EN
L HEALTH SERIES
Air Pollution
AIR POLLUTION
Ai> 1/5^4' I **
TEPEE
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
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AIR POLLUTION ASPECTS OF TEPEE BURNERS
USED FOR DISPOSAL OF MUNICIPAL REFUSE
Thomas E. Kreichelt
Technical Assistance Branch
Robert A. Taft Sanitary Engineering Center
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Division of Air Pollution
Cincinnati, Ohio
September 1966
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The ENVIRONMENTAL HEALTH SERIES of reports was estab-
lished to report the results of scientific and engineering studies of
man's environment: The community, whether urban, suburban, or
rural, where he lives, works, and plays; the air, water, and earth
he uses and re-uses; and the wastes he produces and must dispose oi
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tion on the intramural research activities of programs and Centers
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are
AP Air Pollution
AH Arctic Health
EE Environmental Engineering
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WP Water Supply
and Pollution Control
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Public Health Service Publication No. 999-AP-28
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CONTENTS
Page
ABSTRACT v
INTRODUCTION . 1
CONCLUSIONS AND RECOMMENDATIONS 1
CONSTRUCTION AND OPERATION OF A TEPEE BURNER. 2
AIR POLLUTION FROM TEPEES BURNING MUNICIPAL
REFUSE . 5
Effect of Charging Methods 5
Effect of Tepee Burner Construction 10
Effect of Tepee Burner Operating Practices ....... 14
Effects of Various Charges and Charging Rates 14
Effect of Clean Out Operation 16
ECONOMIC AND OPERATIONAL COMPARISON ........ 19
LAND USE REQUIREMENTS 21
EQUIPMENT AVAILABLE TO CONTROL FLY-ASH AND
SMOKE EMISSIONS 22
COMPARISON OF TEPEE REFUSE BURNER WITH OTHER
METHODS OF MUNICIPAL WASTE DISPOSAL 22
Tepee Initial Cost 22
Sanitary Landfill 23
Multiple Chamber Type 23
Cost Comparison 24
ACKNOWLEDGMENTS . 25
REFERENCES 27
APPENDIX ... 29
iii
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ABSTRACT
This report covers an evaluation study of air pollution emis-
sions based upon an extensive literature search and field trips to 15
tepee burners in six states. Smoke as a function of composition and
rate of charge was observed, and the effect of burner charging methods,
construction, and operational procedures on smoke emissions recorded.
None of the tepee incinerators observed in operation meet normal
visible emission limitations of air pollution control ordinances of most
municipalities. Nuisance problems from fly-ash fallout can be ex-
pected within distances of up to 1,290 feet downwind from an operating
tepee.
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INTRODUCTION
During the last several years, a large number of tepee-type
industrial waste burners have been adapted to municipal refuse dis-
posal and used across the country. Numerous public complaints
prompted municipalities and states to ask the Public Health Service
for an opinion on the advisability of using tepee burners for muni-
cipal refuse disposal. The Technical Assistance Branch, Division
of Air Pollution, Public Health Service, consequently, undertook a
study (including air pollution emissions and some economical as-
pects) to evaluate the use of tepee burners for disposal of municipal
refuse. Based upon the results of the study, the Public Health Ser-
vice does not consider the use of tepee refuse burners as a suitable
method for the disposal of municipal refuse.
The evaluation study, which is reported herein, was based upon
an extensive literature search and field trips to 15 refuse burners
in six states. Smoke as a function of composition and rate of charge
was observed, and the effect of burner charging methods, construction,
and operational procedures on smoke emissions recorded. The in-
formation presented is intended to assist municipalities not now using
tepee refuse burners in determining the ability of the tepee burner to
fulfill their needs, both in refuse disposal operations and in air pol-
lution control; and furthermore, to give municipalities that presently
operate burners data they can use to improve burner operations and
reduce air pollution emissions.
CONCLUSIONS AND RECOMMENDATIONS
A number of cities of less than 100,000 people use tepee
burners for disposal of municipal refuse. Field observations of
15 tepee burners used for disposal of domestic and/or industrial
waste indicate that none of the tepee incinerators observed in oper-
ation meet normal visible emission limitations of air pollution control
ordinances of most municipalities, i.e., an allowance of a visible
emission as dark or darker than Number 2 Ringelmann or the equi-
valent opacity for periods not greater than from 3 to 8 minutes in any
1 hour. Also nuisance problems from fly-ash fallout can be expected
within distances of up to 1,290 feet downwind from an operating tepee,
and at possibly greater distances depending upon wind speed and
burner operating conditions. For these reasons, it is necessary
both to bring tepee burners now in use up to the highest possible
standards of performance and, wherever possible, to replace them
with better methods of municipal refuse disposal.
Where communities continue to operate tepee burners, the fol-
lowing guidelines are recommended for improving combustion in the
tepee burner and for reducing incidence of nuisance complaints,
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regardless of other air pollution measures in effect.
1. The burner should not be built within 1,500 feet of the nearest
property line (equivalent to approximately 200-acre site).
2. The surrounding property should be zoned agricultural or
heavy industrial.
3. The burner should be charged by means of a covered con-
veyor belt.
4. A receiving building with a floor conveyor should be used
for charging refuse to the conveyor belt.
5. Materials that produce heavy smoke when burned, i.e.,
rubber, plastics, asphalt or leather products, should be
removed from the conveyor charge and disposed of by
landfill.
6. Refuse should not contain more than 15 to 20 percent (by
weight) garbage, and the garbage should be mixed uniformly
with dry combustible refuse.
7. The capacity of the underfire air blower should ensure com-
plete combustion so that the ash will be cold during cleanout
operation. (The manufacturer should provide instructions
for use that will ensure complete combustion.)
8. The ash should be pushed just outside the burner doors where
it can cool and be wetted before being placed in a sanitary
landfill.
9. The burner and equipment should be inspected and repaired
under a continuous maintenance program.
