Sflffll inClflCRflTORS
evaluation, discussions, and authors' closure
-------
Mr. Achinger, an engineer with the Federal solid
waste management program, presented "An Evaluation
of Seven Incinerators" by W. C. Achinger and L. E.
Daniels at the 1970 National Incinerator Conference;
following the presentation, D. L. Brenchley, P. B.
Hall, F. R. Rehm, C. O. Velzy, W. M. Harrington,
Jr. , and W. R. Niessen discussed the paper. All
this material and the authors' closure are reprinted
by the U.S. Environmental Protection Agency from
the Proceedings (p. 32-64) and from the Discussions
(p. 7-12) of the 1970 National Incinerator Conference,
Cincinnati, May 17-20, 1970, with the permission of
the American Society of Mechanical Engineers, New
York. Mention of a commercial product does not
imply endorsement by the U.S. Government. This is
an environmental protection publication in the_solid
•waste management series (SW-51ts. Ij). '
-------
An Evaluation of Seven Incinerators
W.C. ACHINGER and I.E. DANIELS
ABSTRACT
In an evaluation of seven incinerators that pro-
cess municipal solid waste, data have been gathered
on (1) the quality and quantity of solid waste pro-
cessed, residue, and gasborne particulate emissions,
(2) the quality of the fly ash collected and the waste-
water produced, and (3) the economics involved in
incineration. These data are compared and the study
results summarized. The sampling procedures being
used and the problems encountered during their
evolution are also described.
INTRODUCTION
The 1965 Solid Waste Disposal Act (PL 89-272)
created a federal solid-waste management program to
join air- and water-pollution programs in a national
effort to combat environmental pollution. Realization
of the rapidly increasing types and amounts of solid
waste being generated in this country had prompted
this federal action and the creation of a program, the
Bureau of Solid Waste Management, to lead and co-
ordinate planning and research activities in solid-
waste management on a nationwide level. The broad
objective of the Bureau is to act as a catalyst in the
initiation and utilization of methods of solid-waste
disposal that are effective and economic. Technical
and financial assistance is provided to state and
local governments and interstate agencies for
planning, developing, and conducting solid-waste
management.
Because meaningful data are scarce on incinera-
tion, this program for-testing municipal incinerators
was conceived and initiated by the Bureau's division
of technical operations.
The first phase of this testing program was de-
signed to develop reliable sampling methodology and
accumulate basic data that identify the results of the
incineration process. The intention was to identify
the operating characteristics of the various inciner-
ator designs, not to downgrade or promote any
particular design. This first phase is nearing com-
pletion. The next phase will involve refining and
expanding the sampling methodology developed in
the first phase and continuing the studies of various
incinerator designs.
The sampling procedures now used and the re-
sults of the first seven incinerator studies are given
here. The incinerator designs studied were the
rotary kiln, conical burner (pilot-plant size),
traveling grate, rocking grate, modified reciprocating
grate, and reciprocating grate.
SAMPLING PROCEDURES
At the beginning of this testing program, sampling
procedures for evaluating municipal incinerators
were neither widely published nor accepted. As a
result, the existing sampling procedures have been
considerably modified since the start of this program
in an effort to develop better testing methods. Ad-
ditional modifications are expected as further data
become available.
32
-------
The sampling procedures presently used, reported
in this paper, are designed to obtain information on
(1) the efficiency of the incinerator as a reduction
device, (2) the potential impact of the incinerator
operation on the environment as indicated by the
quality and quantity of the solid, liquid, and gaseous
effluents discharged to the environment, and (3) the
cost of incinerating solid wastes.
Under development are procedures for identifying
the bacteriologic quality of all influents and efflu-
ents and for determining the quantity of gaseous
pollutants, primarily: hydrocarbons, hydrogen chlo-
ride, sulfur oxides, carbon monoxide, and nitrogen
oxides emitted to the atmosphere.
The incinerators are evaluated at their "operating"
capacity (operated in the way the plant would be
operated if it were not being tested) because, at
present, the charging rate on a short-term (hourly)
basis cannot be determined. Evaluating a particular
incinerator at different conditions to determine the
capacity at which it achieved the best overall
operation is no longer done because of the resources
required.
Incoming Solid Waste
Burning Rates
Because design burning rates are sometimes in-
accurate in relation to actual operation at a given
time, it is necessary to determine true burning
rates before waste-reduction efficiencies, particulate-
grain loadings, and other factors can be determined.
Burning rates are determined indirectly by measuring
the charging rate and are most useful if determined
on an hourly basis.
Initially, strain gages mounted on the crane
cables were considered as a means of determining
the hourly charging rate, but this procedure was not
attempted because of anticipated problems as-
sociated with installation. Weighing grapples full
of waste on a platform scale to determine the weight
of an average grapple charge proved unsatisfactory
because it was difficult to keep the cables slack
and at the same time prevent material from falling out
of the grapple during the weighing process.
At present, a weekly charging rate is determined
by emptying the pit before the study, weighing all
materials dumped during the study week, emptying
the pit at the conclusion of the study, and recording
the time it takes to charge the material received
during the study week. This procedure is followed on
a daily basis in those plants that operate less than
24 h/day. When the plant operation permits, suf-
ficient wastes to charge the furnaces for about 8 h is
weighed and set aside. During a testing day, the time
required to charge the material is recorded and used
to determine a daily charging rate. Although neither
of these latter two procedures yield an hourly
charging rate, they do provide data more reliable
than the other procedure.
Composition and Characteristics
To determine the composition of the incoming
waste for the test period, eight grab samples weigh-
ing between 200 and 300 Ib each are manually sorted
into nine categories. The combustible categories in-
clude: (1) food waste, (2) garden waste, (3) paper
products, (4) plastic, rubber, leather, (5) textiles,
and (6) wood. The noncombustible categories include
(7) metals, (8) glass and ceramics, and (9) and ash,
rocks, dirt, etc. The amount in each category is
weighted. Portions of four of the eight grab samples
are collected for laboratory analyses. To obtain a 15-
to 20-lb laboratory sample, a proportionate amount of
material is taken from each of the nine separated
categories. The combustible and noncombustible
materials are placed in separate plastic bags and
sent to the laboratory. Before any other processing
is attempted, the moisture content of the samples is
determined. The combustible portion of all four
samples is then analyzed for heat, volatile (material
driven off at 600°C), and ash contents and for ele-
mental composition (carbon, hydrogen, oxygen,
nitrogen, sulfur, and chlorine).
Size and Number of Samples
During the first study made under this program,
the effect of sample size on the precision of the
data was ascertained. Statistical analysis of the re-
sulting data indicated no difference in the precision
of composition data based upon sample size; the
results were as precise with "small" (i.e., 200- to
300-lb) samples as with "large" (1400- to 1700-lb)
samples if the grab samples were representative
(based upon appearance).
The first study also determined that 12 grab
samples are required to obtain the percentage of any
component with a precision of plus or minus two
percentage points. Because of the manpower and
time required to sort these samples manually, only
eight samples are collected during the course of a
study. This loss of precision is not deemed critical.
33
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A more comprehensive treatment of this statistical
analysis was presented by Carruth and Klee [1].
Distribution of Sampling
The sampling study period of 1 week, which was
shortened to 3 days for Study E, introduced a problem
when trying to characterize the composition of the
solid waste. During Study E, the eight samples for
composition analysis were taken unevenly over the
study period: three samples were taken on the first
day, four on the second, and one sample on the
last. Comparison of the data obtained from the
samples (Table 1) indicates that the wastes de-
livered to the facility on different days had differ-
ent compositions and that sampling to determine
composition must be distributed throughout the week
if the average composition is to be representative
of the material delivered to the facility during any
one week. Analysis of the data from other plants
similarily indicates the necessity of distributing
the sampling over the entire study week.
Moisture Content
In the first two studies, the moisture content of
the combustible fraction of the composition samples
was erratic and unexpectedly low, ranging from 9 to
Table 1
Daily Solid-Waste Composition for Plant E
(Percent by Weight)
Component
Combustibles:
Food waste
Garden waste
Paper products
Plastic, rubber,
leather
Textiles
Wood
Total
Noncombustibles:
Metal
Glass, ceramics
Ash, rock,
and dirt
Total
Mon-
day*
7.2
1.8
57.8
2.7
1.6
0.3
71.4
8.8
14.9
4.9
28.6
Tues-
dayt
14.6
1.9
60.3
2.8
1.7
0.5
81.8
8.0
7.4
2.8
18.2
Wednes-
day t
18.1
0.3
54.1
4.9
2.9
0.3
80.6
10.0
8.2
1.2
19.4
Average^
12.2
1.6
58.7
3.0
1.8
0.4
77.7
8.6
10.3
3.4
22.3
* Average of three samples.
' Average of four samples.
* One sample.
5 Average of all eight
samples.
23 percent. Visual examination of samples indicated
higher moisture contents because the samples were
quite wet. These samples were placed inside 6-gal
plastic cans with the plastic lid sealed with tape,
and analysis of the samples occurred some time
after the samples were taken. When this apparent
loss of moisture during transport and storage became
evident, extra precautions were taken on subsequent
studies to seal the samples securely. Samples are
now placed inside two independently knotted plastic
bags. Moisture contents of the combustible portions
of samples sealed in this manner have ranged from
22 to 43 percent.
In all of these studies, the moisture content of
the noncombustible fraction of the solid-waste
samples has been assumed to be zero, since moisture
determinations were not practical with the equipment
available. Grinding the noncombustible fraction to
homogenize the sample for moisture analysis was
considered impractical because of the abrasive
properties of these materials. Arrangements have
been made to have the moisture content of the
entire combustible and noncombustible laboratory
samples determined in larger capacity ovens in
future studies.
Residue and Fly Ash
All the residue accumulated during the study
period is weighed, and the information is used to
determine reduction efficiencies, as is discussed
later in the section on study results.
To determine the quality of the residue, five
grab samples each weighing approximately 50 Ib are
collected during the study period. A statistical
analysis was not made of the number and size of the
residue samples required because, at a given
facility, the composition of the residue does not vary
as much as that of the solid waste. Four of the five
samples are manually sorted into four categories:
(1) metals (2) rocks, glass, and ceramics, (3) un-
burned combustibles, and (4) fines (unidentifiable
material passing through a 0.5-in. sieve).
The fifth sample is returned to the laboratory
for determination of moisture content. The fines and
the unburned combustibles of the other four samples
are placed into two independently sealed plastic
bags and returned for laboratory analyses similar to
that of the incoming solid waste.
Where possible, a 2- to 10-lb sample of fly ash is
collected from the air-pollution-control device. This
is returned to the laboratory to determine the mois-
ture, heat, ash, and volatile contents.
34
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A material balance of the metals from the solid
waste and from the residue may not be calculated
because a considerable portion of the fines in the
residue contain metal that is not removed during the
current separation procedure. In one study, for ex-
ample, the plant received 2300 tons of solid waste
that contained 8.5 percent (195.5 tons) metal. The
660 tons of residue weighed contained 16.8 percent
(110.9 tons) metal. From these data, it would seem
that 84.6 tons of metal disappeared during incinera-
tion. In preparing the laboratory sample of the fines
for analysis, however, 13.7 percent of the fines were
removed with a magnet. This magnetic material ac-
counts for another 71.8 tons of ferrous metal in the
residue to reduce the apparent loss of metal to 12.8
tons, which is within the accuracy of our sampling
procedures. The residue separation procedures are
being modified to include removal of ferrous metals
from the fine category.
Liquid Effluents
Each wastewater source is sampled to determine
pertinent physical and chemical characteristics. The
major sources sampled are the incoming water,
scrubber water, residue quench water, and plant ef-
fluent. Two 500-ml grab samples are collected from
each source during each stack test and combined.
The temperature and pH of all samples are measured
immediately after collection. After the samples are
returned to the laboratory, they are analyzed for
alkalinity, chlorides, hardness, sulfates, phosphates,
conductivity, and solids [2].
