Also the sizes
of the air pollution control equipment and fans are
significantly reduced over case I and case II equip-
ment sizes.
CASE IV
The. WaterwaII Furnace with Spray Cooling of the Flue
Gas.—This type has been selected to include in our
studies a water-cooled furnace as a replacement for a
refractory furnace, as shown schematicallyin figure 16.
This plant would be operated on a 5-day-per-week
basis with no intent to produce steam for sale. This
method of operation would permit the use of a smaller
refuse storage pit. It would lower manpower require-
ments, reduce the use of auxiliary oil, except as
necessary to maintain ignition in the water-cooled
furnace, and reduce makeup water and manpower
requirements.
This method eliminates the convection boiler from
case III and substitutes a forced circulation water-
cooled furnace with provision for spray cooling of
the flue gases. The savings in capital cost over case
III, resulting from the reduction in size of the refuse
storage pit and the elimination of the boiler convection
surfaces, are offset by capital expenditures for a spray
cooling chamber and larger dust collecting equipment.
ESTIMATED CAPITAL AND ANNUAL OPERATING COSTS
We have tabulated in table 52 the estimated incre-
mental capital costs and annual operating costs for
the cases described above. The capital costs include
only those items that vary from one type of installa-
tion to another and do not represent total capital
investment for a specific plant. The costs include
contractors' overhead and profit, engineering, field
supervision, and contingencies.
Annual fixed charges on the capital investments
are based on a 20-year plant life and 4.5 percent
interest charges. This is equivalent to equal annual
charges of 7.7 percent on the capital investment.
The maintenance labor and supplies are based upon
normal operating experience and provide for refrac-
tory replacement every 5 to 7 years, depending upon
the location of the refractory material in the gas
stream. Maintenance charges for boiler and waterwall
surfaces are based on complete tube replacements
every 12 years.
Operating labor varies with 5- to 7-day operation
and with the need for a licensed boiler operator
where pressure fired equipment is included.
City water requirements include an allowance for
spray cooling of the gas stream, quenching of the
ash, and makeup requirements for boiler and cooling
tower operations.
Auxiliary fuel requirements include the fuel re-
quired to maintain ignition of wet refuse in water
cooled furnaces and additional fuel to maintain
steam production where sale of steam is required
when firing wet refuse.
Electric power consumption varies primarily with
the weight of flue gas resulting from different methods
of operation. Electric power also varies with require-
ments for cooling towers and boiler feed pumps.
Operating supplies and chemicals are primarily a
function of boiler makeup requirements and will vary
with the sale of steam.
VALUE OF STEAM FOR SALE
We anticipate that the refractory furnace-boiler
combination of case II should produce an average
of 1.41 pounds of steam per pound of refuse. The
waterwall configuration of case III should produce
an average of 2.61 pounds of steam per pound of
refuse when operated with an average of 60 percent
-------
special studies -for incinerators
69
APPROX. 255'-0°
ID
IO
PLAN OF 4 UNITS
MECHANICAL
CYCLONE
COLLECTOR
ELECTROSTATIC
PRECIPITATOR
INDUCED /\
TYPICAL ELEVATION THRU SINGLE UNIT
FIG. 16. Case IV. Schematic arrangement of a water wall furnace with spray cooling of flue gas.
excess air entering the boiler. Not all of this steam
will be available for sale since approximately 16
percent of the total steam production will be con-
sumed in the deaerating heater to heat the makeup
boiler feed water.
Assuming a weekly quantity of 4,000 tons of refuse
processed by the plant, and the above net production
rates for steam, we have established the following
values for the steam by comparison with the annual
cost for case I.
Case II: $1.06 per thousand pounds available for
sale;
Case III: $0.49 per thousand pounds available
for sale.
These figures do not include the cost of owning and
operating the steam distribution system.
These figures assume that the net steam production
of the plant is sold and no steam generating capability
is lost by operation of the boiler bypass flue in Case II,
01 by condensing operation or operation at higher
excess air levels for case III. These figures can only
apply where the incinerator-boiler plant at full rating
is supplying less than the minimum demand of the
steam system to which it is connected. Operation of
-------
DAY & ZIMMERMANN
TABLE 52
ESTIMATED CAPITAL INVESTMENTS AND OPERATING COSTS,1 INCINERATOR AND INCINERATOR BOILER PLANTS, REFUSE DESIGN CAPACITY
4,000 TONS PER WEEK
Capital costs:
General building construction
Equipment delivered to site .