Not listed above, but found to be of crucial importance in ef-
fective operation of the tepee refuse burner is an operator who is
highly conscientious in the performance of his duties.
CONSTRUCTION AND OPERATION
OF A TEPEE BURNER
The tepee burner is so called because of its similarity in shape
to an Indian tepee. The size of a burner may vary from 10 feet in
diameter by 12 feet high to 90 feet in diameter by 97 feet high. A
typical size for the 15 tepee burners inspected was 52 feet in diameter
by 57 feet high. (See Figures 1 through 6.) The base of the tepee
burner is normally secured to a concrete ring foundation, and the
walls are usually 16-gauge steel. Many tepees have an inner-wall
liner of corrugated steel for protection from heat. The 15- to 20-foot
2 Air Pollution Aspects
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diameter dome of the tepee is normally equipped with 2-1/2-mesh
steel wire for collection of large particles of fly ash. A large number,
e.g., 50 to 75, adjustable- or fixed-draft doors about 10 inches wide by
20 inches high are located at the base of the burner to provide over-
fire air for combustion. Most tepee burners are also equipped with
forced-draft blowers and underground piping to the burner grate.
Double doors large enough for a dump truck to pass through provide
access for charging the tepee with combustible waste and for removing
ash.
Three methods are used for charging refuse to the tepee burner:
(1) by steel conveyor belt, (2) by bull dozer with a movable blade, and
(3) by elevated truck chute. (See Figures 1 through 4.) Table 1 de-
scribes each of the tepee burners inspected, and Table 2 shows a
summary of grate and door types and kinds of refuse burned based
on feed methods.
The fastest charging requiring the least operating personnel is
the elevated-truck-chute method. The incoming truck loaded with re-
fuse backs onto an elevated platform to the tepee charge chute and
dumps the refuse onto the chute and into the tepee. Incoming truck
loads of refuse may vary from one to four per hour.
A typical operating schedule observed during the study was
from 7:00 a.m. to 6:00 p.m., 6 days per week. The first operation
of the day is removal of the ash residue from the previous day. The
ash is loaded on a truck and hauled to a landfill. Ash removal from
the tepee may take from 30 to 60 minutes. After the tepee is charged
with municipal-type refuse, the charge is ignited, and the underfire
air blowers are turned on.
The more popular type of charging observed during this study
was the dozer method. The incoming truck dumps the full load of
refuse in front of the open doors of the tepee. A large dozer pushes
the refuse.onto the burning pile in the center of the tepee. The dozer
blade is raised vertically as the dozer moves forward. At most of
the dozer-fed tepees, the large dozer was operating about half and
the large double doors were open approximately three-fourths of the
operating day. A smaller dozer was usually used while the large
dozer was serviced or repaired.
The typical conveyor-feed system for a tepee includes both a
covered 4-foot-wide conveyor belt and a receiving house, perhaps 40
by 60 by 20 feet high. The base of the loading house is often 10 to
15 feet above the floor of the tepee burner. The belt conveyor enters
the tepee about half-way between its base and dome and extends into
the center of the tepee. Incoming trucks unload refuse onto the floor
of the receiving building. A small dozer pushes refuse onto a separate
floor conveyor, which transfers the refuse to the inclined conveyor
feeding the tepee. This type of charging system offers a better con-
trolled, uniform feed. The large unloading doors on the tepee are
Of Tepee Burners
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Table 1. DESCRIPTION OF TEPEE REFUSE BURNERS INSPECTED
Feed method
Dozer
Dozer
Dozer
Dozer
Dozer
Dozer
Dozer
Dozer
Dozer
Conveyor
Truck chute
Dozer
Conveyor
Conveyor
Dozer
Burner size
(diameter x height) ,
feet
53 x 57
45 x 50
53 x 57
67 x 72
53 x 57
87 x 73
67 x 73
53 x 57
53 x 57
80 x 87
45 x 50
40 x43
67 x 73
53 x 57
53 x 57
Burner
age,
years
5.5
2.2
2.2
2.2
2.3
2.5
2.4
3.0
3.6
1.5
1.5
3.8
1.2
3.0
4.0
Burner use
Municipal waste
Industrial waste
(everything)
Industrial waste
(wood and paper)
Industrial waste
(mostly wood & paper)
Industrial and
municipal
Industrial (wood
and paper)
Municipal (some
industrial)
Municipal
Municipal
Municipal
Industrial-
municipal
Municipal
Municipal
Municipal
Municipal -
industrial
Auxiliary
equipment
in use
2 blowers
none
none
none
2 blowers
none
2 blowers
2 blowers
2 blowers
1 blower
2 blowers
none
2 blowers
2 blowers
Afterburner
and scrubber
Clean-out
procedures
Push out cold ash
Push out hot ash
Push out hot ash
Wet down,
push out ash
Push out hot ash
Push out warm ash
Carry out hot ash
Push out hot ash
Push out hot ash
Push out cold ash
Push out hot ash
Push out hot ash
Carry out hot ash
Push out hot ash
Push out ash
£
I—I
o
!3
•s
fD
O
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Table 2. TEPEE BURNER COMPARISON BASED
ON FEED METHOD
Feed
method
Conveyor
Truck chute
Dozer fed
Total
Number of burners
Total
3
1
11
15
Kind of refuse
burned
Municipal
3
0
5
8
Industrial
0
0
1
1
Both
0
1
5
6
With underfire
grate
Installed
3
1
10
14
Operating
3
1
5
9
With
usable
doors
3
1
3
7
closed during charging and burning to afford better control of over-
fire air entering the louvers at the base of the tepee.
Although the charging of refuse may stop at about 5:00 p.m.,
the burning continues at a reduced rate for another 8 to 12 hours.
The forced-draft blowers are left operating to provide the necessary
underfire air to complete combustion. Although the ash residue is
normally removed each morning, in some tepee burners ash is re-
moved only once or twice a week. In most of the ash unloading oper-
ations, no unburned garbage was detected.