Stack Effluents
Particulate Emissions
The sampling train (Fig. 1) and methods developed
by the National Air Pollution Control Administration
(NAPCA) are used for measuring particulates emitted
from the stack [3]. The major elements of this
sampling train are the (1) stainless-steel button-hook
probe tip, (2) glass-lined or all metal probe, (3)
cyclone and collection flask, (4) 2.5-in. glass-fiber
filter, (5) electrically heated enclosed box, (6) series
of four modified Greenburg-Smith impingers (the first
impinger has the tip replaced with a 0.5-in i.d. glass
tube and is filled with 100 ml distilled water;-the
second impinger (unmodified) is filled with 100 ml
distilled water; the third impinger is modified like
the first and is left dry; and the fourth impinger is
also modified like the first and contains about 175
g of dry silica gel, (7) box containing an ice bath,
(8) dial thermometer, (9) check valve, (10) flexible
vacuum tubing, (11) vacuum gauge, (12) needle
valve, (13) leakless vacuum pump, (14) bypass
valve, (15) 1 ft3/r dry gas meter, (16) calibrated
orifice, (17) inclined-vertical manometer, and (18)
Type S pitot tube.
Gas Composition
The effluent gases are sampled and analyzed for
moisture, carbon dioxide, carbon monoxide, and
oxygen. To determine the moisture content, water
vapor is condensed in the impingers of the particu-
late sampling train, and then the gases are passed
'5 13
Fig. 1 Particulate Sampling Train
35
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through silica gel to dry. The condensate in the im-
pingers and the weight gain in the silica gel
(assumed to be moisture adsorption) are measured to
indicate the moisture content of the stack gases. To
determine the carbon dioxide, carbon monoxide, and
oxygen concentration, integrated gas samples are
collected in a flexible bag sampler during each stack
test and then analyzed with the use of an Orsat
analyzer. To check the carbon dioxide data, a series
of instantaneous grab samples are also taken during
each stack test and analyzed with the use of a
manual wet-chemistry carbon-dioxide indicator.
Probe Corrosion
Some municipal incinerators have large-diameter
stacks, sometimes with double walls, that require the
use of long probes when sampling the effluent gases.
Because of handling difficulties and breakage, it is
impractical to use glass-lined probes over 7 ft in
length. In these situations, unlined, unheated metal
probes have been used.
Type 304 stainless steel was initially selected
as the probe material when the use of all-metal
probes was necessary. These probes were used in
two studies spaced about 5 months apart. Some
visible evidence of corrosion was noted during the
first study. Because of the natural reddish-brown
color of the particulate collected on the filter,
corrosion could not be established definitely without
a thorough laboratory analysis, which did not seem
justified at the time. Reddish-brown material was
also noted in the probe washings collected during the
second study. Since the natural color of the material
collected on the filters was black, oxidation of the
probe metal probably occurred. Visual inspection of
the inside walls of the probes revealed this pos-
sibility. The reddish-brown residue remaining after
evaporation of the acetone wash in this study was
qualitatively analyzed for iron and indicated a high
iron concentration, but the particulate material col-
lected on the filter showed only a faint trace of iron.
This indicates the iron came from the probe rather
than the incinerator. Even though the iron from the
probe adds some to the total particulate collected,
visual inspection did not indicate it to be a
significant amount.
The corrosion is caused by condensation occur-
ing in the probe. Because the metal probes were not
heated, considerable amounts of liquid (up to 135 ml)
have condensed in the all-metal probe and cyclone
through which the gases pass before entering the
particulate filter (Fig. 1). The gases cool sufficient-
ly in the length of the probe to condense even though
they enter the probe at approximately 500 to 600°F.
It is suspected that acidic gases, particularly hy-
drogen chloride, are absorbed in this condensed
water and create a very corrosive solution. In sub-
sequent studies, the pH of the water removed from
the impingerswas measured and found to vary be-
tween 2.5 and 3.5.
Two alternatives were considered for correcting
the corrosion problem in metal probes. The probes
could be heated, or more corrosion-resistant
materials could be used. Because of the problems
involved in shielding the heating wire or tape, it
was decided to try more resistant probe materials.
Two alloys, Incoloy 825 (approximately 40 percent
nickel, 30 percent iron, and 20 percent chromium)
and Monel 400 (approximately 65 percent nickel, 30
percent copper, and 1 percent iron), were investigated
because of their reported resistance to corrosion by
acidic gases. The two different materials were used
simultaneously in one study. The Incoloy 825 probes
seemed to be more resistant to corrosion; the wash-
ings were generally clear, and inspection of the
inside walls showed no indication of corrosion. The
washings from the Monel probes were yellow and
contained greenish material that indicated the
presence of copper compounds. The inside walls
showed visible signs of corrosion. Although the
Incoloy 825 seems promising in its ability to resist
corrosion by incinerator stack gases, it is too early
to make a positive conclusion. The use of heated
glass-lined probes is recommended whenever
possible.
Fi Iter Plugging
Filter plugging due to particulate buildup or to
moisture condensing on the filter has also been a
problem in testing. Rather than attempting to
develop a larger filter assembly that would require
extensive modification of the sample collection box,
the sampling train is merely shut down for a few
minutes while the filter assembly is changed. In
some cases, as many as four filter changes were
necessary to complete a test. This method of
operation is rapid and has proven satisfactory during
the studies.
36
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chemotic for Incinerator
]
A PRIMARY CHAMBER ||\.
K\ Is
STACK -~
A
INDUCED-
DRAFT FAN
J SECONDARY SCRUBBING
CHAMBER 1 AREA
— - 1 A
-
&K /
^-^L /
) QUENCHING SYSTEM | • >| LANDFILL
t
[
^
3
/
STORAGE PIT
LAGOON NO 2
Fig. A-2 Flow Diagram for Incinerator A
FLOW SAMPLING POINT
SOLID WASTE. RESIDUE
AND FLY ASH
PROCESS WATER -
GASES AND PARTICIPATES ---
-CHARGING
HOPPER
Fig. A-3 Schematic for Incinerator B
37
-------
I ATMOSPHERE [--jj FURNACE
jri
STORAGE PIT
FLOW SAMPLING POINT
fl
SOLID WASTE
SOLID WASTE. RESIDUE.
AND FLY ASH
PROCESS WATER -
GASES AND PARTICULATES ---
Fig. A-4 Flow Diagram for Incinerator B
^PRECIPITATCR
FAN AND STACK
ELECTROSTATIC PRECIPITATOR
WATER SCRUBBER,
FAN. AND STACK
CONICAL BURNER
Fig. A-5 Plan View for Incinerator C
SECTION A-A
i i ii T i T r /. / / T
ff/KWfffrjXWsss* \ \ ^ T*^* 7 / ' •——T7 / 7
Fig. A-6 Underfi re-Ai r System for Incinerator C
38
-------
Cost Data
The objective of collecting cost data is to
determine the true costs at each plant studied, which
includes costs for residue disposal, facility amortiz-
ation, bond interest, site improvement, etc. In ad-
dition to obtaining overall operating and capital
costs, the operating costs are divided into solid-
waste receiving, volume-reduction, and effluent-
treatment "cost centers."
The cost data are obtained by checking all cost
records kept by the plant and any administrative
group keeping pertinent records. In addition, to
verify and apply the cost data to the cost accounting
procedure correctly, discussions were held with the
personnel who maintain cost records. This cost ac-
counting procedure has been described by Zausner
[4], and the computerized cost-analysis technique
used in the studies has been described by Zausner
and Helms [5].
The cost analysis is presently being expanded to
include a capital cost breakdown according to cost
centers. Unfortunately, capital cost information,
when available, is not easily allocated to the cost
centers because the data are not available in a form
that lends itself to the cost-center concept.
AFTERBURNER
SAMPLING PORTS
DUCTWORK TO
PRECIPITATOR
WATER SCRUBBER
GUILLOTINE DAMPERS
Fig. A-7 Water Scrubber and Afterburner Ductwork for
Incinerator C
SAMPLING PORTS
X
DUCTWORK TO WATER SCRUBBER
AND FROM INCINERATOR
Fig. A-8 Electrostatic-Precipitator Ductwork for
Incinerator C
39
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In addition to breaking down capital costs ac-
cording to cost centers, future studies under this
program will include cost analysis according to sub-
systems within each cost center. For the "Receiving
and Handling" cost center, costs are assigned to the
scales, pit and tipping area, and the crane and
charging floor; for the "Volume Reduction" cost
center, to the furnace enclosure, grates, combustion-
air systems, and instrumentation; and for the
"Effluent Handling and Treatment" cost center, to
residue, wastewater, and gas-treatment systems.
STUDY RESULTS
Facility Descriptions
Incinerator A was built in 1966 with a design
capacity of 300 tons/day. Each furnace contains a
modified reciprocating grate and a stationary grate.
A wetted-column water scrubber is used for air-
pollution control. Incinerator B was built in 1966
with a design capacity of 300 tons/day. Each furnace
ATMOSPHERE
* -r,,r,<-r,, ,,-,-,,-
1 ,., .T^'r'^r^1",, *
AF
A
•b i
COMBUSTION
CHAMBER
SCREW
CONVEYOR
1
HOPPER
I
SCALE
f
WASTE
TRAILER
t
MUNICIPAL
COLLECTION
SYSTEM
TEP8UPNER ' n '
>*"\ !
1 / M '
\/ 7- SCWRUTBEBRER -^1
-->. DUCT ,,''/" T
SYSTEM \^ j/ 1
\ 7^s ELECTROSTATIC '
\ r PRECIPITATOR ~*
V
SETTLING
BASIN
WATER
COURSE
SOURCE FLOW SAMPLING POINT
SOLID WASTE AND RESIDUE > •
PROCESS WATER ^— *
GASES AND P ARTICULATES ^> ^
Fig. A-9 Flow Diagram for Incinerator C
PRIMARY COMBUSTION CHAMBER
TRAVELING GRATES
UNDERFIRE AIR
PLENUM CHAMBERS
GUILLOTINE
DAMPER\
SECONDARY
COMBUSTION
CHAMBER
\
FLOODED BAFFLE
WALLS
Fig. A-10 Schematic for Incinerator D
40
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contains three sections of rocking grates. The air-
pollution-control system is a flooded, baffle-wall
water scrubber. Incinerator C, built in 1967, is a
pilot-plant conical burner with a design capacity of
1000 Ib/h. A centrifugal water scrubber, an after-
burner, an electrostatic precipitator, or some com-
bination thereof is used for air-pollution control.
Incinerator D was built in 1965 with a design capac-
ity of 500 tons/day. Each furnace contains two
sections of traveling grates, and a flooded, baffle-
wall water scrubber is used for air-pollution control.
Incinerators E and F are rotary kilns built in 1963
with design capacities of 500 and 600 tons/day,
respectively. Each furnace contains three sections
of reciprocating grates followed by a rotary kiln.
Air-pollution control is achieved through a baffle-
wall and water-spray system. Incinerator G was
built in 1967 with a design capacity of 400 tons/day.
Each furnace contains four sections of reciprocating
grates. A multitube dry cyclone following a wet-
baffle wall is used for air-pollution control.
A more detailed summary of the physical charac-
teristics of each incinerator studied is presented in
the Appendix.
Heat Release and Burning Rates
The design burning rate per unit area of grate and
the heat release rate per unit volume (Table 2) for
each incinerator were calculated by using the design
capacity of the plant and waste averaging 5000 Btu/
Ib. The actual burning and heat-release rates were
ATMOSPHERE
!
r, -
! MUNICIPAL WATER SUPPLY
i
1
— > FURNACE 1 •
A
SETTLING BASIN
1
:
> QUENCHING SYSTEM
=**
1
1
LANDFILL
STORAGE PIT
SCALE
SOLID WASTE
SAMPLING POINT
SOLID WASTE. RESIDUE. ,.
AND FLY ASH •'
PROCESS WATER >
GASES AND PARTICIPATES >
Fig. A-ll Flow Diagram for Incinerator D
CRANE
1
— \
\
4
-f- HOPPER
j — GAS BYPASS — .v
^2_^~1 1
STACK— -
(AJ DRYING GRATES
(g) IGNITION GRATE
(£) UNDERFIRE AIR PLENUM
(5) OVERFIRE AIR DUCTS
GUILLOTINE
DAMPERS
QUENCH
Fig. A-12 Schematic for Incinerators E and F
41
-------
SOLID WASTE AND RESIDUE
PROCESS WATER
GASES AND PARTICIPATES ^
Fig. A-13 Flow Diagram for Incinerator E
Flg. A-14 Flow Diagram for Incinerator F
42
-------
calculated from the charging rate of the plant and the
heat content of the solid waste as measured during
the study. For the conical burner, the area of the
base of the burner was used to calculate the grate
burning rate. For the rotary kilns, the grate burning
rate was calculated with the use of the surface area
of a 2-ft bed depth in the kiln.