Mechanical contract
Electrical contract
Total incremental cost
Annual operating expenses :
Operating days pet week
Maintenance labor and supplies
Operating labor
City water
Auxiliary fuel
Electric power
Operating supplies and chemicals .
SUBTOTAL
Fixed charges on investment
Estimated total annual- expense .
Estimated value of steam per 1,000 pounds . .
Case I
Refractory
furnace
$930, 000
$1, 340, 000
$1, 075, 000
$238, 000
$3 583 000
5
$140, 000
$326, 000
$28,000
$161, 000
$1 000
$656 000
$276 000
$932 000
Case II
Refractory
furnace with
boiler
$1, 215, 000
$2, 620, 000
$1, 580, 000
$322, 000
$5 737 000
7
$161, 000
$495, 000
$25, 000
$140, 000
$184,000
$2 000
$1 007 000
$442 000
$1 449 000
$1 06
Case III
Waterwall
furnace with
boiler
$1, 030, 000
$2, 230, 000
$800,000
$237, 000
$4 297,000
7
$147, 000
$495, 000
$43,000
$187, 000
$174, 000
$3 000
$1 049 000
$331 000
$1 380 000
$0 49
Case IV
Waterwall
furnace
$938, 000
$2, 150, 000
$983, 000
$232, 000
$4 303 000
5
$123, 000
$365, 000
$30, 000
$10, 000
$161, 000
$1 000
$590 000
$331 000
$1 021 000
1 Capital investments and operating expenses include only those variables affected by plant design. They are not intended to include all costs
of operation or construction at the incinerator plant.
the incinerator-boiler as the only source of steam to
normal heating and air conditioning system would re-
quire a substantial increase in these cost figures.
SALE OF STEAM AT PROPOSED PLANTSITE
An investigation was made to determine the feasi-
bility of the sale of steam from the proposed No. 5
Incinerator plant. The Potomac Electric Power Co.
operates a steam turbine powered electric generating
station adjacent to the plantsite. They were contacted
to determine if they could use a supply of steam from
the incinerator plant at the 225 p.s.i.g. dry saturated
conditions, available from an incinerator-boiler. We
were advised that they could use 200 p.s.i.g. steam in
their oldet turbines but that superheated steam was
preferred. The minimum cost of steam generation at
the incinerator plant plus pipeline charges is in ex-
cess of the steam generating costs for low pressure
steam at the utility powerplant.
There are no other potential users in the vicinity of
the plant for the quantities of steam available on a
continuous basis.
-------
appendices
APPENDIX C
TYPICAL MUNICIPAL REFUSE ULTIMATE ANALYSES
Refuse component
1 . Newspapers
2 Brown paper
3. Magazine paper
5. Plastic coated paper ....
6 Waxed milk cartons . ...
7 Paper food cartons
8 Junk mail . ...
9 Vegetable food wastes
10. Citrus rinds, seeds
11 Meat scraps cooked
12 Fried fats
13 Leather
14. Rubber composition heel sole
15 Vacuum cleaner
1 6 Evergreen trimmings
17 Flower, garden plants
18 Lawn grass, green ...
19 Ripe tree leaves
21 Wood ....
23 Rags
25 Dirt
26 Metals
'
Percent
as
delivered
10.33
6.12
7.48
25.68
.84
.84
2.27
3.03
2.52
1.68
2.52
2.52
.42
.42
.84
1.68
1.68
1.68
2.52
2.18
2.52
.84
.84
.84
1.68
7.53
8.50
As delivered data
Percent
moisture
5.97
5.83
4.11
5.20
4.71
3.45
6.11
4.56
78.29
78.70
38.74
0
7.46
1.15
5.47
69.00
53.94
75.24
9.97
7.00
24.00
0
0
0
7.00
0
0
0
0
Percent
ash
1.43
1.01
22.47
5.06
2.64
1.17
6.50
13.09
1.06
0.74
3.11
0
21.16
29.74
30.34
.81
2.34
1.62
3.82
.93
2.28
0
0
0
0.93
0
100.00
100.00
100. 00
B.t.u.