AIR POLLUTION
FROM TEPEES BURNING MUNICIPAL REFUSE
There are six main operating variables that can affect the com-
bustion efficiency adversely, thus increasing air pollution emissions
of a tepee refuse burner: (1) charging methods, (2) burner construction,
(3) burner operating practices, (4) composition of charge material,
(5) charging rate, and (6) tepee clean-out operation.
EFFECT OF VARIOUS CHARGING METHODS
Dozer. As indicated previously, control of the overfire air in a
tepee burner requires that the large loading and unloading doors be
closed. The overfire air should enter only through the louvered
openings at the base of the tepee in a tangential pattern, which induces
the combustion products and fly-ash to move clockwise around the
fire. This flow pattern holds the combustible material in suspension
and promotes more efficient combustion. When the doors are open,
the circular motion of the draft stops and the combustion gases cool.
As a result more smoke and fly-ash are emitted from the top of the
tepee burner, and fly-ash and dust blow through the open doors.
Whenever a dozer is charging a tepee burner, the large double doors
Of Tepee Burners
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of the tepee must necessarily be open. Operation at near capacity or
above, therefore, requires open doors almost constantly.
From an air pollution standpoint, the use of a dozer to feed re-
fuse to a tepee is a very poor method (Figures 1 and 2). Table 3
Figure 1. Typical dozer-fed refuse burner. Charge is damp paper and wood. Note refuse guides
attached to protect tepee entrance, prevent doors from being used.
lists the visible emissions observed from two typical dozer-fed tepee
burners. Burner No. 1, burning wood and dry paper, operated with
a discharge plume of greater than 40 percent equivalent opacity for
45 minutes during 1 hour's observation. The underfire air blowers
were not operating, a typical practice for tepees burning paper and
wood. Even with the underfire air blowers operating full time,
Burner No. 2 emitted heavy smoke and a resulting discharge plume
greater than 40 percent equivalent opacity when burning domestic
refuse.
Air Pollution Aspects
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Figure 2. Tepee refuse burner being fed by dozer. Note torn door opening and operator driving
unprotected into fire.
Elevated Truck Chute. An elevated truck-chute burner (Figure
3) is an even less acceptable means of burning refuse than the dozer-
fed burner from the aspect of air pollutant emissions. When refuse
is dropped on the burning pile, the fire is smothered and the refuse
burns with a heavy discharge of smoke and fly-ash. By the time the
fire is burning well again, another load is dropped, and the smoulder-
ing and smoke recur.
Only one-truck-chute fed tepee was observed in operation.
Visible emissions from this burner (Table 4) varied from 4 to 5
Ringelmann No. when leather, paper, and wood were burned and
between No. 3 to 3-1/2 when only paper and wood were burned. Two
forced-draft blowers continually supplied underfire air to this burner.
Conveyor. Combustion is more complete in a conveyor-fed
tepee, (Figure 4) than in the dozer- or truck-chute-fed burners be-
cause of a more uniform feed rate and better control of overfire air.
Although the visible emissions listed in Table 5 for Burner No. 1
were generally greater than 40 percent equivalent opacity, they did
not exceed 65 percent. The effect of excess overfire air can be seen
in the opacity readings for Burner No. 2. When the unloading doors
were open during the charging of wood and paper boxes, the discharge
Of Tepee Burners
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Table 3. VISIBLEHMSSIONS OBSERVED FROM TWO
TYPICAL DOZER-FED TEPEE BURNERS
Time
Burner No. 1
9:00 - 9:15 a.m.
9:15 - 9:30
9:30 - 9:45
9:45 - 9:50
9:50 - 9:55
9:55 10:00
10:00 10:15
Burner No. 2
2:30 - 2:45 p.m.
2:45 3:00
3:00 3:15
3:15 - 3:30
Average
Ringlemanna
No. or percent
equivalent opacity
3-1/2
3
2-1/2
2
1-1/2
1
3-1/2
50
60
100
80
Color of
plume
Grey
Grey
Grey
Grey
Grey
Grey
Grey
White
White
White
White
Material
charged
Wood and dry paper
Wood and dry paper
Wood and dry paper
Wood and dry paper
Wood and dry paper
Wood and dry paper
New charge of wood
and dry paper
Domestic refuse
Domsstic refuse
New charge,
domestic refuse
plus wet garbage
New charge,
domestic refuse
plus wet garbage
aNo. 5 Ringlemann is a solid grey or black plume or a plume which
entirely obscures vision. No. 1 Ringlemann is a light grey plume
or a plume which reduces visibility through the plume by :
(Equivalent opacity of 20% - equal to opacity of a grey plume of
No. 1 Ringlemann).
Air Pollution Aspects
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Figure 3. Truck-fed tepee refuse burner. Charge is of dry paper,
wood, and minor industrial waste.
Table 4. VISIBLE EMISSIONS OBSERVED FROM A
TRUCK-CHUTE-FED BURNER
Time - p.m.
9:00 - 9:15
9:15 - 9:30
9:30 - 9:45
9:45 - 10:00
Average
Ringlemann
No. a
5
4
3-1/2
3
Color of
Plume
Black
Dark grey
Dark grey
Dark grey
Material
charged
Leather, paper,
and wood
Leather, paper,
and wood
Paper and wood
Paper and wood
aNo. 5 Ringlemann is a solid grey or black plume or a plume which
entirely obscures vision. No. 1 Ringlemann is a light grey plume
or a plume which reduces visibility through the plume by 20%
(Equivalent opacity of 20% - equal to opacity of a grey plume of
No. 1 Ringlemann).
Of Tepee Burners
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plume was a No. 5 Ringelmann. When the doors were closed, the
opacity of the plume dropped to between a No. 1-1/2 and 3-1/2 Ringel-
mann. Underfire air was utilized in both conveyor-fed tepee burners.