Solid Waste
Composition
The solid waste (Table 3) received by the incin-
erators during the studies was composed generally of
79 percent combustibles and 21 percent non-
combustibles.
QUENCH TANKS
Fig. A-15 Schematic for Incinerator G
SOURCE
SAMP LING POINT
SOLID WASTE AND RESIDUE
PROCESS WATER
BASES AND PARTI CULATES
Fig. A-16 Flow Diagram for Incinerator G
43
-------
Proximate Analyses
The low combustible content of the waste re-
ceived by Incinerators C and G is reflected in a
lower volatile and heat content of the waste (Table 4).
Residue
Composition
The residue composition (Table 5) is expressed
on a percent by weight "as-sampled" basis. The
fines are defined as the unidentifiable materials
passing through a 0.5-in. wire-mesh screen. The
unburned combustibles are those visually identifiable
Table 2
Heat-Release and Burning Rates
Capacity
Incinerator (tons/day)
A
B
C
D
E
F
G
Design
300
300
1000*
500
500
600
400
Actual*
281
308
1444*
(t)
660
645
482
Burning Rate Per
Unit Area of Grate
(Ib/ftVh)
Design
45
52
3
(t)
45
47
51
Actual
42
53
5
(*)
59
50
62
Rate of Heat Release
Per Unit Volume
(Btu/ftVh)
Primary
Design
23,000
28,600
-
M
23,300
21,900
23,600
Chamber
Actual
19,000
25,300
—
(0
31,000
26,000
22,000
Total Furnace
Design
14,300
13,800
2,400
(1)
13,900
14,400
14,400
Actual
11,800
12,300
2,600
(*)
18,600
17,000
13,400
* See discussion of burning rates under the section on the sampling of incoming solid
waste.
T Ib/h.
* Information not available.
Table 3
Solid-Waste Composition
(Percent by Weight)
Component
Combustibles:
Food waste
Garden waste
Paper products
Plastic, rubber
leather
Textiles
Wood
Total
Noncombustibles:
Metal
Glass, ceramics
Ash, rock, dirt
Total
Incinerator
A
7.4
3.4
62.5
2.8
2.4
2.4
80.9
9.0
4.2
5.9
19.1
B
6
8
58
3
3
1
80
8
8
3
19
.1
.4
.0
.3
.1
.4
.3
.2
.1
.4
.7
C
20.
11.
30.
3.
5.
1.
71.
6.
10.
11.
28.
3
1
2
1
2
7
6
8
5
1
4
D
8.
0.
60.
5.
2.
5.
82.
9.
3.
4.
17.
5
5
4
4
4
4
6
0
5
9
4
E
12.2
1.6
58.7
3.0
1.8
0.4
77.7
8.6
10.3
3.4
22.3
F
18
0
60
2
1
2
85
8
5
0
14
.3
.6
.6
.1
.8
.3
.7
.5
.4
.4
.3
G
11.0
9.8
44.9
3.5
3.2
3.1
75.5
8.1
9.5
6.9
24.5
Table 4
Solid-Waste Analyses
Incin-
erator
A
B
C
D
E
F
G
Moisture,
As
Sampled
20.0*
20.0*
26.5
20.7
20.2
21.0
28.2
Heat,
As
Sampled
(Btu/lb)
4410
4320
3770
4520
5030
5530
3870
Ash,
Dry,
Basis
34.2
31.8
47. 1
35.6
29.9
22.7
42.3
Volatiles,
Dry
Basis
65.8
68.2
52.9
64.4
70.1
77.3
57.7
Density,
As
Sampled
(lb/yd3)
(')
(T>
(T)
(T)
200
140
230
*Assumed.
*No measurement made.
44
-------
combustible materials that pass through the inciner-
ator without being burned. The unburned com-
bustibles describe the visual appearance of the
residue rather than the combustible content of the
residue. The volatiles and heat content are more
reliable indicators of combustible content. As stated
previously, the fines also contain ferrous and non-
ferrous metals that are not determined during the
separation procedure.
Incinerators E and F, rotary kilns, probably pro-
duced a higher percentage of fines than the other
incinerators (74.5 and 79.4 percent, respectively)
because the tumbling action of the kiln reduced the
size of glass and rocks. The larger percent produced
by Incinerator F, although not great, could be be-
cause its kiln is longer than that of Incinerator E,
30 ft compared with 23.
Table 5
Residue Composition
(Percent by Weight)
Component
Fines
Unburned
combustibles
Metal
Glass, rock
Incinerator
A*
44.9
(f)
23.9
31.2
B
52.5
14.6
32.9
C
38
1
13
46
*
.9
.3
.0
.8
D
36.
35.
14.
13.
4
8
5
3
D
74.
0.
21.
4.
5
1
4
0
F
79.
0.
16.
3.
4
7
8
1
G
52.6
1.1
20.0
26.3
* Dry samples.
t Unburned combustibles included with fines.
Table 6
Residue Analyses
Incin-
erator
A
B
C
D*
E
F
G
Moisture,
As
Sampled
(%)
15.0*
24.5
0.3
-
21.8
24.8
10.5
Heat,
Dry
Basis
(Btu/lb)
170
200
180
-
520
940
70
Ash,
Dry,
Basis
(%)
97.4
98.4
98.0
-
97.0
92.7
99.4
Volatiles,
Dry
Basis
(%)
2.6
2.0
2.0
-
3.6
7.3
0.6
Density,
As
Sampled
(lb/yd3)
(T)
(t)
(T)
-
1490
1620
1600
* Assumed.
f No measurement made.
* No laboratory analysis performed.
Incinerators C and D, a conical burner and a
traveling grate, produced the lowest percentage of
fines, 38.9 and 36.4 percent, respectively. The
residue from Incinerator C fused into a slag that
minimized the quantity of fines.
The residue from Plant D contained 35.8 percent
unburned combustibles. The facility was overloaded
during the study week because the refractories in one
furnace had collapsed. Although the actual burning
rate could not be determined because the solid waste
was stockpiled during the time and no reliable
estimate could be made of the quantities burned,
waste was being processed as fast as possible. The
obviously overloaded furnace and the lack of
agitation on the traveling grate contributed to the
high percentage of unburned combustibles.
Proximate Analyses
The proximate analyses (Table 6) of the residue
indicate the composition of the residue. The residue
from the conical burner, Plant C, was air cooled but
not water quenched; thus, the moisture content is
quite low. The samples from Plants B, E, F, and G
were taken from the drag conveyor. No explanation
can be given for the low value at Plant G.
The moisture content, which is an important
consideration when determining incinerator ef-
ficiencies, can change drastically depending upon
where the sample is taken. For composition analysis,
the best sampling location is the residue conveyor.
This, however, is the poorest sampling location for
the moisture determination needed to calculate in-
cinerator efficiencies, since the moisture content of
the residue is the highest when leaving the conveyor
and the lowest when the residue truck is weighed.
For accurate calculation of incinerator efficiency,
the moisture content of the residue when it is weigh-
ed must be known. Since the residue samples in
Studies B, E, F, and G were taken from the residue
conveyor, the moisture content of the samples is
higher than it would be if the samples had been
taken from the residue truck when it was weighed.
In the efficiency calculations, however, the
moisture contents of the samples as collected
were used. This assumption increases the calcu-
lated efficiencies. If the moisture content of the
residue at the time the residue truck was weighed
were 10 percent lower (14.5 instead of 24.5), the
weight reduction efficiency would be reduced by
about 4 percentage points, the volatile reduction by
about 0.2 percentage points, and the reduction in
heat content by about 0.4 percentage points.
45
-------
Fly Ash
Fly-ash samples could be obtained from only four
of the plants studied. The variation in the proximate
analysis (Table 7) was probably because of dif-
ferent air-pollution-control devices. The electro-
static precipitator (Plant C) collected fly ash with
the highest volatile content, multitube cyclone
(Plant G) with the lowest, and the water scrubbers
midway between that collected by the other units.
The difference between the water scrubbers and the
cyclone may be explained by the better burnout
achieved by Plant G (cyclones) where both the
residue and fly ash had low volatile and heat con-
tents. Since the electrostatic precipitator is con-
sidered a "high-efficiency" control device (collects
smaller particles than less efficient devices) and the
water scrubbers and multitube cyclone are con-
sidered "low-efficiency" devices, the combustible
portion (indicated by the percent volatiles) of the fly
ash would probably be smaller in particle size than
the noncombustible portion of the fly ash.
Wastewater
The incoming water, scrubber water, quench
water, and plant effluent after treatment were
sampled to determine their characteristics. The
Table 7
Fly-Ash Analyses
Moisture, Heat, Volatiles, Ash,
Incinerator, Type As Dry Dry Dry
of Air-Pollution- Sampled Basis Basis Basis
Control Equipment (%) (Btu/lb) (%) (%)
A, wetted-column
water
scrubber 64.9 180
B, flooded baffle-
wall water
scrubber (*) 1290
14.0
86.0
scrubber and quench waters from Incinerator A were
not mixed and flowed to separate lagoons. The
scrubber and quench waters from Incinerator B were
not combined, but both were recycled individually
and, after a week, discharged to the city sewers.
The process waters from Incinerators D, E, F, and G
were combined in the quench tank, treated in a
settling basin, grit chamber, or lagoon, and were
discharged. In these incinerators, the source labeled
quench water (Table 8) is actually a mixture of the
scrubber and quench water.
The temperature and pH were determined at the
plant site, and the remaining analyses were made
after the samples were returned to the laboratory.
From the analysis of the process waters (Table 8),
some general conclusions can be made about the
characteristics of the water from a given source.
Scrubber Water
Scrubber water was generally acidic. The total
solids concentration varied from about 500 to 7000
mg/1 with about 80 to 85 percent being dissolved
solids. The chloride, hardness, sulfate, and phos-
phate concentrations of the incoming water were
significantly increased after passing through the
scrubber.
Quench Water pH
The quench waters from Incinerators A and B
were alkaline because the scrubber water was not
added to the quench water. Although the spray water
used to cool the flue gases and the water used to
carry the fly ash to the quench tank in Incinerator G
were added to the quench tank, the volumes were-not
large enough to reduce the pH of the quench water,
and it remained alkaline. The scrubber water in
Incinerators E and F was acidic, but combining it
with the quench water helped raise the pH of the
combined waters.
13.9 86.1 Quench Water Solids
C-l, centrifugal
water
scrubber
G, multitube
cyclones
(*)
C-3, electrostatic
precipitator 52.4
0.3
(*)
3400
440
16.4
27.5
4.2
83.6
72.5
* No measurement made.
The quench water from each incinerator had a
high concentration of total solids. The quench water
from Incinerators A, E, and F, however, contained
approximately 60 percent suspended solids, whereas
the quench water from Incinerators B, D, and G con-
tained approximately 25 percent suspended solids.
There is no explanation for this anomaly.