pound
7,974
7,256
5,254
7,043
7,341
11, 327
7,258
6,088
1,795
1,707
7,623
16, 466
7,243
10, 899
6,386
2,708
3,697
2,058
7,984
6,999
6,840
15, 910
19, 303
9,580
6,999
12, 780
0
2,660
0
Ultimate analysis — dry basis
Percent
C
49.14
44.90
32.91
43.73
45.30
59.18
44.74
37.87
49.06
47.96
59.59
73.14
42.01
53.22
35.69
48.51
46.65
46.18
52.15
43.9
49.0
78.0
90.0
55.8
43.9
52.1
Percent
H2
6.10
6.08
4.95
5.70
6.17
9.25
6.10
5.41
6.62
5.68
9.47
11.54
5.32
7.09
4.73
6.54
6.61
5.96
6.11
6.1
6.0
9.0
10.0
7.0
6.1
13.1
Percent
02
43.03
47.84
38.55
44.93
45.50
30.13
41.92
42.74
37.55
41.67
24.65
14.82
22.83
7.76
20.08
40.44
40.18
36.43
30.34
49.0
42.0
13.0
37.2
49.0
34.8
Percent
N2
0.05
0
.07
.09
.18
.12
.15
.17
1.68
1.11
1.02
43
5.98
.50
6.26
1.71
1.21
4.46
6.99
Percent
S
0.16
.11
.09
.21
.08
.10
.16
.09
.20
.12
.19
.07
1.00
1.34
1.15
.19
.26
42
.16
71
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DAY
ZIMMERMANN
APPENDIX D
History of East Coast Incinerator-Boiler Installations
Atlanta, Ga. The Mayson plant at Atlanta, Ga.,
contains four International Volund rotary kiln fur-
naces, each followed by a two-drum bent tube boiler
located in the furnace flue. The first two units were
constructed in the early 1940's, followed by two ad-
ditional units in the early 1950's. Flue gas tempera-
tures entering the boilers are in the range of 1,500°
F. to 1,800° F. The original boiler tube life was about
15 years. Steam generated in this plant is sold to a
local steam heating system. The present condition of
the boilers is considered satisfactory. Hand cleaning
is resorted to for removing accumulated tube deposits
during boiler shutdowns about every 2 weeks.
Miami, Fla. The No. 1 plant in Miami, Fla.,
contains six circular hearth batch feed furnaces
divided into two groups of three furnaces each. Each
group of three furnaces has a long common flue with
a secondary combustion chamber at each end. Each
of the four secondary combustion chambers is asso-
ciated with a two-pass boiler. Each boiler is provided
with a gas bypass flue with spray cooling. This plant
was placed in operation in 1955. Flue gas temperatures
entering the boilers average about 1,500° F. Steam
generated in this plant is delivered to an adjacent
hospital. The present condition of the boilers is
considered satisfactory. Hand cleaning of tubes is
performed about four times a year during boiler
shutdowns.
Town of Hempstead, N.Y. The Merrick plant in the
town of Hempstead, N.Y., contains four circular hearth
batch feed furnaces divided into two groups of two
furnaces each. Each pair of furnaces discharges flue
gas through a common secondary combustion chamber
and flue into a boiler. This plant was placed in opera-
tion in 1951 and the boilers were retubed after about
8 years of operation. Flue gas temperatures entering
the boilers vary from 1,200° F. to 2,000° F. The steam
generated is used in the plant for electric power genera-
tion with excess steam going to a condenser. It is
currently reported that approximately 50 percent of
the boiler tubes are being removed to investigate the
effect on tube fouling. The boilers are taken off the
line on alternate weekends for inspection and manual
cleaning.