Figure 4. Conveyor—fed municipal refuse burner during startup operation. Charge is dry paper,
wood, and small amount of garbage. Represents peak emissions during field visit to
this site.
EFFECT OF TEPEE BURNER CONSTRUCTION
Proper tepee burner construction and maintenance is a prere-
quisite to optimum burner operation and minimum air pollution. Most
of the construction difficulties arise around the forced air system,
which must be installed for adequate combustion. Of primary im-
portance is the location of the grates and the method by which they
are placed in the burner floor. The grates (8 to 12) should be placed
very close to the center of the burner so that they will be covered
completely as the combustible material falls from the conveyor chute.
If the grates are located at the edges of the burning pile, they are vir-
tually ineffective since the forced air is more likely to channel through
several grates while avoiding the bulk of the pile.
To avoid tearing the grates from the burner floor with the clean-
out dozer, the grates should be set in a ring of concrete approximately
20 to 30 feet in diameter, depending upon the burner size. The con-
crete should not have reinforcing material in it so that it can expand
and contract freely without cracking. It should have beveled edges so
that the clean-out dozer blade will easily ride over the surface. The
remaining floor area should be dirt.
Most tepee burners observed did not have a forced-draft blower
that could move a sufficient flow of combustion air through heavily
packed refuse piles. The only blower installation that appeared to work
10
Air Pollution Aspects
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Table 5. VISIBLE EMISSIONS OBSERVED FROM TWO
TYPICAL CONVEYOR-FED TEPEE BURNERS
CHARGED WITH HOUSEHOLD REFUSE
Time
Burner No. 1
11:30 11:35 a.m.
11:35 - 11:40
11:40 - 11:45
11:45 11:50
11:50 - 11:55
11:55 - 12:00
12:00 - 12:05
12:05 - 12:15
12:15 12:25
12:25 12:30
Burner No. 2
3:20 - 3:35 p.m.
3:35 - 3:40
3:40 - 3:45
3:45 - 3:50
3:50 - 4:05
4:05 - 4:20
Average
Ringelmanna
No. or percent
equivalent opacity
40
50
55
60
55
60
65
55
50
45
5
4-1/2
3-1/2
3
2
1-1/2
Color of
plume
White
White
White
White
White
White
White
White
White
Wnite
T_
Black0
Black0
Dark grey
Dark grey
Light grey
Light grey
No. 5 Ringelmann is a solid grey or black plume or a plums which
entirely obscures vision. No. 1 Ringelmann is a light grey plume
or a plume which reduces visibility through the plume by 20%
(Equivalent opacity of 20% - equal to opacity of a grey plume of
No. 1 Ringelmann).
"One load of paper and cardboard boxes added by dozer.
°Dozer loading stopped and unloading doors closed.
effectively had a rated capacity of 15,000 to 20,000 cubic feet of air per
minute. The tepee burner manufacturers should themselves confirm or
deny this figure by means of simulated tests on heavily packed piles.
When the blower capacity is not sufficient, the air flows through one
grate or stops completely. In some cases, the duct openings are clog-
ged with ash and molten metal.
A number of municipalities have purchased tepee burners of a
lower capacity than needed in order to reduce the initial capital expense.
In time, the burners become increasingly overloaded, resulting in
burner damage beyond feasible repair, and in increased emissions of
smoke and fly-ash. This type of damage arises in two forms: first,
Of Tepee Burners
11
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Figure 5. Dozer-fed tepee refuse burner with torn walls, no screen on top, no doors, and
unprotected blowers. Burner is less than 4 years old.
Figure 6. One of four dozer-fed tepee burners of comparable condition,
each slightly over 2 years old.
12
Air Pollution Aspects
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the walls twist and crack from being overheated; second, the walls and
doors are often hit and torn by the clean-out dozer because of limited
dozer maneuverability. In addition, combustion efficiency is reduced
because of the shortage of underfire combustion air. These factors
result in greater smoke and fly-ash emissions. The burner operator
then finds that the lifetime of the burner has dropped to 5 years or
less. Note the age of the burners shown in Figures 5 and 6.
In most tepee refuse burner installations, the dome opening at
the top is covered by 1/4-inch-wire mesh to prevent large fly-ash
particles from leaving the burner. The fly-ash may clog the screen
and limit the amount of combustion air passing through it. Some
manufacturers have covered part of the dome with 1/2-inch screen
to let more air and more fly-ash pass through. The undesirability of
this type of screen is demonstrated by a picture (Figure 7) of fly-ash
(emitted in a 5-hour span from this type of dome) in a footprint on
fresh snow, 1,000 feet downwind from the burner. A possible solution
would be to place a 1/2-inch horizontal screen below the 1/4-inch dome
screen to keep all fly-ash larger than I/2-inch in diameter from
clogging the 1/4-inch screen.
Most burner operators using conveyor belts obtained satisfactory
operation by using a 4-foot-wide steel belt, which has been found to
handle most refuse with a minimum of hand charging. A steel belt is
Figure 7. Fly-ash collected in 5 hours, in footprint in fresh snow 1,000 feet downwind from
conveyor—fed refuse burner.
not very likely to tear or break and should last the life of the burner.
It is also built to promote continual flow of refuse to the burner without
occasional blockages along the belt passage.
Of Tepee Burners
13
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EFFECT OF TEPEE BURNER OPERATING PRACTICES
A tepee burner is no better than the reliability of the operator.
In 1 day an operator can burn holes in the walls, tear off the doors
by hooking them with the clean-out dozer, or tear out the grates with
the dozer blade (Figures 5 and 6). On the other hand, when the oper-
ator is conscientious, the burner can be expected to last for the de-
preciation period of 10 years with a minimum of repairs. At not
more than a third of the sites visited could the operators have been
described as conscientious workers; in every case where the oper-
ators were not conscientious, the burners were emitting excessive
smoke and fly-ash. This is not to say that in every case in which
the burner is in poor condition, the operator is not conscientious;
the burner condition is also dependent upon the operating instructions
provided by the owner.