At Incinerator E, a grit chamber achieved a 90
percent reduction in suspended solids concentration;
46
-------
Toble'8
Wastewater Analyses
Incinerator,
Sample Source
A, quench water
A, scrubber
water
B, quench water
B, scrubber
water
C-l, scrubber
water
C-l, settling-
tank water
C-2, scrubber
water
C-2, settling-
tank water
C-3, precipitator
drain water
C-3, settling-
tank water
D, quench water
D, scrubber
water
E, tap water
E, quench water
E, scrubber
water
E, final
effluent water
F, tap water
F, quench water
F, scrubber
water
Tempera-
pH ture (°F)
8.4-11.2 (t)
3.8-4.2 (f)
11.2-11.5 110
4.8-6.5* 165
2.6 (t)
2.6 (f)
2.6-3.4 (r)
2.4-3.6 (f)
3.6-4.0 (t)
3.4-4.2 (f)
5.9-7.1 (t)
1.8-7.6 C)
8.4 (t)
3.9-7.0 120
2.5-3.0 150
4.5-6.9 110
5.9 (f)
5.4-7.1 68
3.0-5.0 82
Suspended
Solids
(mg/1)
1860
1350
1300
320
110
120
90
180
1720
600
460
280
0
900
90
85
0
760
90
Dissolved
Solids
(mg/1)
1280
5820
2660
8840
540
500
450
480
7360
1300
2040
1740
56
590
750
570
75
360
520
Total
Solids
(mg/1)
3140
7170
3960
9160
650
620
540
660
9080
1900
2500
2020
56
1490
840
655
75
1120
610
Alkalinity
(mg/1
CaCO3)
120
1.0
720
23
0
0
0
0
0
0
600
80
100
240
0
110
74
140
29
Chlorides
(mg/1)
420
2300
680
3540
270
280
200
230
3200
470
360
700
7
200
300
200
4.0
98
180
Hardness
(mg/1
CaCO3)
460
3430
980
2630
110
110
150
120
1890
400
550
900
33
290
260
270
46
180
190
Sulfates Phosphates
(mg/1) (mg/1)
230
720
120
1250
110
80
100
70
460
100
280
220
1.0
25
28
33
5.0
45
24
0.5
51
38
13
4.4
4.1
4.1
6.0
54
24
21
19
0.1
21
13
4.9
0.2
14
8.8
Conductivity
(^mhos/cm)
3000
7100
-
-
1800
970
1000
850
6000
1600
2020
3640
46
810
1360
750
46
530
630
-------
Table 8 (Cont'd)
-Cx
-------
at F and G, lagoons achieved a 24 and 90 percent
reduction, respectively. The poor achievement at F
(24 percent) was due to the fact that the lagoon was
filled with solids. These systems also reduced the
alkalinity and phosphate concentrations; the chloride
and hardness concentrations remained about the
same.
These data indicate the necessity of treating in-
cinerator wastewater before its discharge to a
watercourse.
Particulate Emissions
The particulate-emission data (Table 9) are the
average of the data collected during each study and
reflect the design, operation, and air-pollution-
control.equipment of the particular plant at the time
of the study. All calculations are based upon
standard conditions of 29.92 in. mercury and 70°F.
Particulate emissions are expressed in the most
commonly used units: grains per standard cubic
foot (gr/st ft3) at 12 percent carbon dioxide, lb/1000
Ib at 50 percent excess air, Ib/h, and Ib/ton of waste
charged. No correction factor was used to account for
any absorption of carbon dioxide that might have
occurred in the water scrubbers when the grain load-
ings were adjusted to 12 percent carbon dioxide.
Comparison with Emission Standards
The particulate emission data, expressed in gr/st
ft3 at 12 percent carbon dioxide, are compared with
the emission standards for Los Angeles County Air
Pollution Control District, federal installations, and
the State of New Jersey (Fig. 2) [6]. The data are
also compared with ASME weight concentration
standards (Fig. 3) [7]. The particulate-emission
level of the revised ASME Model Smoke Ordinance
varies since the ordinance allows smaller installa-
tions to emit more materials than larger installations.
A comparison with New York State and with New
York City weight-rate emission standards is illus-
trated (Fig. 4). These standards also vary with the
size of the incinerator. The incinerators studied meet
a standard if the bar chart for the incinerator falls
below the line depicting the level of the standard.
As can be seen from these comparisons, these in-
cinerators with their existing air-pollution-control
equipment fail to meet all but the weakest standards.
Because the trend in air-pollution control is toward
more stringent standards, more efficient air-pollution-
control equipment will have to be applied to in-
cinerators if they are to meet air-pollution-control
regulations.
.— LOS ANGELES AIR POLLUTION CONTROL DISTRICT
FEDERAL INSTALLATIONS
NEW JERSEY
§ 075 -
B C-l C-l C-3 D
INCINERATOR
Fig. 2 Particulate-Emission Data Compared with Grain-
Loading Emission Standards for Los Angeles
County Air Pollution Control District, Federal
Installations, and State of New Jersey
3.0
2.5
2.0
1.5
1 0
0.5
0.0
ORDINANCE STANDARD
ORDINANCE STANDARD VARIES
WITH CAPACITY OF INSTALLATION)
Fl
X
f
• •%£•
1
i
I
\
^
%
^
I
~
^,
^
\
//,
Y
1
INCINERATOR
Fig. 3 Particulate-Emission Data Compared with ASME
Weight-Concentration Emission Standards
49
-------
Particulate Catch after the Filter
The recommended NAPCA sampling train and
analytical procedures are used in our studies.
NAPCA defines particulates as anything except un-
combined water that would be a solid or liquid at
standard conditions (70°F and 29.92 in. mercury).
This definition focuses attention.upon the material
collected in the sampling train after the filter,
which can be a significant portion of the total
particulate catch (Table 10). To pass through the
filter (MSA Type 1106 HB high-efficiency filter),
this material must be submicron or in a gaseous
state that condenses to a liquid or solid once it
enters the cold region (70 to 100°F) in the impingers.
To truly come within this definition of particulates,
this material must not be formed by a reaction with
.other materials that would remain a gas if emitted to
the atmosphere. Air-pollution experts disagree
whether or not the material collected after the filter
should be reported as particulates. Analyses of the
material to identify it and its origin are needed to
determine whether it should be reported as
particulates.
Particulates caught after the filter include (1)
residue left after evaporation of the acetone used to
rinse the sampling train after the filter and before the
impinger that contains the silica gel, (2) residue left
after evaporation of the chloroform and ether used to
375
275
NEW YORK STATE [EXISTING UNITS)
NEW YORK STATE (NEW UNITS)
NEW YORK CITY
INCINERATOR
Fig. 4 Parti culate-Emi ssion Data Compared with New
York State and New York City Weight-Rate Emis-
sion Standards
Table 10
Summary of Particulate-Catch Data
Incinerator
Particulate Catch after
Filter as Percent of
Total Particulates
Impinger-Water Particulates
as Percent of Particulate
Catch after Filter
Impinger-Water Particulates
as Percent of Total
Particulate Catch
A
B
C*
c-it
C-2f
C-3t
D
E
F
G
Average
High
23.7
19.0
45.8
34.5
54.4
75.6
18.7
35.4
28.2
31.6
-
Low
7.7
0.7
12.7
20.7
44.3
70.8
4.0
27.6
16.4
18.2
-
Average
16.
13.
31.
28.
47.
73.
11.
31.
21.
26.
30.
1
6
0
1
7
3
7
1
1
4
0
High
93.7
81.2
69.9
83.3
80.9
86.7
92.8
93.8
88.9
43.3
-
Low
35.8
69.7
26.2
73.3
74.4
45.6
47.3
90.7
77.1
17.4
-
Average
68
74
45
81
77
72
78
92
83
31
70
.3
.1
.5
.0
.4
.0
.0
.2
.1
.5
.3
High
16.4
14.9
20.6
25.2
44.4
64.0
15.2
34.1
25.0
10.6
-
Low
5.5
4.8
6.7
17.2
33.0
34.7
1.9
25.7
13.2
5.4
-
Average
10.4
10.6
13.6
22.0
37.0
52.9
9.5
28.9
18.0
8.0
21.1
* Sample taken at inlet to air pollution control equipment.
T Sample taken at outlet from air pollution control equipment.
50
-------
extract organic materials from the impinger water
wash, and (3) residue after evaporation of the im-
pinger water wash (Fig. 5).
In these studies, this material averaged 30.0 per-
cent of the total particulate caught. In one study
(C-3), however, it amounted to 73.3 percent. The
four parts of the study at Incinerator C represent
data taken at the inlet to the air-pollution-control
systems (C), the outlet of the water scrubber (C^,
the outlet of the water acrubber with the afterburner
in operation (C2), and the outlet of the electrostatic
precipitator (C3). The percent of material caught
after the filter increased with collector efficiency,
which indicates the amount caught depends on the
type of air-pollution-control device. Undoubtedly
other factors such as the operation, dust loading,
and particle size of the dust may also affect the
amount of material, although data are insufficient
to prove this contention.
Acetone Wash and Chloroform-Ether Extract Residues
The residues from the acetone wash and from the
chloroform-ether extracts averaged 29.7 percent of
the material caught after the filter since the residue
from the impinger water wash averaged 70.3 percent.
FIELD ANALYSIS
[ | LABORATORY ANALYSIS
ACETONE
EXTRACT
WATER
WASH
METAL
ANALYSIS
Fig. 5 Analysis of Particulate Catch after Filter
Table 11
Emission Spectrographic Analysis
of Impinger-Water Residue for Metals
Element
Barium
Manganese
Magnesium
Molybdenum
Lead
Chromium
Nickel
Iron
Aluminum
Calcium
Quantity
(ppm by weight)
Sample Sample
No. 1 No. 2
<0.5 <0.5
<0.5
-------
Impinger Water Residues
In an effort to identify residue from the impinger
water, two samples from Study G were analyzed
spectrographically. The results of this analysis
(Table 11) indicate that approximately 0.05 percent
of the impinger water residue was metal.
In addition, all eight impinger residue samples
from Study F were combined into one sample for
wet-chemical analysis for inorganics and instru-
mental analysis for organics, and 15 impinger
residue samples from Study G were combined and
analyzed in a similar manner. Approximately 28 and
43 percent, respectively, of these residues were
acetone soluble (Table 12). Sulfates were present in
approxiamtely 32 and 20 percent, respectively. The
acetone extract of both samples showed carbonyl
and aromatic bands in the infrared (presumably de-
rived from polynuclear compounds). No hydroxyl or
aliphatic bands were noted.
These analyses of the material caught after the
filter indicate that perhaps some of it should be re-
ported as particulates and some should not. The
organics and metals would probably condense in the
atmosphere to form particulates. The chlorides,
sulfates, and phosphates may be formed by gases
reacting with cations to form particulates while in
close contact in the impinger water. If so, they
probably would not react if emitted to the atmosphere
and would not fall within the category of particulates.
Further work is needed on identifying composition of
impinger water residues and their origin since this
work was primarily screening.
INCINERATOR EFFICIENCY
The efficiencies of the incinerators studied were
measured by calculating the reduction in weight,
Table 12
Analyses of Impinger-Water Residue
Analysis
Incinerator F
Incinerator G
Acetone extract
Chloride
Sulfate
Phosphate
Hardness
Iron
pH of water solution
28.3%
1.0%
31.8%
0.2%
25.47°
s Iron g
2.8
42.9%
0.3%
20. 1%
0.2%
4.5%
percent
3.0
volume, volatiles, and the amount of available heat
released (Table 13). The weight reduction is cal-
culated from the dry weights of solid waste, residue,
and fly ash. The volatile reduction is calculated
from the volatile content of these materials, and
the heat released is based upon their heat content.
The volume reduction was calculated from the wet
densities and weights of solid waste and residue.
Although the amount of solids in the wastewater
should be included in efficiency calculations, the
quantity of wastewater was not measured and cannot
be included. Estimates indicate this effect is small.
For all practical purposes, no real distinction
can be made between any of the incinerators studied
when efficiencies are based on volatile or volume
reduction or heat released. It should be pointed out,
however, that the incinerators studied were selected
because they were noted for achieving "good burnout"
Because the degree of weight reduction is inversely
proportional to the amount of noncombustibles in the
waste, it is not a good indicator of incinerator ef-
ficiencies. Better indicators are the volatile and
volume reduction and the amount of available heat
released.
Economics
Annual Costs
The actual annual costs for the municipal-sized
incinerators (A, B, D, E, F, and G) varied from
$171,838 to $675,864 (Table 14) and correspond to
unit costs from $4.02 to $6.69 per ton of waste
processed. Incinerator C was a pilot plant, and
meaningful cost data were not available.
Table 13
Incinerator Efficiency
Weight Volatile Heat Volume
Incinerator Reduction Reduction Released Reduction
A
B
C
D*
E
F
G
61
68
62
-
63
72
53
98
99
99
-
98
97
99
98
99
99
-
97
96
99
(*)
(*)
(*)
-
95
97
94
* Measurements not made.