Providence, R.I. The Field Point plant in Prov-
idence, R.I., contains two fuinaces, each of which
discharges into two boileis. The first two boilers
and furnaces were placed in service in 1936 and retubed
in 1956. The second two boilers and furnaces were
placed in service in 1950. Replacement of the first two
rows of boiler tubes has been maintained on a con-
tinuous basis. Combustion chamber temperatures
range from 1,900° F. to 2,500° F. One boiler and one
furnace are normally operated to provide steam for an
electric generator, which in turn provides power for
the local incinerator and sewage plant. Hand cleaning
of the boilers is performed about every 2 weeks during
shutdown of one boiler associated with the operating
furnace. All of the boilers are currently undetgoing
repairs with steam generation to continue only on a
limited basis.
Oyster Bay, N.Y. The plant at Oyster Bay, N.Y.,
has two boilers, each fired by a pair of rectangular
grate batch feed furnaces. These boilers operated on
a controlled bypass system to maintain desired boiler
pressure. The steam was used for heating and electric
power generation for the plant. The plant was placed
in operation about 1956 and the boilers were retubed
in 1961 because of internal corrosion. Gas temperature
entering the boilers averaged about 1,200° F. Hand
cleaning of the gas side of the boiler was required
about every 4 months. The boilers have been removed
from service.
Boston, Mass. The South Bay plant in Boston,
Mass., has three waste heat boilers. Each is installed
in a flue fed by two rectangular batch feed furnaces.
Boiler bypass flues are provided for each furnace. The
plant was designed to supply steam to a nearby hos-
pital and was placed in operation in 1959. Average
gas temperature entering the boilers is approximately
1,300° F.
Moderate amounts of steam are generated for local
plant use only. The steam supply to the hospital has
been discontinued.
Town of Hemp'stead, N.Y. The Oceanside plant in
the town of Hempstead contains two integral refrac-
tory furnace-convection boiler units with continuous
feed furnaces. This plant was placed in service in
1965- The steam is used to generate electric power fot
use in the plant. The excess steam is used to distill
seawater. Gas temperatures entering this boiler range
upwards from 1,725° F One of the units is presently
out of service for the addition of more retractable soot
blowers and the replacement of some tubes which
have failed, apparently by external damage.
Norfolk Navy Yard. A new incinerator boiler plant
containing two waterwall furnaces with integral
boilers was to be placed in service at the Norfolk
Navy Yard early in 1967. This will be the fiist water-
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special studies for incinerators
73
cooled furnace incinerator boiler plant in the United
States. It is designed to operate at excess air levels
of 50 percent or less when burning refuse. It is equipped
with auxiliary oil firing and will supply port-use
steam (standby service for ships at dock) for the
Navy Yard.
REFERENCES
(1) KAISER, E. R. Chemical analyses of refuse com-
ponents. Paper 65-WA/PID-9. In Proceedings,
American Society Mechanical Engineers, Nov.
7-11, 1965- 5 p.
(2) EBERHARDT, H. European practice in refuse and
sewage sludge disposal by incineration. I. Com-
bustion, 38(3): 8-15, Sept. 1966.
(3) EBERHARDT, H. European practice in refuse and
sewage sludge disposal by incineration. II. Com-
bustion, 38(4): 23-29, Oct. 1966.
00 DEMING, L. F. Navy contemplates steam gene-
rating incinerator. Public Works, 96(7): 92-94,
July 1965.
(5) STABENOW, G. Survey of European experience
with high pressure boiler operation burning
wastes and fuel. In Proceedings, 1966 National
Incinerator Conference, American Society of
Mechanical Engineers, New York, May 1-4,
1966. p. 144-160.
(<5) BENDER, R. J. Incineration plant—plus. Power,
111(1): 62-64, Jan. 1967.
-------
can-metal recovery
ABSTRACT
THIS REPORT reviews the possibilities of recovering
ferrous metal from municipal refuse either before or
after incineration. The study indicates that the only
major existing market for this material (after in-
cineration) is the copper industry which can preferably
use that iron derived from old tin cans. This market
is currently being satisfied.
The capital investment required and the operating
costs to be expected for an installation to recover
ferrous can metal from the residue of a new 800-tons-
per-day incinerator planned for the District of Colum-
bia have been estimated. Because of the low price
obtainable for recovered can metal and the high cost
of freight to the one sizable market, it is concluded
that facilities of this type should not be included in
the new District of Columbia incinerator project.