For more effective air pollution control, the operator should
adhere to certain operating practices. He should regulate the feeding
rate of the conveyor system so as not to smother the fire. He should
keep materials that adversely affect the quality of combustion from
being charged into the burner (see next section). Finally, he should be
extremely careful when moving the ash from the burner during the
clean-out operation to keep particulate matter from blowing onto the
property of others.
EFFECT OF VARIOUS CHARGES AND CHARGING RATES
The extent of air pollution at a burning site is highly dependent
upon the type of material being burned and the rate at which this mater-
ial is charged to the burner.
Composition of charge. Some materials should not be charged
into a tepee refuse burner. Others should be charged only as a small
percentage of a homogeneous mixture. Table 6 lists the types of mate-
rials that should and should not be fed into a tepee burner. All plastic,
rubber, asphalt, and leather goods burn with a resulting smoke emission
of a No. 5 Ringelmann or a 100 percent equivalent opacity regardless
of the method of charge. Almost every experienced tepee burner oper-
ator questioned during the field observations felt that these materials
should not be burned in a tepee. Most of the operators segregated
this material and disposed of it by landfill. A typical example is shown
in Figure 8 of a tepee burning plastic materials.
If the refuse contains garbage over 15 to 20 percent by weight,
and if this percentage is not mixed fairly uniformly with dry refuse,
heavy smoke emissions, i.e., No. 4 or 5 Ringelmann, will generally
occur. In practice mixing wet and dry refuse uniformly at the tepee
site is not feasible with either the truck-chute or dozer-type charging
technique, but can be done either manually or by use of a small dozer,
in a conveyor-fed unit equipped with an unloading house having a floor
conveyor. In the latter case the density of smoke is not significantly
more than that from burning dry refuse. Wherever possible, however,
14 Air Pollution Aspects
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Table 6. EFFECT OF VARIOUS MATERIALS ON
TEPEE REFUSE BURNER OPERATION
Maximum
recommended
percent of
material Basis of
Material in charge recommendation
Dry Wood 100
Dry paper 100
Damp paper 30
Brush, logs 100
Ashes None
Plastic products None
(polyvinyl
chloride, etc. )
Rubber products None
Asphalt products None
(tar paper, lin-
oleum tar blocks,
etc.)
Leather products None
Raw garbage 15
-
Tends to smother pile;
makes for unsatisfac-
tory hot clean-out
operation.
Ashes from home use
placed in charge
produced Ringelmann
No. 3 to 4 smoke.
Produces Ringelmann
No. 5 or 100% equiva-
lent opacity smoke
accompanied by
nauseating odors.
Produces Ringelmann
No. 5 or 100% equiva-
lent opacity smoke,
sometimes accompanied
by odors.
Produces Ringelmann
No. 5 or 100% equiva-
lent opacity smoke.
Produces copious
quantities of
Ringelmann No. 5 smoke
lasting for hundreds
of yards downwind.
Tends to smother pile;
makes for unsatisfac-
tory hot clean oper-
ation; may cause
extensive odors.
Practical experience
of nine
municipal operators
-
-
Damp material cuts
down on burner
capacity; must be
charged sparingly.
-
Very little effort to
separate ashes from
charge.
Eight of nine munici-
palities recognized
adverse effects and
put plastic products
in landfill. a
Eight of nine muni-
cipalities recognized
adverse effects and
put rubber products
in landfill. a
Eight of nine munici-
palities recognized
adverse effects and
put asphalt products
in landfill. a
Only occurs around
leather product cor-
porations.
All convey or -fed
burner operators rec-
ognize that only small
amounts of garbage may
be mixed homogeneously
with dry combustible
material. If possible,
dispose of all garbage
by other means.
The ninth municipality paid little attention to tepee burner operations and did
not attempt to control charge composition under any circumstance.
Of Tepee Burners
15
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raw garbage should be buried in a sanitary landfill or passed through
garbage grinders for discharge to a waste disposal plant
"»
Figure 8. Emissions from burning plostic and polyvinyl chloride from electric wire.
If the charge contains more than approximately 30 percent damp
material mixed uniformly with dry combustible material, the pile will
smolder, yielding an undesirably large amount of smoke and a pile
of hot ash for the clean-out operation. In addition, the buildup of a
large pile of charge will cut down the forced air draft through the pile,
which, will further impede the combustion rate. In summary, burner
efficiency decreases and smoke emissions increase with increased
water content in the charge.
Rate of charge. The rate at which refuse can be charged to a
tepee burner to effect a minimum emission of smoke is dependent
mainly on the size of the burner and the amount of available underfire
air. Overcharging a tepee burner, which occurs if the feed system is
not closely regulated, results in increased smoke emission because
of insufficient underfire air. A continuous feed to a tepee burner al-
lows the operator to control both underfire and overfire air to effect
more complete combustion and reduced emission of smoke and fly-ash.
The conveyor is the only feed system capable of a continuous, fairly
uniform rate of charge.
EFFECT OF CLEAN OUT OPERATION
Hardest to control in the tepee refuse burner operation from the
aspect of smoke and fly-ash emissions is the clean-out process since,
under the best of circumstances, there appears to be no suitable way
to remove the ash without some emission of fly-ash.
Although the ash should be cold when removed from the tepee
16 Air Pollution Aspects
-------
burner, unfortunately, in a majority of cases the piles are hot. Figures
9 and 10 show typical hot clean-out operations. The heated air around
and in the ash being moved will rise, carrying with it large amounts of
dust and fly-ash. Figures A-l and A-2, in the Appendix, show examples
of dust collected on sticky paper downwind from a hot clean-out opera-
tion. More dust fell during the 20- and 30- minute sampling of clean-
out than during 5- and 8- hour sampling during regular operation at
approximately the same distances (Figures A-3 through A-6 in Appendix).