52
-------
en
CO
Table 14
Annual Cost Data
Incinerator A
Item
Operating costs:
Direct labor
Utilities
Parts and supplies
Vehicle operations
External repairs
Disposal charges
Overhead
Total operating cost
Operating cost/ ton
FinancingBs ownership costs:
Plant depreciation
Vehicle depreciation
Interest
Total financing and
ownership cost
Financing and
ownership cost/ ton
Total cost
Total cost/ ton
Normal
Actual
$75,184
17,352
12,509
1,739
7,346
700
11,326
126,156
2.95
23,581
6,042
16,059
45,682
1.07
171,838
4.02
Capacity
Adjusted
$73,703
17,352
12,509
1,739
7,346
700
11,326
124,675
2.92
21,651
6,042
32,477
60,170
1.41
184,845
4.33
Design
Projected
$112,776
35,135
24,608
3,421
14,451
1,377
11,326
202,094
2.41
23,581
6,042
16,059
45,682
0.54
247,776
2.95
Capacity
Adjusted
$110,555
34,135
24,608
3,421
14,451
1,377
11,326
199,873
2.38
21,651
6,042
32,477
60,170
0.72
260,043
3.10
Normal
Actual
$197,500
20,000
32,950
7,200
6,250
2,000
52,800
318,700
4.90
80,149
9,675
64,558
154,382
2.38
472,082
7.28
Incinerator B
Capacity
Adjusted
$185,730
20,000
32,950
7,200
6,250
2,000
52,800
306,930
4.72
84,842
9,675
127,262
221,779
3.41
528,709
8.13
Design
Projected
$197,500
25,850
42,580
9,300
8,080
2,580
52,800
338,690
4.03
80,149
9,675
64,558
154,382
1.84
492,072
5.87
Capacity
Adjusted
$185,730
25,850
42,580
9,300
8,080
2,580
52,800
326,920
3.89
84,842
9,675
127,262
221,779
2.64
548,699
6.53
Normal
Actual
$193,138
18,000
0
7,670
22,339
32,232
32,959
306,338
2.35
200,000
0
70,448
270,448
2.07
576,786
4.42
Incinerator D
Capacity
Adjusted
$186,301
18,000
0
7,670
22,339
32,232
32,959
299,501
2.29
142,572
0
213,858
356,430
2.73
655,931
5.02
Design
Projected
$193,138
19,301
0
8,225
23,954
34,562
32,959
312,139
2.23
200,000
0
70,448
270,448
1.93
582,587
4.16
Capacity
Adjusted
$186,301
19,301
0
8,225
23,954
34,562
32,959
305,302
2.18
142,572
0
213,858
356,430
2.55
661,732
4.73
-------
Table 14(Contld)
cn
Incinerator E
Item
Operating costs:
Direct labor
Utilities
Parts and supplies
Vehicle operations
External repairs
Disposal charges
Overhead
Total operating cost
Operating cost/ ton
Financing& ownership costs:
Plant depreciation
Vehicle depreciation
Interest
Total financing and
ownership cost
Financing and
ownership cost/ ton
Total cost
Total cost/ton
Normal Capacity
Actual
$202,407
65,260
57,332
4,188
1,999
0
123,577
454,763
4.50
110,726
3,516
106,859
221,101
2.19
675,864
6.69
Adjusted
$205,139
65,260
57,332
4,188
1,999
0
123,577
457,495
4.53
168,574
3,516
252,860
424,950
4.20
882,445
8.73
Design Capacity
Projected
$202,407
90,418
79,433
5,802
2,770
0
123,577
504,407
3.60
110,726
3,516
106,859
221,101
1.58
725,508
5.18
Adjusted
$205,139
90,418
79,433
5,802
2,770
0
123,577
507,139
3.62
168,574
3,516
252,860
424,950
3.04
932,089
6.66
Incinerator F
Normal Capacity
Actual
$165,684
67,632
51,540
9,600
12,758
10,364
84,674
402,252
2.49
80,000
0
75,840
155,840
0.97
558,092
3.46
Adjusted
$181,391
67,632
51,540
9,600
12,758
10,364
84,674
417,959
2.59
121,795
0
182,693
304,488
1.89
722,447
4.48
Design Capacity
Projected
$165,684
70,500
53,725
10,007
13,299
10,803
84,674
408,692
2.43
80,000
0
75,840
155,840
0.93
564,532
3.36
Adjusted
$181,391
70,500
53,725
10,007
13,299
10,803
84,674
424,399
2.53
121,795
0
182,693
304,488
1.81
728,887
4.34
Incinerator G
Normal Capacity
Actual
$150,949
31,952
2,700
13,968
808
27,720
21,331
259,428
5.49
101,234
0
81,494
182,728
3.87
442,156
9.36
Adjusted
$145,434
31,952
2,700
13,968
808
27,720
21,331
243,913
5.17
111,722
0
167,583
279,305
5.91
523,218
11.08
Design Capacity
Projected
$160,949
75,777
6,403
33,127
1,916
65,741
21,331
365,244
3.26
101,234
0
81,494
182,728
1.63
547,972
4.89
Adjusted
$145,434
75,777
6,403
33,127
1,916
65,741
21,331
349,729
3.12
111,722
0
167,583
279,305
2.50
629,034
5.62
-------
The adjusted projected annual cost at design
capacity was also determined (Table 14). All in-
cinerators were operated below design capacity on
an annual basis because of insufficient waste or
equipment downtime; this was not true, however,
during the study periods. The projected costs were
determined by prorating costs that depend on the
quantity of material processed (actual vs. design).
The costs that vary with the amount of material pro-
cessed are utilities, parts and supplies, vehicle
operations, external repair charges, and residue
disposal charges. With one exception (Incinerator A),
labor costs did not increase significantly with the
amount of waste processed because all facilities
studied were staffed for operation at full capacity.
Incinerator A was operating on a two-shift basis, and
projection to design capacity required the addition
of another shift. To determine the annual design
capacity, the daily design capacity was multiplied
by 280 operating days. To illustrate this projection,
Incinerator A, with a design capacity of 84,000 tons/
year (300 tons/day x 280 days), actually processed
42,700 tons of waste. The projected utility costs for
processing 84,000 tons was $34,135, an increase
from the actual cost, $17,352.
The projected annual cost data were also adjusted
to a common reference point so that the data from the
various incinerators could be compared (Table 14).
The primary items requiring adjustment are labor
costs, plant depreciation, and interest. To adjust
labor cost to reflect similar wage rates, the actual
cost was multiplied by $3.00 and divided by the
average hourly labor cost for the facility (which for
Incinerator A was $3.06). Thus, the adjusted labor
TOTAL ANNUAL COST
cost for Incinerator A was $73,703, down from the
actual cost of $75,184. To adjust the plant
depreciation and interest charges, it was assumed
that plant life is 25 years, simple interest charges
are 6 percent, and construction started 2 years before
the facility began operating. Capital costs were
adjusted to the year 1967 with the use of a con-
struction cost index. This construction cost index
was developed from three sources [8-10], Unpublish-
ed data developed by the American Society of Civil
Engineers and The American Society of Mechanical
Engineers show that the capital costs for construct-
ing incinerators are divided between building and
equipment in a 60:40 ratio [8]. As a result, 60 per-
cent of a building cost index [9] and 40 percent of
an equipment cost index [10] were used to develop
the facility cost index:
Year
Index
INCINERATOR
Fig. 6 Total Annual Costs of Incinerators
1967 1.0000
1966 1.0526
1965 1.1036
1964 . . / 1.1476
1963 1.1881
1962 1.2326
1961 1.2687
To adjust interest charges, the adjusted capital
costs were multiplied by the 6 percent interest
charged. For Incinerator A, the adjusted interest
charges were $32,477, up from the actual $16,059.
To calculate the adjusted plant depreciation, the
adjusted capital costs were divided by the assumed
25-year plant life.
Comparison of adjusted annual costs for a per ton
of solid waste processed shows that financing and
ownership costs (Fig. 6) are a significant portion of
the total costs.
Comparison of actual costs with projected costs
shows the effect of operating the incinerator at less
than design capacity (Fig. 7). Operating an inciner-
ator at less than design capacity, as shown by the
data for Incinerator G, can be quite expensive.
(Note that the data for Incinerator G were for the
first year of operation and that the facility presently
operates near design capacity.)
When a new incinerator is designed, facilities for
handling future quantities of waste should be care-
fully considered. If the size of the plant is too large,
it is implied that the cost of "idle" equipment may
be excessive. These data tend to reinforce the con-
cept of building a facility to dispose of the current
amount of solid waste with provisions for adding
55
-------
11.00
10.00
9.03
1 '-•»
- 600
i
K
§ 5.00
300
ACTUAL COST PER
TON (ADJUSTED)
PROJECT ED COST
PER TON (ADJUSTED)
D E
INCINERATOR
Fig. 9 Percentage Distribution of Operating Costs by
Cost Center
INCINERATOR
Fig. 7 Projected Costs at Design Capacity and Actual
Costs of Incinerators
[ | UTI
REPAIRS AND
MAINTENANCE
S 4.00
8 3.00
1.00
_ 100'.
f
100%
100°;
100'.
A B D E F
INCINERATOR
Fig. 8 Operating-Cost Breakdown by Expenditure Type
56
-------
additional combustion units as required. This is too
simple a picture, however; increasing construction
and interest costs may override this concept.
Capital Costs
Capital investment in the incinerators studied
varied from $1,800 to $8,400 per ton of design
capacity (Table 15). Because Incinerator A did not
To identify the capital costs further, investments
in buildings, equipment, and miscellaneous items
were analyzed (Table 16). (Note that the incinerators
analyzed were very different in construction and
design.)
Table 16
Breakdown of Capital Investment
have scales, residue quench tanks, a crane (charging
was with a front-end loader), or a storage pit, the
capital requirements were obviously less.
Plant Adjusted Cost Percent of Total
Incinerator A:
Buildings $191,979 35.5
Table 15
Analysis of Capital Investment
Actual Adjusted Adjusted
Incinerator Cost Cost Cost/Ton
A $471,659 $541,276 $1804
B 1,848,240 2,121,040 7070
D 3,000,000 3,564,300 7129
E 3,321,779 4,214,341 8429
F 2,400,000 3,044,880 5075
G 2,530,855 2,793,052 6983
70
60
i
5
uj
a 50
o:
s.
r—
8 40
O
CK
LU
Q_
° 30
O
h-
o
z 20
LU
U
Q.
10
Q
69°,
7°
I
%
%
%
*/
^
^
^
)
"i
i
1
i
%
%
X
1
^
1
P
15'. K:
I
%
59%
slllllllllllllllllH
3, u
«|{«P
^
^
x!
^
^
!
1
i
\
16%
S !H =
::: w=
*°W^
. . ^A —
A B D
Equipment 333,977 61.7
Miscellaneous 15,320 2.8
Total 541,276 100.0
Incinerator B:
Buildings 1,428,119 67.3
Equipment 530,593 25.0
Miscellaneous 162,328 7.7
Total 2,121,040 100.0
Incinerator E:
Buildings 1,312,506 31.2
Equipment 2,711,198 64.3
Miscellaneous 190,637 4.5
44'.
^ 27
% 11
$ |l
\ il
rfc I1
JIlB
E
Total 4,214,341 100.0
W LABOR
59',
52%
y>
r/^
^
"I
^
24',
14'.!=
°'' XA==
p. n
$'• '° Mp
V
^
^
^
•4,
i
I
i
E£Xvl UTILITIES
••B VEHICLE
^•B OPERATION
KM2 REPAIRS
^ __] OVERHEAD
17% I6"a
1
I'll
F G
INCINERATOR
Fig. 10 Receiving Cost Center: Percentage Distribution
of Operating Costs by Expenditure Type
57
-------
01
CO
Table 17
Repairs and Maintenance Cost Data
Item
Expenditure type:
Labor
Parts
External charges
Overhead
Total
Cost center:
Receiving and handling
Volume reduction
Effluent handling & treatment
Total
Incinerator A
Actual
$10,442
12,509
7,346
1,574
31,871
$6,824
21,641
3,406
31,871
Adjusted
$10,237
12,509
7,346
1,574
31,666
$6,780
21,502
3,384
31,666
Incinerator B Incinerator D
Actual
$29,625
32,951
6,250
7,919
76,745
$9,112
56,825
10,808
76,745
Adjusted Actual
Expenditures
$27,861 $53,590
32,951 0
6,250 22,339
7,919 9,145
74,981 85,074
Allocation
$8,903 $13,766
55,518 60,109
10,560 11,199
74,981 85,074
Adjusted
$51,695
0
22,339
9,145
83,179
$13,460
58,770
10,949
83,179
Incinerator E
Actual
$61,335
57,332
1,999
37,447
158,113
$39,345
85,597
33,171
158,113
Adjusted
$62,164
57,332
1,999
37,447
158,942
$39,552
86,045
33,345
158,942
Incinerator F
Actual
$31,679
51,540
12,758
16,189
112,166
$17,960
77,804
16,402
112,166
Adjusted
$34,685
51,540
12,758
16,189
115,172
$18,442
79,888
16,842
115,172
Incinerator G
Actual
$44,003
2,700
808
6,799
54,310
$18,642
17,834
17,834
54,310
Adjusted
$39,762
2,700
808
6,799
54,069
$17,187
16,441
16,441
50,069
-------
Table 18
Operating Cost Breakdown by Cost Centers
01
Cost Center
• —
Receiving and handling:
Direct labor
Utilities
Vehicle operating expense
Repairs and maintenance
Overhead
Total
Volume reduction:
Direct labor
Utilities
Repairs and maintenance
Overhead
Total
Effluent handling and treatment:
Direct labor
Utilities
Vehicle operating expense
Disposal charges
Repairs and maintenance
Overhead
Total
Total
_
Incinerator A
Actual
$25,062
0
1,564
6,824
3,775
37,225
35,504
8,597
21,641
5,348
71,090
4,176
8,755
175
700
3,406
629
17,841
126,156
Adjusted
$24,568
0
1,564
6,824
3,775
36,731
34,805
8,597
21,641
5,348
70,391
4,094
8,755
175
700
3,406
629
17,759
124,881
.