INTRODUCTION
As THE MAGNITUDE and cost of disposing of solid
municipal refuse continues to grow it becomes more
incumbent on governmental authorities to find ways
of salvaging material of potential value mixed with
the refuse. This is important not only as a means of
reducing the cost of these services but also to conserve
natural resources. One major component of refuse is
steel, especially that from discarded metal cans.
Very little scrap metal is being salvaged by munic-
ipalities. This material is being dissipated in landfills
either as collected with other refuse or as incinerator
residue. Thus this potential source of iron is being
rendered unavailable for future recovery.
The purpose of this report is to study the methods
whereby waste metal may be recovered from refuse
and the economics of the most feasible method, specifi-
cally in relation to Incinerator No. 5 as proposed for
the District of Columbia.
This report does not include the recovery of metal
from shredded bulky objects such as refrigerators be-
cause this type of scrap metal is not adaptable to the
shredded can-metal market.
SUMMARY AND RECOMMENDATIONS
At the present time no satisfactory method exists
for economically extracting scrap can metal from
ordinary municipal refuse prior to incineration. Those
communities that do not have incinerators therefore
discard this can metal in sanitary landfills with their
other refuse.
Ferrous metal can be recovered from incineration
operations provided a complete burnout of the residue
is achieved. The equipment required is relatively
simple but the manpower needed is somewhat costly.
The market for this material is extremely limited and
freight to the point of use generally must be paid by
the shipper.
The largest existing market is for shredded can metal
which is used in copper mining. Since this industry
can readily get as much of this material as it needs, a
buyer's market exists.
The estimated investment cost for a can-metal re-
covery system for the proposed 800-ton-per-day In-
cinerator No. 5 in the District of Columbia is $400,000.
Operating costs including amortization are estimated
to be $13.60 per ton of metal reclaimed. Freight charges
to southwestern United States would add approxi-
mately $83 per ton to this cost. The critical limiting
price including frieght is reported to be $75 per ton.
No guarantee can be made that the sale price for this
metal will increase.
The lack of profit does not justify the capital ex-
penditure required for installation of metal recovery
equipment at this time. It is, however, recommended
that consideration be given in the design of the pro-
posed incinerator plant to the possible future addition
of ferrous metal recovery equipment.
Periodic contacts should be maintained with the
metal market so that if additional markets for re-
covered metal are developed, the necessary equipment
may be installed in this plant.
SOURCE AND QUANTITY OF METAL WASTE
Most municipalities gather tin cans along with
discarded bottles, plastic containers, paper, wood,
75
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DAY & ZIMMERMANN
miscellaneous other metal and sometimes garbage,
in a single collection. Data on the percentage of tin
cans and miscellaneous metal contained is exceedingly
sparse. One source (J) reports a range of values from
3.1 to 11.6 percent by weight for total metal with an
average of about 8 percent. A spot analysis of in-
cinerator residue from four installations in or near
Washington, D.C. (2), indicates that can metal ac-
counted for 63 percent of the ferrous metal present
and that nonferrous metal was less than 1 percent.
This would indicate that nonferrous metal can be
neglected as far as this study is concerned. Applying
the 63 percent can metal in the residue to the 8 percent
overall metal in the rubbish as collected results in a
figure of 5 percent for the overall content of can metal.
Production of refuse in the United States is currently
estimated at 1,600 pounds per year per person (1).
All of this is not necessarily suitable incinerator
charge, however, since it includes residential, com-
mercial, demolition, and industrial refuse. A more
realistic figure for total combustible materials would
be in the order of 800 to 1,000 pounds per year per
person. Thus the potential annual tonnage of scrap
tin plate in refuse may be estimated as follows:
1000 Ibs./capita/yr. x 200,000,000 persons x 5%
lOOOlbs./ton ~ =5,000,000
In 1966 tin plate was being consumed by can manu-
facturers at a rate of 4,900,000 tons per year (3). It
might also be noted that in 1965 a total of 7,331,057
tons of steel was consumed in the form of containers,
packaging, and shipping materials (f). These tonnage.
figures indicate that the percentage figures for metal
in refuse are reasonably accurate.