Figure 9. Hot clean-out operations of two separate dozer-fed tepee burners.
Of Tepee Burners 17
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Only if the burner has not been overloaded or charged with wet
material and if the forced draft through the pile has been sufficient,
will the ash be cool during the clean-out operation. As it is removed
from the burner, the cold ash may be sprinkled lightly with water to
keep the dust emission to a minimum. Pictures of the clean-out oper-
ation, showing hot ash carried and pushed out (Figures 9 and 10), should
be compared with the picture showing cold ash pushed from the burner
(Figure 11).
Figure 10. Hot clean-out operations of two separate conveyor-fed tepee burners.
18 Air Pollution Aspects
-------
Figure 11. Relatively cold clean-out of conveyor-fed tepee burner.
ECONOMIC AND
OPERATIONAL COMPARISON
There are several disadvantages to operating the dozer-fed
tepee burner. A large dozer operating in a tepee often tears the door
edges with the shovel or blade or rips the forced draft fan ducts from
the burner floor (Figures 5 and 6). After this occurs several times,
the burner owner deems it uneconomical to replace the doors and
grates as is borne out by the fact that 50 percent of the dozer-fed
burners inspected were without forced air and over 70 percent did
not have usable doors (Table 2). Conveyor-fed-burner owners need
not worry about this problem since they can use small, more readily
maneuverable dozers to clean out the burner in the mornings; and
more important, they only use the dozer about 1 hour per day, thus
saving operating cost and wear on the dozer.
Another disadvantage to operating the dozer-fed tepee burner
may be categorized as an industrial hygiene problem. The dozer
operator spends his time driving in and out of the burner, often with-
out tractor cabs, and is exposed to large amounts of dust and heat
(Figure 2). He could easily be injured by exploding pressure cans,
for example, or by stalling his tractor in the flames of the fire.
Of Tepee Burners
19
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The dozer-fed burner is more expensive to operate than the con-
veyor-fed burner as is shown in Table 7. These operating costs do not
include the cost of the land, basic tepee burner, and personnel, which
are assumed to be the same for each method of disposal.
Table 7. COMPARISON OF ESTIMATED COST OF DOZER-
AND CONVEYOR-FED TEPEE BURNER OPERATIONS21
Cost item
Conveyor with 40- by 60-foot
storage building
Large dozer
Small dozer
Total cost per year
Dozer-fed,
dollars/year
13,520 - 19,760C
2,600 3,120d
16,120 - 22,880
Conveyor-fed,
dollars/year
5,000 6,000b
7,800 - 9,360e
12,800 - 15,360
aCost data compiled from participating burner operators.
"Cost includes operating costs plus initial investment ($30,000
to $40,000) depreciated in 10 years.
cBased upon 40 hours per week operation at a cost of $6.50 to
$9.50 per hour. Cost includes operating costs plus initial
investment ($12,000 to $15,000) depreciated in 2 to 3 years.
Based upon 10 hours per week operation at a cost of $5.00 to
$6.00 per hour. Cost includes operating costs plus initial
investment ($6,000 to $8,000) depreciated in 5 years.
eBased upon 30 hours per week operation at a cost of $5.00 to
$6.00 per hour. Cost includes operating costs plus initial
investment ($6,000 to $8,000) depreciated in 5 years.
The high operating cost of the dozer-fed burner is based upon
$6.50 to $9.50 per hour of operation for the large dozers and $5.00 to
$6.00 per hour of operation for the small dozers. The hourly operating
rates are typical for either rented or owned dozers. The cost is high,
for the dozers have a lifetime that will not normally exceed 3 years
because of the extremely large amounts of dust that pass through the
engine.
20
Air Pollution Aspects
-------
The yearly cost of the conveyor, on the other hand, will be only
slightly higher than its yearly depreciation rate since very little money
is needed for maintenance. The lifetime of the conveyor belt should
exceed the life of the tepee burner The conveyor installations can
also feed 25 to 35 percent more material in a working day without
overloading the burner; the resulting more nearly uniform burning
rates in turn reduce air pollution emissions.
LAND USE REQUIREMENTS
In order to determine land-use requirements for tepee-refuse-
burner installations, sticky-paper stands were set up downwind of a
number of burners at various distances to collect dust and fly-ash.
Each stand contained a horizontal sheet of sticky paper and a strip
of sticky paper wrapped around a bottle to show the direction from
which collected dust was coming. 1,2
Review of the dustfall samples and the visual observations taken
in the field, indicates that the nearest boundary should be a minimum
of 1,500 feet from the burner, a distance equivalent to having the
burner located in the center of a square plot of about 200 acres.
Figures A-3 and A-4 in the Appendix, show actual-size pictures of
the fly ash at varying distances up to 1,300 feet from two separate
tepee burners. These samples represent from 5 to 8 hours of fall-
out. The fallout was actually heavier than appears in the pictures
for the smallest particles have been "screened out" of the pictures
by the reproduction method used in printing.
The fly-ash fallout in all samples taken from 0 to 1,290 feet
downwind of the burners was significantly undesirable. To extra-
polate this fly-ash data to a distance from the burner that would in-
sure a desirably low level of fallout is not possible since a desirable
distance would depend upon the affected terrain and the meterological
conditions of the area. In some cases the nearest boundary should
be as much as 2,000 feet from the burner, an area comparable to a
square plot of about 365 acres. The burner site would not be wasted,
for it would be used for sanitary landfill of noncombustibles, ash,
rubber, plastic, and leather products. A 200-acre plot could serve
as a sanitary landfill for approximately 32 years for a population of
50,000, based on a fill depth of 7 feet or as a landfill for tepee-burner
residue for a period of approximately 80 years under the same con-
ditions.
The boundary distance from the burner also depends upon the
land use of the surrounding country. It would be inadvisable to place
the burner within city limits or within areas not zoned agricultural
or heavy industrial.