Incinerator B
Actual
$79,000
3,020
0
9,112
21,119
112,251
59,250
7,480
56,826
15,839
139,395
29,625
9,500
7,200
2,000
10,809
7,920
67,054
318,700
Adjusted
$74,290
3,020
0
9,112
21,119
107,541
55,720
7,480
56,826
15,839
135,865
27,860
9,500
7,200
2,000
10,809
7,920
65,289
308,695
.
Incinerator D
Actual
$51,942
12,600
0
13,766
8,864
87,172
48,451
2,700
60,108
8,268
119,527
39,156
2,700
7,670
32,232
11,199
6,682
99,639
306,338
Adjusted
$50,103
12,600
0
13,766
8,864
85,333
46,736
2,700
60,108
8,268
117,812
37,770
2,700
7,670
32,232
11,199
6,682
98,253
30r,398
Incinerator E
Actual
$67,470
6,964
0
39,345
41,192
154,971
30,667
7,724
85,597
18,725
142,713
42,935
50,572
4,188
0
33,171
26,213
157,079
454,763
^ _
Adjusted
$68,381
6,964
0
39,345
41,192
155,882
31,081
7,724
85,597
18,725
143,127
43,515
50,572
4,188
0
33,171
26,213
157,659
456,668
..
Incinerator F
Actual
$59,294
12,715
0
17,960
30,302
120,271
34,226
8,251
77,804
17,492
137,773
40,485
46,666
9,600
10,364
16,402
20,691
144,208
402,252
Adjusted
$64,915
12,715
0
17,960
30,302
125,892
37,471
8,251
77,804
17,492
141,018
44,323
46,666
9,600
10,364
16,402
20,691
148,046
414,956
Incinerator G
Actual
$73,360
18,720
0
18,642
9,081
119,803
14,260
6,193
17,834
1,819
40,106
29,325
77,039
13,968
27,720
17,834
3,632
99,519
259,428
— • i—
Adjusted
$66,288
18,720
0
18,642
9,081
112,731
12,885
6,193
17,834
1,819
38,731
26,498
7,039
13,968
27,720
17,834
3,632
96,691
248,153
-------
Operating Costs
The operating costs were analyzed to determine
the relationship between labor, utility, and repair
and maintenance costs. In all cases, labor costs
were highest and utility costs, lowest (Fig. 8). A
breakdown of the repair and maintenance costs and
allocation to cost centers was made (Table 17).
Analysis of operating costs by cost centers
shows no real trend between the three cost centers
(Table 18, Fig. 9). Analysis of the operating cost
for the receiving cost center shows, however, that
10 -
LABOR
UTILITIES
REPAIR
OVERHEAD
D E
INCINERATOR
Fig. 11 Volume-Reduction Cost Center: Percentage Dis-
tribution of Operating Costs by Expenditure Type
fi 20
to
LABOR miiUJ CHARGES
UTILITIES [fflfflVjl REPAIR
olSSSoN EZI OTERH"°
32°,
D E
INCINERATOR
Fig. 12 Effluent-Handling Cost Center: Percentage Dis-
tribution of Operating Costs by Expenditure Type
60
-------
labor costs average 58 percent and far exceeded all
other costs (Fig. 10). This would tend to indicate
that costs in this center might be reduced by auto-
mating the operations. Analysis of operating costs
for the volume-reduction cost center shows that
labor and repair costs are the major expenditures
and average 35 and 47 percent, respectively (Fig. 11).
Analysis of operating costs for the effluent handling
cost center shows no definite trend between the
various items (Fig. 12).
CONCLUSIONS
For disposal of solid waste, these incinerators
functioned well; reduction of volume and volatiles
and the amount of heat released were greater than
94 percent in all cases and in some cases approach-
ed 99 percent.
The proper treatment and disposal of incinerator
effluents has generally been neglected at these
facilities. Process waters were contaminated, and,
although several plants have primary treatment
facilities, further treatment is required before dis-
charge to a watercourse. Particulate emissions were
in excess of all but the most lenient air-pollution-
emission standards. The quality of the effluents
could be improved, however, by increasing invest-
ment in pollution-control equipment.
Labor costs were the major portion of operating
costs at every facility. Capital costs varied widely
at these facilities without affecting the quality of
the effluents.
ACKNOWLEDGMENTS
The excellent assistance and cooperation extend-
ed by the staffs of the seven incinerators, including
administrative personnel, contributed to the success-
ful completion of these studies. The analytical sup-
port, laboratory assistance, and facilities provided
by county and State health departments, sanitation
authorities, and universities are greatly appreciated.
The credit for the success of these studies
belongs to the study team members. Among others,
the authors would like to acknowledge the efforts of
J. Giar, A. O'Connor, I. Cohen, J. Hahn, T. Hegdahl,
R. Perkins, and J. Bridges, all of the Bureau of
Solid Waste Management.
REFERENCES
[l] D. E. Carruth and A. J. Klee, "Analysis of Solid
Waste Composition; Statistical Technique to Determine
Sample Size," U.S. Department of Health, Education, and
Welfare, Cincinnati, Ohio, 1969.
[2] "Standard Methods for the Examination of Water
and Wastewater; Including Bottom Sediments and Sludges,"
American Public Health Association, American Water
Works Association, and Water Pollution Control Federation,
American Public Health Association, Inc., New York, N.Y.,
12th ed., 1965.
[3] "Specifications for Incinerator Testing at Federal
Facilities," National Center for Air Pollution Control,
U.S. Department of Health, Education, and Welfare,
Durham, N. C., October 1967.
[4] E. R. Zausner, "An Accounting System for In-
cinerator Operations," U.S. Department of Health, Educa-
tion, and Welfare, Cincinnati, Ohio, 1969.
[s] E. Zausner and R. L. Helms, "Computerized
Economic Analysis for Incineration," U.S. Department of
Health, Education, and Welfare, Cincinnati, Ohio,
(In press).
[6] T. L. Stumph and R. L. Duprey, "Trends in Air
Pollution Control Regulations," paper presented at 62nd
Annual Meeting, Air Pollution Control Association, New
York, June 22-26, 1969.
[7] "Air Pollution Control Standards for Particulate
Emissions," National Air Pollution Control Administration,
Training Lecture Outline for Elements of Air Quality
Management Course; U.S. Department of Health, Education,
and Welfare, 1966.
[s] Unpublished data for the years 1940 to 1956,
Solid Waste Engineering Section, Committee on Sanitary
Engineering Research, ASCE; unpublished data for the
years 1953 to 1968, Task Group of design Subcommittee,
ASME.
[9] "Indexes for Updating the Costs of General or
Special Buildings," Engineering News Record, vol. 180,
no. 12, March 21, 1968, pp. 84-85.
[lO] "General Purpose Machinery and Equipment
(Code 11-4) Wholesale Price Index," U.S. Department of
Labor, Bureau of Labor Statistics, Washington, D. C.,
March 1966.
61
-------
APPENDIX: PHYSICAL DESCRIPTIONS OF
INCINERATORS STUDIED
Incinerator A
Year Built - 1966.
Design Capacity (tons/24 h) - 300.
Solid-Waste Storage and Charging System — Dumped
on enclosed tipping floor and transported to
charging hoppers by a front-end loader; con-
tinual feed from hoppers by conveyors.
Furnace Type and Components — Two refractory-
lined, multiple-chambered furnaces with in-
clined, modified reciprocating grate sections
followed by stationary grate sections.
Air-Draft System - An 11,000-ft 3/min forced-draft
underfire-air fan and a 57,000-ft3/min induced-
draft fan per furnace; no overfire air.
Residue-Handling System - Common chain flight
conveyor for both furnaces; partial spray
quenching.
Air-Pollution-Control System —Wet scrubber:
impingement on 42 12-in. diameter wetted
columns.
Effluent-Water Systems -Residue-quenching water
flows to complete retention lagoons. Fly-ash
scrubbing water flows to settling basins and
then to complete retention lagoons.
Date Studied- April 1968.
Local ion -Western United States.
Incinerator B
Year Built-1966.
Design Capacity (tons/24 h) - 300.
Solid-Waste Storage and Charging System-Enclosed
tipping floor; 3,000-yd3 storage pit; one bridge
crane with grapple bucket; two charging hoppers.
Furnace Type and Components — Two refractory-
lined, multiple-chambered furnaces with three
sections of inclined rocking grates.
Air-Dra/rSysfem-Two 19,000-ft3/min forced-draft
fans for each furnace and one 200-ft-tall stack
for natural draft.
Residue-Handling System — Quench tank with chain
flight conveyor; duplicate system available.
Air-Pollution-Control System —Viet scrubber: flooded
baffle walls.
Effluent-Water Systems — Fly-ash scrubbing water-
receives pH adjustment, detention in settling
basin, and is discharged weekly to sewerage
system. Residue-quench water is detained in
settling basin and discharged weekly to
sewerage system.
Date Studied-May 1968.
Location — Eastern United States.
Incinerator C
Year Built-1967.
Design Capacity (tons/24 h)-5 to 6 (1000 Ib/h for
10 to 12 h).
Solid-Waste Storage and Charging System —Pilot
plant; no permanent storage; charging by screw
conveyor from hopper.
Furnace Type and Components —Conical burner;
double metal walls; fixed grates.
62
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Air-Draft System -An I,800-ft3/min forced draft
underfire-air fan and 3600- (water scrubber) or
5000-ft3/min (electrostatic precipitator)
induced-draft fan.
Residue-Handling System — Manual cleanout after
cooling period.
Air-Pollution-Control Systems - Water scrubber:
centrifugal type; afterburner and water scrubber;
electrostatic precipitator.
Effluent Water Systems — Fly-ash scrubbing water
flows to settling basin and final discharge to
open watercourse.
Date Studied-July 1968.
Location— Southern United States.
Air-Draft System-A. 25,000-ft3/rnin forced-draft,
underfire-air fan per furnace and one 200-ft-tall
stack for natural draft.
Residue-Handling System - Residue-quench tank
with chain flight conveyor; duplicate system
available.
Air-Pollution-Control System-Viet scrubber: water
sprays and a baffle wall.
Effluent-Water Systems - Fly-ash scrubbing water
is also used for residue quenching; it then
flows through a grit chamber before discharge
to open watercourse.
Date Studied- December 1968.
Location — Southern United States.
Incinerator D
Year Built-1965.
Design Capacity (tons/24 /ij-500.
Solid-Waste Storage and Charging System—Open
tipping floor; two storage pits; two bridge
cranes; two charging hoppers.
Furnace Type and Components — Two refractory-
lined, multiple-chambered furnaces with two
. sections of traveling grates (one inclined and
one horizontal).
Air-Draft System —Forced-draft fan and natural draft
from 200-ft-tall stack for each furnace.
Residue-Handling System — Quench tank with chain
flight conveyor; duplicate system available.
Air-Pollution-Control System-Wet scrubber: flooded
baffle walls.
Effluent-Water Systems — All process water flows
through a settling basin and then to sewerage
system.
Date Studied-October 1968.
Location — Midwestern United States.