By the above reasoning it might be concluded that
recoverable metal cans in municipal refuse as collected
would be about 5 percent by weight. However,
experience at specific plants indicates considerable
variation from this figure. These variations are due
to difference in geographical location, the season of
the year, the economic position of the people served
and the specific way in which incinerable refuse is
collected. Data for the first 7K months of 1966 from
a specific plant in Atlanta, Ga., where can metal is
being recovered (j) show an actual yield of 3-78
percent. Therefore, for a planned installation a figure
of 3-5 percent by weight foi design purposes would
be reasonably conservative.
DISPOSAL OF RECOVERED METAL
Ordinary metallic materials encountered in munici-
pal refuse collection operations do not cause special
disposal problems if they are not separated from the
other material. They can be deposited in sanitary
landfills either before or after incineration. But this
type of disposal dissipates a material that has a
potential value.
Considerable quantities of this metal have been
salvaged through the simple expedient of allowing
scrap pickers to gather the material at dumps or
through segregated rubbish collections. The practice
of hand picking metals is rapidly being eliminated
because such activities interfere with satisfactory land-
fill operation. Separation of metals from other refuse
before collection is also declining because it has be-
come politically and economically inexpedient to
require residents to segregate their refuse. But the
overriding cause of abandonment of scrap metal re-
covery has been the high cost of labor and the low
price for which scrap metal can be sold.
Illustrative of the difficulties encountered by muni-
cipalities salvaging can metal is the experience of
Atlanta, Ga., which has been in this business since
1939. In 1956, shredded metal was bringing $270)
per ton FOB Atlanta. By 1966 this price had declined
to $15(5).
The American economy is passing through a phase
in which changes in manufacturing technology have
resulted in low -industrial demand for scrap metal
and increased quality requirements for scrap metal
which industry can use. This situation, however, can
and probably will change in the future. It is therefore
important that this possibility not be overlooked in
planning refuse disposal facilities.
Today's steel industry rejects most scrap from mu-
nicipal collections because it contains too many con-
taminants. The principal objections are the tin plating
and the contents of unshredded cans. Detinning plants
are currently being operated but they will only accept
clean scrap which is produced in can manufacturing
plants. The economics of recovering tin from used
cans are unfavorable.
Can-metal temperatures in the range of 1,400° to
1,500° F. during incineration will cause the tin coat-
ing to be removed but at higher temperatures there
is the possibility of oxidation of the thin parent metal
which will degrade the value of the product. When
can metal is processed at acceptable temperatures and
shredded, it is acceptable to the copper industry
(jee below) but elsewhere it cannot compete with
the abundance of iron and steel melting scrap resulting
from the demolition of automobiles and other bulky
objects.
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special studies for incinerators
77
It is important to note that nearly all scrap metal
users prefer shredded metal to metal compressed into
bales. The principal reason for this is that the final
scrap product can be passed through a magnetic sep-
arator which will reject contaminants not hitherto
eliminated. For this reason the trend in commercial
scrap yard operation is toward the use of shredders
in place of baling presses.
A big disadvantage of shredded material as com-
pared to baled metal is the low bulk density. This is
especially true in the case of can metal. Shredded
cans have a bulk density of 20 to 25 pounds per cubic
foot compared to 150 pounds per cubic foot for baled
metal. This is an important factor in the high cost of
shipping shredded can metal.
Some markets of limited demand for shredded can
metal are understood to exist in the eastern United
States for end uses such as the manufacture of ferro-
alloys, but information on these markets is very
meager.
The only significant market at present for this type
of scrap is the copper mining industry which is
centered principally in our western States and Mexico.
This market cannot absorb all the scrap metal that
can be salvaged, therefore the buyer can be very
particular about the quality of the material accepted.
The scrap steel is used in a copper leaching process in
which the ratio of exposed metal surface to the bulk
involved should be as high as possible. Shredded metal
cans are admirably suited for this use compared to
other forms of steel scrap. Thus, it is desirable to re-
move any heavy iron that may be recovered and also
to shred the cans before shipping the product to be
used for this purpose.