Figures A-5 and A-6 in the Appendix show the directional dust-
fall obtained by wrapping sticky paper about a jar. In all cases, the
Of Tepee Burners 21
-------
greatest particulate concentration on the paper came from the direction
of the tepee refuse burners.
These pictures of particulate fallout are not representative of
the greatest concentration possible at each respective location since
maximum dust load is a function of maximum wind speed and minimum
dispersion conditions and these pictures only represent the dust concen-
tration that will normally fall downwind when the wind speed is between
10 and 20 miles per hour.
EQUIPMENT AVAILABLE TO CONTROL FLY-ASH
AND SMOKE EMISSIONS
Tepee burner manufacturers have done some research in air
pollution control equipment, but do not now consider such equipment
economically feasible. Some manufacturers estimate an adequate con-
trol system for fly-ash and smoke would cost from $20,000 to $40,000
or as much as the cost of the installed burner. The commercial equip-
ment manufacturers hope that costs can be reduced by design improve-
ments and will probably market equipment in the future.3
One burner operator built his own collection device, an after-
burner followed by water scrubbers, which was observed as part of
the field investigation. It produced very little visible smoke (less
than 30 percent opacity) during 1 hour of operation, during which it
was charged with three packer-loads of municipal refuse. This con-
trol system could probably be reproduced for approximately $20,000
to $30,000.
COMPARISON OF TEPEE REFUSE BURNER
WITH OTHER
MUNICIPAL WASTE DISPOSAL METHODS
From the aspect of air pollution control, the two most effective
methods for disposing of municipal refuse are sanitary landfill and
refractory-type multiple-chamber incinerators. Many smaller com-
munities, however, continue to use tepee burners.
TEPEE INITIAL COST
The initial investment for a tepee refuse burner depends upon
the design capacity of the burner. Typical price ranges for fully
equipped and installed burners are shown in Table 8. Each price
range composites the cost of the burner (including double wall, forced
air system, and double doors), the conveyor system, and the refuse-
receiving building, but does not include the price of a cleanout dozer.
In general, two men can operate a tepee refuse burner.
22 Air Pollution Aspects
-------
The costs for each burner size (Table 8) vary as much as $10,000
and depend upon the shipping costs, installation costs, refuse-receiving
building size, and manufacturer's cost. A typical cost for a tepee burner
equipped with a conveyor, receiving building, and cleanout dozer, serving
a community of 50,000 population is between $90,000 and $100,000.
Table 8. PRICE RANGES OF COMPLETELY INSTALLED CONVEYOR-
FED TEPEE REFUSE BURNERS FOR VARIOUS RATED
CAPACITIES3-
Capacity,
tons per day
45
60
80
100
120
Diameter ,
feet
45.0
52.5
60.0
67.5
75.0
Price range,
dollars13
43
50
60
70
84
- 50,000
- 55,000
- 65,000
- 80,000
- 90,000
aBased on cost data supplied by two major burner manufacturers.
Does not include cost of dozer.
SANITARY LANDFILL
The most practical method of refuse disposal for many medium
and most small communities is the sanitary landfill operation. It has
been estimated that 1 acre will accommodate the refuse of 10,000 people
for 1 year if the recommended procedure of operation is followed and
refuse is compacted to a finished depth of 7 feet. Operating post for
this method ranges between $0.70 and $1.50 per ton of refuse.5 The
initial cost of land could be returned to the investor after the landfill
was completed. In many cases, land value will increase because of
the improvement made by the land-filling operation. Equipment costs
(large dozer plus small equipment) for a sanitary landfill serving a
community of 50,000 people would be about $20,000.
MULTIPLE CHAMBER TYPE
Building a refractory-type multiple-chamber incinerator is often
warranted when the distance from the community for a sanitary land-
fill site is more than 10 to 15 miles, or the cost of hauling is more
than $1.50 per ton. Waste transfer stations, however, allow sanitary
landfills to operate at haul distances greater than 20 miles. The cost
of a refractory-type multiple-chamber incinerator that could serve
Of Tepee Burners 23
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the needs of 100,000 people would range from $375,000 to $1,200,000.6
This range is based on an estimated cost of from $2,500 to $6,000 per
ton of 24-hour burning capacity and the assumption that 1.5 to 2.0 tons
of refuse are produced daily per 1,000 people. For a community of
50,000 people, an incinerator built to handle 150-tons-per-day refuse
would be needed to process a refuse load of 100 tons per day. This
size is based upon a 16-hour working day, which would be more typical
for a smaller community. Thus, the estimated cost for a refractory-
type multiple-chamber incinerator serving 50,000 people (based upon
$5,000 per ton of capacity) is $750,000.
COST COMPARISON
The operating costs, including ash disposal and amortization of
equipment, for a multiple-chamber incinerator would be between $5
and $6 per ton of refuse burned.^ Operating costs per ton of refuse for
a sanitary landfill range from $0.70 to $1.50^; costs for a comparable
size tepee burner range from $0.85 to $1.50. Operating costs for the
tepee burner are based upon data obtained from participating burner
operators plus additional cost added for operating a sanitary landfill
of 30 percent normal capacity to dispose of noncombustibles and ash.
For purposes of comparison, it is assumed that the costs for hauling
refuse to the incinerator or landfill site are $0.50 per ton for multiple-
chamber incinerators, $1.00 per ton for sanitary landfills, and $1.50
per ton for tepee burners. A higher rate is applied for hauling to
tepee burners than to landfill sites because the tepee burners should
be placed outside of a community and a sanitary landfill is often
located within a city limit.
A comparison of typical operating costs (including investment,
depreciation, and labor) and hauling costs for various methods of
waste disposal is shown in Table 9 for a community of 50,000 (4
pounds of waste per day per person or a total of 100 tons of waste
per day).
The very approximate cost data in Table 9 should be used for
general comparisons only since costs may vary considerably from one
geographic location to another. The data in Table 9 do show, however,
that refractory-type multiple-chamber incinerators are considerably
more expensive to operate in smaller communities than either tepee
burners or sanitary landfills. The data also indicate a slightly higher
operating cost for tepee burners than for sanitary landfill operations.