Comments — One of two furnaces was out of operation
during the week of the study; in an effort to
process as much waste as possible, the other
furnace was overloaded.
Incinerator E
Year Built-1963.
Design Capacity (tons/24 Aj-500.
Solid-Waste Storage and Charging System-Open
tipping floor; 5150-yd3 storage pit; two bridge
cranes; two charging hoppers.
Furnace Type and Components — Two furnaces with
three reciprocating grate-sections followed by
a rotary kiln.
Incinerator F
Fear Built -1963.
Design Capacity (tons/24 h) - 600.
Solid-Waste Storage and Charging System —Open
tipping floor; 2430-yd3 storage pit; two bridge
cranes; two charging hoppers.
Furnace Type and Components—Two furnaces with
three reciprocating grate sections followed by
a rotary-kiln section.
Air-Draft System-A 25,000-ft3/min forced-draft,
underfire-air fan per furnace and one 200-ft-tall
stack for natural draft.
Residue-Handling System — Residue-quench tank
with chain flight conveyor; duplicate system
available.
Air Pollution Control System — Wet scrubber: water
sprays and a baffle wall.
Effluent Water Systems — Fly-ash scrubbing water is
also used for residue quenching: it then flows
through a lagoon before discharge to open
watercourse.
Date Studied- December 1968.
Location — Southern United States.
Comments — One of the two furnaces was out of
operation during the study.
Incinerator G
Fear Built -1967.
Design Capacity (tons/24 h) - 400.
Solid-Waste Storage and Charging System-Open
tipping floor; 1750-yd3 storage pit; one bridge
crane; two charging hoppers.
Furnace Type and Components-Two furnaces with
four sections of inclined reciprocating grates.
63
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Air-Draft System-A. 20,000-ft3 min forced-draft Air-Pollution-Control System -Multitube dry cyclones
underfire air, 24,000-ft3 min forced-draft over- following a wet-baffle wall.
fire air, and 120,000-ft3 min induced-draft fan Effluent-Water Systems - All process waters enter
per furnace. residue-quench tank and then go to a lagoon
Residue-Handling System — Residue quench tank with discharge to a canal.
with chain flight conveyor; duplicate system Date Studied— February 1969.
available. Location - Southern United States.
64
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An Evaluation of Seven Incinerators
W.C. ACHIIMGER and I.E. DANIELS
DISCUSSION by David L. Brenchley, Purdue Univer-
sity, Lafayette, Ind.
The authors and their colleagues are to be compli-
mented on their efforts on this rather ambitious pro-
ject. As indicated by the authors, there is a great
need for such operational and cost information.
In conducting their evaluation the authors found
and reported their frustrations concerning the need for
standardized methods for incinerator testing and
evaluation. Unfortunately this project became en-
tangled with the problems of sampling, analysis, and
testing methodology. Since standard methods do not
exist at this time, I feel the authors should have been
more detailed in describing the procedures used.
One of the objectives of this study was to evalu-
ate the potential impact of the incinerator operation
on the environment. This has not been adequately
achieved! Some process water quality tests are
reported in Table 8 but there is no information on
quantities of water used. With respect to air pollu-
tion, only measurements for particulate matter, car-
bon monoxide, carbon dioxide and oxygen were re-
ported. Obviously, more measurements should have
been taken to properly evaluate the air pollution
potential.
The use of the "cost center" approach is most
enlightening, as indicated in Tables 14, 17, and 18.
However, it should be noted that none of the munici-
pal incinerators tested met the particulate emission
standards established by regulative organizations
such as Los Angeles and the state of New Jersey.
It would be most interesting to know what the total
cost per ton would be if these installations were re-
quired to meet these air pollution control regulations.
Finally, I wish to emphasize that the cost infor-
mation presented should not be used as the basis for
selecting a particular incinerator design. The varia-
tion of waste composition, differing operational
characteristics, and the test methodology itself
strongly influence the results.
DISCUSSION by P. B. Hall, Director of Public Works,
City of Alexandria, Ya.
The subject paper "An Evaluation of Seven In-
cinerators" presents data relating to design, opera-
tion and costs which should be carefully considered
in future incinerator design. It is impossible, in the
time allotted, to fully discuss the paper; too many
important factors are contained in it.
I would like to confine my remarks to two particu-
lar sections of the paper; the section on Stack Efflu-
ents and the section on Costs.
Referring to the Stack Effluent tests, I am not
satisfied that the present techniques for sampling
will give accurate or even meaningful results. While
I do not quarrel with the conclusion that more sophis-
ticated methods of pollution control must be eventual-
ly instituted, I feel that the data presented in the
paper give an unfair picture of the actual operating
results. Until a system of collecting flue gases on a
constantly monitored basis is evolved, intermittent
stack tests cannot be relied upon. The constantly
varying nature of the fuel, climatic conditions occurr-
ing during the test and variations in operating proce-
dures to properly burn a non-homogeneous fuel make
such intermittent tests indicative only of a particular
condition under particular circumstances. The need
for a permanently installed fly ash monitoring system
must receive priority consideration.
It should also be pointed out that, unless we can
get the results of the stack effluent tests as soon as
possible after they are made, it is very difficult to
correlate them with the operating conditions existing
at the time of the tests. Thus we are not able to
effectively make operating changes to correct un-
satisfactory effluent results. I see no realistic an-
swer at present until a constant monitoring system
can be put into daily use.
The cost data presented are interesting but not
necessarily conclusive unless all units studied are
reporting on the same basis. Budgetary format,
-------
handling of charges for major repairs (are these
spread out over the life of the repair or costed en-
tirely at the time of making the repair) and overhead
allocations may present a distorted picture. In this
connection, the current A.P.W.A. study on "Compara-
tive Public Works Statistics" may point the way
toward more meaningful data of this type.
As you have probably surmised, the incinerator
which is operated by my City was one of those tested.
I would like to express my appreciation to the offi-
cials and staff of the Bureau of Solid Waste Manage-
ment for their efforts to give us a picture of what
actually goes on in the incineration process; their
cooperation has been excellent, even though, as I
remarked, I have doubts as to some of their final
results.
DISCUSSION by Fred R. Rehm, Milwaukee County
Department of Air Pollution Control, Milwaukee, Wise.
Mr. Achinger and Mr. Daniels (and their Associates)
are to be commended for this fine paper and for the
depth of the studies reported about the seven inciner-
ators evaluated.
One thing that bothered me somewhat in studying
the paper was the inclusion of the Pilot Plant test
data on the Conical Burner (Tepee) in their tables
right alongside those results derived from the more
conventional high burning rate, high heat-release
rate, high temperature refractory-lined going munici-
pal incinerators. The Tepee burner, of course, is a
separate beast unto itself. Therefore, the compari-
sons made in the various tables in the report must be
viewed with considerable care lest erroneous and
questionable conclusions be drawn when comparing
this rather distinctive pilot plant system with the
more conventional municipal incinerator.
It was fine that this pilot plant work was done.
What I am saying is that perhaps the results might
have been better presented as a separate paper to
avoid the possible misinterpretations that can, and
probably will, be made.
For some time now, I have been calling attention
to the rather basic problems created by NAPCA's
position with regard to the definition of "Particulate
Matter", as opposed to that definition which has
been in effect for many years and has been widely
accepted by the incinerator industry, the air pollu-
tion control equipment manufacturers, many air pollu-
tion control people and virtually the vast majority of
all interested groups working in this field. As you
know, ASME and most of these other groups have
defined and measured particulate as a dry, filtera-
ble solid. NAPCA has expanded this definition to
include liquids at standard conditions. And, of
course, Mr. Achinger and Mr. Daniels clearly point
out some of the questions that have been raised as
to whether the NAPCA sampling test train really
measures and reports particulate matter consistent
with its own definition. This paper helps a great
deal to draw into sharper focus this problem created
by the NAPCA proposed definition and its sampling
train. In this regard, the paper is a most worthwhile
addition and contribution to the field since it is one
of the first official Federal government publications
which illustrates in depth the basic problem area that
has its origin in this rather unique approach and
interpretation.
The data, as Mr. Achinger pointed out, clearly
show that "particulate" emissions "exceed all but
the most lenient air pollution emission standards";
emission standards, which, incidentally, were esta-
blished based upon the current prevailing definition
of particulates, and which were not meant to consider
absorbable gases, condensible vapors and their re-
action products as particulate matter.
This statement on emissions has particular mean-
ing when viewed alongside another statement made
in the Conclusions section of the paper which reads,
"For disposal of solid waste, these incinerators func-
tion well; reduction of volume and volatiles and the
amount of heat released were greater than 94 percent
in all cases—and in some cases approached 99 per-
cent." In other words, for the job they were designed
to do—that is to consume wastes—these incinerator
plants operated well.
I believe in the field of incineration, more than in
any other field or application, we tend to discredit
the whole or total system because the air pollution
performance requirement has become "the tail that
wags the dog." Having some personal familiarity
with some of these plants, I know that they have been
a "Godsend" to their communities in meeting the
local solid waste disposal crises—and frankly, the
air pollution problems created by these plants are
rather trivial in comparison to the problem that
existed from the on-site open burning or disposal
of these same wastes by private citizens, or by ill-
equipped small, private disposal firms. So I think
we must not, in our haste and impatience to reach
the Utopian or ultimate solution to our air pollution
problems, lose sight of the fact that while room for
much improvement still remains, many of these in-
cinerator plants have performed, and continue to
perform, a very worthwhile and needed function in
their particular communities.
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Since there is this great question mark about the
"particulate" definition problem and what it really
is that the NAPCA sampling train measures and
reports as particulates, I would like to make the
suggestion to Mr. Achinger and Mr. Daniels that
they promptly publish or make available for review
and scrutinity by ASME and APCA (and other
interested and concerned groups), the full and com-
plete test data relating to the air pollution tests of
these plants.
In reading over that part of this paper in which I
am most interested — the air pollution performance —
I had a great number of questions which I felt would
have a significant bearing on the air pollution per-
formance of these plants that were not touched on in
the paper. This data probably exists in the volumi-
nous files of field data that were taken at these
plants and which, of course, the limitations of an
ASME paper do not readily permit reporting upon.
I feel that answers to the following questions would
be helpful to an in-depth evaluation of the air pol-
lution test data presented here:
Operating Conditions
1. What were the plant conditions of operation
when each emission test was run? By this I mean:
a) What was the charge rate (as best as could be
determined) to the furnace during the actual air pol-
lution test run sampling periods?
b) What was the range of furnace and combustion
chamber temperatures during the actual sampling
periods?
c) What was the physical or apparent condition of
the control systems during the period of tests? We
all know that maintenance of many such plants leaves
much to be desired. And since all of these plants
were two to six years old at the time of testing, this
could be a significant factor in the test results.
d) What was the draft loss across the collector
system during the tests? This might provide an in-
sight as to the effectiveness of the design and/or to
the state or condition of the collection system.
Testing
I have always found it difficult to describe a
plant's air pollution performance by a single
"average" number whether I was describing grain
loadings, mass emission rate, excess air levels,
volumetric flows, etc., as given in Table 9. I sug-
gest that it would have been most helpful had the
authors provided an insight as to the ranges of each
of these indicators or parameters measured at each
plant - in addition to citing an "average" figure as
in Table 9 of the report. And, of course, air pollution
performance test results are invariably judged by the
maximum emission rates rather than the average
emissions.
I would like, too, to see what emission results
were obtained with various rates of operation and
with the charging of different characteristic refuse.
Table 1 of the paper showed the rather wide range of
daily refuse composition at one plant. And, of
course, we know that moisture content will vary
widely from day to day with local rainfall amounts
and seasonally — such as during the grass-clipping,
watermelon or corn-on-the-cob seasons.
I feel, too, that it would be helpful to know the
number of emission test runs made at each plant,
the range of the test results and the charge rate
condition associated with the sampling period.
Since the NAPCA test procedure itself is under
attack in some quarters, it would appear to be help-
ful to publish in greatest possible detail the data
that may help to answer such questions as:
a) What were the sample volume rates and
sample volumes used in each test run?
b) Does it appear that reproducible test results
were being achieved for what appeared to be approxi-
mately the same set of operating conditions? In
Table 10, there seems to be a wide range between
the high and low fraction of "condensables and
absorbables" measured at the same plant — ranging
as much as 25 to 1 at one of the plants. Are
reasonably reproducible results attained using the
low volume NAPCA test procedures and sampling
train?
c) No mention is made in the report on the visual
appearance (Ringelmann-wise or opacity-wise) of
the stack plume. This, too, is a fair indicator of
particulate emissions and often is a key to improper
operation. This information would be helpful in
evaluating the findings.
d) What was the distribution of the catch fractions
amongst the five different component groups in the
sampling train?