Competition for the available market also makes it
necessary for the seller to absorb the freight charges.
The shredded metal is heaped in open gondola cars
but, as stated previously, the bulk density results in
abnormally high freight rates. A figure of $4.15 per
cwt. from Washington, D.C., to either Arizona or
Utah has been quoted by a major eastern railroad (6).
Prices paid during 1966 at copper mines in the south-
western United States ranged from $52 to $62 per ton
of reclaimed can metal delivered. The critical limiting
price is estimated to be about $75 per ton for top
quality material (7). It is evident that the freight
charges from Washington, D.C., to the delivery point
would exceed the current selling price for this re-
claimed scrap.
Because the copper companies need large and
particularly stable sources of supply, they frequently
contract with scrap metal firms specializing in this
type of metal. A list of copper and scrap metal firms
who are in the market for incinerated can metal is in-
cluded as appendix F. It is apparent that firms in the
scrap metal salvage industry possess considerable
proprietary information as to the nature and mag-
nitude of the scrap metal market which is not available
to the general public. A national association of the
scrap iron and steel processing industry has offered the
benefit of their considerable knowledge in the field of
scrap (#).
AVAILBALE METAL RECOVERY METHODS
Before Incineration
The only proven method of segregating metal from
solid waste as collected is by the use of manual pickers.
The economics of this operation obviously are depend-
ent on the cost of labor and the market for the re-
covered metal.
Attempts have been made to use a magnetic sepa-
rator for this purpose but the lack of homogeneity
and low metal concentration in the charge material
has resulted in an extremely inefficient operation.
On the west coast the value of scrap metal is higher
and smog conditions are severe. The smog conditions
have restricted the use of incineration and as a result,
attempts have been made to remove metal with a
mechanical picker or sorter. However, there is no
known successful installation. Further consideration
of metal salvage before incineration will require
development of a suitable method of mechanical
separation of refuse and metal.
After Incineration
The recovery of ferrous metal from incinerator
residue is feasible and profitable under certain condi-
tions. It is being practiced at a number of incineration
plants in different parts of the country (see app. F).
Of the 11 plants currently in operation, it should
be noted that seven are of the rotary kiln type and
that three new plants under construction are also of
this type. This is attributable to the high quality of
burnout of residue that can be achieved in this type
of design. However, this does not rule out other
continuously fed incinerators of modern design which
can achieve an equally good burnout.
An acceptable procedure for recovering the metal
is to first pass the furnace ash residue from the in-
cinerator over screens wheie the nonmetallic ash type
of material is washed from the cans and discharged
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DAY & ZIMMERMANN
through the screen surface into residue trucks for
hauling to a landfill. Rotary screens aie preferred
over the vibrating type. The latter work best when
the solid material being retained is roughly spherical
in shape and bounces easily. The rotary screen is not
hampered as much by jagged points of metal catching
in the screens.
The washed can material in a typical installation
is discharged from the ends of the rotary screens into
a drag conveyor which elevates the cans and dis-
charges them into a storage bin. This storage bin is
installed in the plant to permit the operation of the
metal shredding and separation system on an 8-hour-
per-day, one-shift basis. Normally there is not enough
can metal to justify the labor costs of a three-shift
operation of the entire system.
A constant inspection must be made of all residue
entering the rotary screens to remove material such
as wire, heavy metal, and masonry, which might
foul the screens, interfere with subsequent operations
or degrade the product. Also, residue containing large
amounts of unburned refuse as a result of improper
incinerator operation can cause difficulty at the wash
screens.
Material is removed from the can storage bin
during the day and fed continuously to a can shredder.
This machine employs rotating hammers to tear the
cans by impact and discharges the pieces through a
grate which will pass metal objects of the size
acceptable to the purchaser. The processed material
then passes through a magnetic separator where the
nonmagnetic material is discharged for removal from
the system. The magnetic material is transported to
a car or truckloading hopper (figure 17).
CAPITAL INVESTMENT AND OPERATING COSTS
It is estimated that the additional equipment
required to process the residue from the proposed
Incinerator No. 5 in order to recover can metal could
be purchased and erected for $400,000 as tabulated
below:
Site preparation and complete structures.