Also, the initial cost of a tepee burner is approximately 5 times higher
than that of a sanitary landfill.
24 Air Pollution Aspects
QPD 801-746-4
-------
Table 9. COMPARISON OF OPERATING COSTS FOR
VARIOUS METHODS OF WASTE DISPOSAL
FOR A COMMUNITY OF 50,000
Operating cost,
dollars per ton of
refuse3-
Hauling cost,
dollars per ton of
refuse
Operating cost,
dollars per yeara
Hauling cost,
dollars per year
Total cost,
dollars per year
Multiple -chamber
incinerator
5.00 - 6.00
0.50
182,500-219,000
18,200
200,700-237,200
Sanitary
landfill
0.70 - 1.50
1.00
25,500-54,700
36,400
61,900-91,100
Tepee
burner
0.85 1.50
1.50
31,000-54,700
54 , 700
85,700-109,400
alncludes amortization of equipment.
ACKNOWLEDGMENTS
The author is grateful for the assistance given by many in-
dividuals and organizations, particularly Greene County, Ohio; the
cities of Highland Park, Illinois; Kokomo and New Castle, Indiana;
Louisville, Kentucky; Flint, Grand Rapids, and Kalamazoo, Michigan;
and Beaver Dam, Beloit, and Marshfield, Wisconsin; the states of
Indiana and Michigan; and private refuse collection companies, in-
cluding America Compressed Steel Corporation, Andy's Waste Dis-
posal Company, Arrow Wrecking Company, Gorton and Jobson,
Kooglers Refuse Collection Company, Hambricki Brothers, and
Spooner Trucking Company, who allowed the Division of Air Pollu-
tion, Public Health Service, to inspect their tepee burners and to
sample for atmospheric pollutants. Their assistance and cooperation
contributed to making the field study successful.
Valuable assistance and information was provided by manu-
facturers of tepee burners. Special acknowledgment is made of the
contribution of Larry E. Crane, Chief, Solid Wastes Training Section,
Training Program, Public Health Service, in the review of this report.
Of Tepee Burners
25
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REFERENCES
1. Gruber, Charles W. and Jutze, George A. The use of sticky paper
in an air pollution monitoring program. JAPCA 7 (2): 115. Aug. 1957.
2. Gruber, Charles W. and Schumann, Charles E. The use of adhesive
coated paper for estimating incinerator emission regulations.
JAPCA 12(8): 376-378. Aug. 1962.
3. Private communication with tepee burner manufacturer. Feb. 24,
1965.
4. Eliot, George F. Garbage is a nasty work, but. . . Suburbia Today.
May 1961.
5. Black, Ralph J. Sanitary Landfills. Pro. Natl. Conf. on Solid
Waste Research. American Public Works Association. Dec. 1963.
6. When should a community consider incineration as a method of
refuse disposal? New Jersey State Department of Health. Public
Health News. Oct. 1960.
7. Private communication with Larry E. Crane, Chief, Solid Wastes
Training Section, Training Program, Public Health Service,
Robert A. Taft Sanitary Engineering Center, Cincinnati, Ohio.
June 22, 1965.
27
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APPENDIX
29
-------
Background sample collected from upwind
burner.
20—minute sample collected 260 feet
downwind of burner.
30-minute sample collected 200 feet
downwind of burner.
Figure A —1. Horizontal sticky paper samples showing particulate collected during clean-out
operation. Hot ash was carried from both burners by dozer scoop. Scale is full
size.
30
Air Pollution Aspects
-------
Area of Paper Facing Tepee Refuse
Burner.
20-minute sample collected 260 feet downwind of burner.
Background sample collected upwind from burner.
30-minute sample collected 200 feet downwind of burner.
Figure A-2. Directional sticky paper unwrapped from bottles showing particulate collected
during the clean-out operation. Hot ash was carried from both burners by dozer
scoop.
Of Tepee Burners
31
-------
Background sample collected 230 feet
upwind of burner.
Sample collected 400 feet downwind of
burner.
Sample collected 600 feet downwind of
burner.
Sample collected 1,000 feet downwind of
burner.
Figure A-3. Horizontal sticky paper samples showing particulate collected in 5 hours at various
distances downwind of conveyor —fed *epee refuse burner. Scale is full size.
32
Air Pollution Aspects
OPO BDl-746-3
-------
Sample collected 220 feet downwind of
burner.
Sample collected 430 feet downwind of
burner.
Sample collected 650 feet downwind of
burner.
Sample collected 1,290 feet downwind
of burner.
Figure A-4. Horizontal sticky paper samples showing particulate collected in 8 hours at various
distances downwind of conveyor—fed tepee refuse burner. Scale is full size.
Of Tepee Burners
33
-------
Area of Paper Facing Tepee Refuse
Burner.
Background sample collected 230 feet upwind of burner.
Sample collected 400 feet downwind of burner.
."•,-•>' :; * .,'
.".*<-"'.'. ^/ >U .,'^fcLJ.\- -V
Sample collected 600 feet downwind of burner.
' '"-:: • .
Sample collected 1,000 feet downwind of burner.
Figure A—5. Directional sticky paper unwrapped from bottles showing particulate collected in 5
hours at various distances downwind of a conveyor—fed tepee refuse burner.
34
Air Pollution Aspects
-------
Area of Paper Facing Tepee Refuse Burner
Background sample collected 75 feet upwind of burner.
Sample collected 175 feet downwind of burner.
Sample collected 700 feet downwind of burner.
Sample collected 1,050 feet downwind of burner.
Figure A—6. Directional sticky paper unwrapped from bottles showing particulate collected in 7
hours at various distances downwind of a dozer-fed tepee refuse burner.
Of Tepee Burners 35
OFO BU1-74C-2
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