While some of these comments and suggestions
may appear to be very critical, they are certainly not
offered in that vein. I believe this paper and this
study to be a most important one and that a com-
mendable job has been done. If anything, my specific
criticisms might be summarized by stating that you
have done such a good job that you have really pre-
sented "too much" information of interest to too
many people to put it all into a single paper. And
what I hope my comments are taken to convey is that
I, for one, would like to see an in-depth paper pre-
-------
sented showing the full and complete test findings at
each of these plants in which additional attention
could possibly be given to some of the questions that
I have raised.
I might add, too, and this is not meant as a per-
sonal criticism but as a suggestion, that hopefully
the Federal Government paper release and technical
paper communication policy will improve since I
note that some of this test work was conducted more
than two years ago and is only now being made
public.
DISCUSSION by Charles 0. Velzy, Charles R. Velzy
Associates, White Plains, N.Y.
This paper is perhaps one of the most important
contributions to the field to be presented at the
Conference, not, however, because it gives us,
finally, adequate tools with which to develop
economical designs with confidence. Rather, it
serves to point up the need to conduct further, even
more comprehensive, coordinated studies, after wide
agreement on sampling methodology and analysis
techniques, as soon as possible with the results
released on a timely basis so that incinerator designs
can be rapidly optimized.
There seems to be a discrepancy in the informa-
tion presented in Table 2 with respect to Plants B
and G. Even though the actual capacity and the
actual burning rate per unit area of grate are higher
than the design capacity and rates noted, the actual
rate of heat release per unit volume is lower than the
design rate of heat release. This does not seem to
follow although perhaps the authors have an explana-
tion.
In Table 7, Fly-Ash Analyses, at plants B, C-3,
and G, the ratio of Heat, Dry Basis to Volatiles,
Dry Basis ranges around one hundred to one while at
plant A this ratio is about thirteen to one. Do the
authors have an explanation for this difference?
Was the composition of the fly-ash at plant A sig-
nificantly different than that collected at the other
plants and, if so, what were these differences and
what was the cause?
I would like to emphasize the authors' comments
to the effect that, "further work is needed on identify-
ing composition of impinger water residues and their
origin". This becomes particularly important when
one considers that this material, which we are un-
certain about as to quantity, origin, or health hazard,
has been lumped in with dry particulates in many
jurisdictions for purposes of determining Code
compliance. This is one of the few areas that I
know of where Code compliance is subject to ap-
parent measurement differences of 300 to 500 percent.
It is interesting to note, in Table 13, that at the
three plants where measurements were made, volume
reduction ranged from 94 to 97 percent or close to
that claimed for "high temperature" incinerators
even when weight reduction only ranged from 53 to
72 percent. This, plus inspections of the residue
from newer, conservatively designed plants, indicates
that so-called "conventional" incinerators are capable
of burning refuse to a point where it can be processed
for beneficial ultimate disposal.
The results presented in this paper indicate that
this method of refuse disposal has potential. How-
ever, the results also indicate that before the full
potential can be realized, much further investigation
and testing effort must be done so as to develop
adequate parameters for design and operation.
DISCUSSION by W. M. Harrington, Jr., Whitman,
Requardt & Associates, Baltimore, Md.
This paper shows the need for a well designed
standard incinerator test procedure which can be
used to determine operating efficiency, offer an
evaluation of the basic design concepts used in a
plant, reward operating efficiency, and allow the
determination of the firm operating capacity that a
plant can be considered capable of providing. With
the present high cost for providing modern, efficient
incinerators, it becomes vitally important to develop
information which will allow the design engineer to
provide the greatest amount of firm capacity at the
minimum cost. The only way to develop this infor-
mation is by extensive testing of existing facilities.
The U.S. Public Health Service effort offers a sig-
nificant beginning in this direction.
I suggest that the next step for the Public
Health Service is the development of a standard test
program which can be incorporated in construction
specifications and which will require all new
facilities to be tested as part of the initial start-up
procedure in order that the design can be evaluated
and the plant operating capacity fixed. If the test
procedure were standardized, test ports and other
provisions could be incorporated in the initial con-
struction at little additional project costs and the
testing job would be made easier. Periodic retesting
should be performed throughout the life of the plant
to indicate plant maintenance and operating efficiency
and allow re-evaluation of plant firm capacity in
10
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order to help prevent the overload operation so
prevalent in this country today.
DISCUSSION by Walter R. Niessen, Arthur D. Little,
Inc., Cambridge, Mass.
The authors are to be congratulated for the
quality work reported in this paper and for the com-
prehensive yet succinct method of presentation of
the data and experimental techniques. It is clear that
only through such detailed reporting and analysis of
system behavior can the state of incinerator tech-
nology be advanced through improved understanding
of the processes extant in the incinerator. There
are, however, three points that I would like to make
regarding studies of the type reported in this paper.
There is no mention made in the paper of the great
difficulty in obtaining a representative gas sample.
The data of Woodruff et. al. [1] suggests great
variation in the flue gas composition and temperature
throughout the flue gas ducts. It would be expected,
therefore, that a meaningful estimate of particulate
and gaseous air pollutant emission rates should
involve a rather complex integration of gas property
values (velocity, composition, temperature, etc.)
across the ducts rather than a single probe sample or
an average of samples at a single location. While
such tests are no doubt costly and difficult to carry
out, it would seem that the sizable sampling and
analysis team assembled for the tests described in
the paper would provide an excellent opportunity for
carrying out such a comprehensive sampling program.
I would suggest that a number of tests be made
ahead of the air pollution control device such that
one can begin to build a stronger causal relation-
ship, based on data, to relate incinerator design
and operating characteristics with emission rates.
Such data would also be of use in evaluating the
performance of the scrubbers or other air pollution
control devices installed on the units reported upon
and units to be tested in the future.
The third area where I would suggest that con-
sideration be given concerns an expansion of the
data-gathering activity to provide a comprehensive
statement of the operating conditions for the in-
cinerator during the test runs. To a large extent, the
tests described in this paper support such a charac-
terization in that the composition of the refuse
residue and the flue gas parameters are measured
and reported. It would be of great value, however, to
have documented, in some detail, such operating
variables as the quantity of forced air, divided be-
tween undergrate and overgrate air. These air flows
should be defined through measurement. I recognize
that in many cases the duct work in incinerators does
not make such tests easy to perform, but none the
less, such data would contribute greatly to our under-
standing of the interrelationship between aspects of
equipment performance and the operating and design
features of the unit. Because of the large number of
manual adjustments possible in incinerators (grate
speed, damper settings, etc.), the design data on fans
and other equipment does not provide sufficient infor-
mation to assess the plant operating characteristics.
References
[l] "Combustion Profile of a Grate-Rotary Kiln
Incinerator", P. H. Woodruff and G. P. Larson, Proc. of
1968 Incinerator Conference, pp. 327—36, ASME, New
York, 1968.
AUTHORS' CLOSURE
We wish to thank Messrs. Brenchley, Hall, Harring-
ton, Niessen, Rehm, and Velzy for the time they took
from their busy schedules to review and evaluate our
paper. We believe constructive criticism will in-
crease the rate at which technology advances in the
incinerator field.
It was obvious to us after reading these discus-
sions that we did not fully convey the intent of our
evaluation program. In undertaking this program, our
objectives are to develop reliable sampling
methodology and to identify the present capabilities
of incineration in this country.
The development of sampling methodology is an
evolutionary process. Therefore, we are continually
working to overcome the deficiencies the discussants
pointed out and other deficiencies as well. More
detailed descriptions of the testing procedures used
in these studies will be found in a testing manual
presently being developed.
Several discussants wanted more information than
was presented. As in any paper, the amount of ma-
terial we could include was restricted. However,
upon written request, more detailed information will
be made available.
Professor Brenchley wanted to know what effect
more efficient pollution control equipment would
have on the cost of incineration. We did not evaluate
this effect since our objective is to identify the costs
as they are and not as they might be. Undoubtedly,
though, this equipment would increase the cost of
incineration. We agree with Professor Brenchley's
statement that cost data should not be used as the
11
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sole criterion for selecting an incinerator design.
Mr. Hall questioned the reliability of test data
generated by 1 week of testing. We recognize that
a 1-week test is less reliable than a long-term test,
but until reliable continuous monitoring equipment be-
comes available, short-term testing programs must be
used.
Mr. Hall also questioned the comparability of the
cost data between the incinerators studied. As
pointed out in the paper, we adjusted the cost data
during analysis for differences in labor costs,
interest rates, depreciation rates, time of construc-
tion, and actual versus design capacity. To try to
avoid error during the collection process, our
economists used the same personnel to examine the
available cost records and to interview the people
who keep the records. Major repair items having a
long life, such as replacement of the grate system,
were costed out over their life expectancy. The re-
pair and maintenance costs include the yearly cost of
major repairs and the routine day-to-day charges.
Thus, we believe the cost data are comparable be-
tween incinerators.
Mr. Rehm questioned the advisability of including
pilot plant (Plant C) data with that from the other
municipal installations. We believe the data are
useful but should be interpreted with the reservation
that this plant is not a typical full-scale conical
burner.
Mr. Rehm wanted to know the reason for the ex-
treme variation in the figures for particulate caught
after the filter ("condensible")i particularly in
relation to Plant B (Table 10). Upon reviewing the
raw data used to calculate these values, we dis-
covered an error. The low value should be 6.6
instead of 0.7; thus, the average for Plan B is 14.3
instead of 13.6. Evaluating the ratio of high to low,
as suggested by Mr. Rehm, yields an average value
for all our studies of 2.3, with a range of 1.1 (C-3)
to 4.7 (D). We believe such variation is reasonable
when comparing two 1-hour tests for particulate
emissions at municipal incinerators.
Mr. Rehm and also Mr. Velzy stressed the im-
portance of identifying the constituents of the
"condensible" portion of the particulates. Since,
on the average, this condensible material is not
greater than 30 percent (Table 10), the urgency of
identifying these constituents is not too great. In
the case of Plant C-3, however, these materials
amounted to 73 percent of the total particulate. Be-
cause Plant C-3 uses a "high efficiency" electro-
static precipitator to control particulate air pollution
and the other plants use lower efficiency collectors,
the obvious conclusion is that as the efficiency for
collecting "dry" particulate increases, the per-
centage of "condensible" particulate leaving the
collector increases. Since the trend in air pollution
control is toward high efficiency particulate collectors,
controlling these condensible materials becomes
critical. We, therefore, agree with Messrs. Rehm and
Velzy that these materials, which are a form or air
pollution, must be identified so they can be efficient-
ly controlled. We are so concerned over the implica-
tions of this problem that we conducted some screen-
ing tests, as reported in the paper, in an attempt to
identify these compounds even though our objectives
do not include research-oriented goals.
Mr. Velzy pointed out a possible discrepancy be-
tween the design and actual heat release rates (Table
2) for Plants B and G. A discrepancy does not exist.
Even though the charging rates in both studies were
in excess of the design rate, the low heat content
of the incoming waste (Table 4) did not provide
enough heat to achieve design heat conditions.
The heat content of the fly ash from Plant B
(Table 7) should be 180 Btu/lb instead of 1,290.
Thus, the ratio, pointed out by Mr. Velzy, for Plants
A and B is about 13:1 and for Plants C-3 and G,
about 100:1. The only difference we can see is the
fly ash was collected in a water scrubber in Plants
A and B and in dry collectors in Plants C-3 and G.
Mr. Velzy commented on the apparent high degree
of volume reduction (Table 13) achieved by the
plants studied. This high reduction is related direct-
ly to the techniques we use to determine sample den-
sity of the incoming solid waste. This density is
determined by filling a 20-gallon container with un-
compacted waste and obtaining the net weight of the
waste. This procedure yields lower densities
(Table 4) than normally reported in the literature and,
thus, results in the high volume reduction. In the
absence of any standardized test for the density of
solid waste, we believe that any identified test,
consistently employed, could be used for com-
parative purposes.
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