Equipment, installed including electrical.;.
Railroad siding
Engineering including field inspection and supervision.
Contingency and escalation
$111, 000
192, 000
25, 000
24,000
48, 000
400, 000
building. The estimate is based on this type of
installation without an enclosure or architectural
treatment.
Estimated annual operating expenses would total
$99,350 as shown below.
Inspection at rotary screens (1 laborer, 3 shifts) $18, 000
Day-shift operator labor (2 operators, part-time foreman). 18, 850
Maintenance 8, 400
Electric power 3, 500
Subtotal 48,750
Annual fixed charges (10-year life at 4l/2 percent interest).. 50, 600
Total annual operating expense 99, 350
Using the figure of 3-5 percent by weight mentioned
earlier in this report as the quantity of can metal
that can be recovered based on incinerator charge,
the new 800-ton-per-day incinerator plant would
produce 28 tons of shredded can metal per day.
When operating 5 days per week and 52 weeks per
year, the annual production would be 7,300 tons.
Therefore the cost of recovering can metal would
be $13-60 per ton including amortization charges.
APPENDIX E 1
INCINERATORS PRACTICING METAL SALVAGE
Location
Atlanta, Ga
Quebec, Province of
Quebec.
Louisville, Ky
Chicago, 111
Atlanta, Ga. . . .....
Broward County,
Fla.2
Do.2
Chicago, 111
Do
Do
Do
Tampa, Fla
Dayton, Ohio.
De Kalb County, Ga.
Plant
Mayson
Southwest
Hartsfield
No. 1
No. 2
Stickney
(Private).
Bolda (Private) .
Medill
Calumet
Montgomery
County.
Year
built
1939
1955
1957
1963
1963
1964
1964
1958
1956
1959
3 1967
3 1967
3 1967
Type furnace
Rotary kiln.
Batch circular.
Rotary kiln.
Do.
Do.
Con tin.
recip.
Do.
Rotary kiln.
Do.
Batch, rock.
grate.
Rotary kiln.
Do.
Do.
Do.
These costs are based on the layout shown in figure
17. It is perfectly feasible to erect most of this equip-
ment on open steel framing outside of the incinerator
1 Data from Bureau of Mines, College Park, Md.
2 Currently metal recovery not in operation due to lack of market
for product. No provision at these plants for washing or shredding
of cans from residue.
3 Not completed. Planned metal salvage facilities.
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ROTARY
SCREENS
(ASH DISCHARGED TO
TRUCKS LOCATED
BELOUI SCREENS)
FEED POINT FOR
INCINERATOR RESIDUE
<1
i:
a
R.
RAILROAD CAR OR
TRUCK LOADING
LOCATION
-AS REQUIRED FOR
LOCAL R.R, CLEARANCE
FEED CONVEYOR NO.I
ELEVATION
FIG. 17- General arrangement of can-metal recovery system.
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DAY 5; ZIMMERMANN
APPENDIX F
PRIVATE FIRMS IN THE SCRAP METAL INDUSTRY
Proler Steel Corp., 5200 Clinton Drive, Houston, Tex.
Edward Levy Metals, Inc., New Orleans, La.
Los Angeles By-Products Co., 1810 East 25th Street,
Los Angeles, Calif. 90058.
Southern Federal Alloys, Chattanooga, Tenn.
REFERENCES
00 AMERICAN PUBLIC WORKS ASSOCIATION. Municipal
refuse disposal. Chicago, Public Administration
Service, 1966. 528 p.
(2) Private communication.
(3) U.S. DEPARTMENT OF COMMERCE. Current in-
dustrial reports—metal cans, June 1966.
00 AMERICAN IRON AND STEEL INSTITUTE. Table 24,
Shipments of steel products by market classifica-
tion. In Annual statistical report, 1965.
(5) Private communication, Atlanta, Ga.
00 Private communication, Pennsylvania Railroad.
(7) Private communication, U.S. Bureau of Mines.
0?) Private communication, Institute of Scrap Iron
and Steel, Inc., 1729 H Street NW., Washington,
D.C. 20006.
U.S. GOVERNMENT PRINTING OFFICE : 1968—0-289-620
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