A REPORT ON THE DEKALB COUNTY
INCINERATOR STUDY
This report (SW-Slts) was written by
Leland E. Daniels
U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
Environmental Health Service
Bureau of Solid Waste Management
1970
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Single copies of this publication will be distributed as supplies
permit. Address requests to the Bureau of Solid Waste Management,
Office of Information, 5555 Ridge Avenue, Cincinnati, Ohio ^5213-
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FOREWORD
Incineration is an important method of solid waste processing in
the United States, and although over 300 incinerators are in operation,
little information on the performance of these units is available. It
is therefore not surprising that the effects of incineration on the
environment are little understood and frequently ignored.
An incinerator discharges effluents into the environment in three
states: solid, liquid, and gaseous. The sources of these effluents
are the processes of combustion, gas cleaning, and residue quenching.
Any determination of the pollution contribution to the environment by
incineration must be concerned with all these effluents.
The Bureau of Solid Waste Management, through the Division of
Technical Operations, has initiated a testing program to characterize
the performance of incinerators of different designs and configurations.
The primary objectives of this program are to produce basic information
that identifies the results of the incineration process and to develop
reliable sampling methodology.
During the studies it is considered necessary to make a complete
analysis of all features that affect the operation of the facility as
well as those that influence its potential for environmental pollution.
The operation of the facility is not altered in any way unless specific
i i i
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study objectives dictate a change. Therefore, no special effort is
made to operate the facility at its design capacity; rather, it is
tested at its "operating" capacity.
Reports from each study in this program will be prepared primarily
for use by the management of the facility, although they will be
available upon request to other interested technical personnel. Each
report will contain only the data obtained during one individual
study. Data comparisons with other studies will not be made in
individual study reports. Summaries and comparisons of the data from
all studies (including comparisons), will be reported annually. Persons
interested in receiving these annual reports should contact the Office of
Information, Bureau of Solid Waste Management, 5555 Ridge Avenue,
Cincinnati, Ohio 45213-
--RICHARD D. VAUGHAN, Director
Bureau of Solid Waste Management
i v
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CONTENTS
INTRODUCTION 1
REPORT SUMMARY 3
Solid Waste 3
Residue ^
Plant Efficiency ^
Process Waters ^
Burning Rate "
Particulate Emissions 6
Economic Analyses «
Bacteriological Analyses 7
FACILITY DESCRIPTION 9
Solid Waste Handling 9
Combustion Unit 12
Residue Disposal I**
Air Pollution Control 15
Instrumentation 15
Plant Operation During Study 16
SAMPLING AND TESTING PROCEDURES 17
Solid Waste 19
Residue 20
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Particulate Emissions 2]
Process Waters 22
Economics 23
Bacteriological Analyses . . 23
RESULTS . 27
Solid Waste 2?
Residue 29
Plant Efficiency 33
Process Waters 34
Instrument Readings 34
Burning Rate 37
Particulate Emissions 37
Economic Analyses 41
Bacteriological Analyses 44
DISCUSSION 49
REFERENCES 51
ACKNOWLEDGMENTS 53
APPENDICES 55
A Example Calculations for the Ash, Volatile, and
Heat Content of the Solid Waste 57
B Example Calculations for the Ash, Volatile, and
Heat Content of the Residue 61
C Plant Efficiency Calculations 65
D Example Calculations for the Products of
Combustion 67
VI
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TABLES
1 Design Characteristics Per Combustion Unit 13
2 Sampling Schedule 17
3 Solid Waste Separation Categories 19
k Solid Waste Composition 28
5 Proximate Analyses of Solid Waste 29
6 Ultimate Analyses of Solid Waste 30
7 Residue Composition 31
8 Proximate Analyses of Residue ..... 32
9 Ultimate Analyses of Residue 33
10 Plant Efficiency 33
11 Average Chemical Characteristics of Wastewater 35
12 Average Solids Concentration of Wastewater 36
13 Stack Test Conditions 38
1** Summary of Particulate Emissions 39
15 Annual Cost Analyses k]
16 Cost of Repairs and Maintenance k2
17 Allocations for Repairs and Maintenance k2
18 Operating Cost by Cost Centers ^3
19 Projected Annual Cost at Design Capacity hk
20 Bacteriological Data 45
21 Col i form Data 46
A-l Proximate Analyses of the Combustible Portion
of the Solid Waste Samples 57
A-2 Conversion of the Combustible and Noncombustible
Data to a Dry Basis 58
VI I
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B-l Proximate Analyses of the Unburned Combustibles
and Fines
B-2 Conversion of the Residue Data to a Dry Basis ........ &3
D- 1 Determination of Combustion Products ............ 68
D-2 Determination of Theoretical Combustion Products ...... 70
D-3 Determination of Combustion Products for Test No. 2 ..... 72
FIGURES
1 Schematic of the DeKalb County Incinerator ......... 10
2 DeKalb County Incinerator Plant Site ............ 11
3 Flow Diagram of the DeKalb County Incinerator ....... 18
VI I I
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A REPORT ON THE DEKALB COUNTY INCINERATOR STUDY
On October 28, 1968, the DeKalb County, Georgia, Department of
Public Health, requested assistance from the Bureau of Solid Waste
Management in solving the problem of excess particulate emissions
from the DeKalb County incinerator. A field study of the incinerator
was conducted from December 11 to 13, 1968, to determine the potential
level of pollution resulting from the solid, liquid, and gaseous
effluents from the incinerator. The results of this study will enable
the County, through the use of a consultant, to determine what
modifications to the plant and/or operation will be necessary to
achieve an acceptable quality of operation.
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REPORT SUMMARY
The DeKalb County incinerator is a rotary kiln incinerator with
two identical combustion units, each having a design capacity of 300
tons per 2k hr. Inclined reciprocating grates are used in the drying
and ignition chambers. Further combustion is achieved in the kiln and
mixing chamber. The combustion products from each furnace pass through
separate water scrubbers and are discharged to the atmosphere through
a common stack. The residue drops from the kiln into the quench tank
where a drag conveyor removes the residue and discharges it into a
residue truck for removal to a land disposal operation. The wastewater
from the scrubber and quench tank flows through a sedimentation basin
and is discharged to a small watercourse.
Soli d Waste
The principal portion of the combustibles was composed of 60.6
percent paper products and 18.3 percent food wastes. The major portion
of the noncombustibles was composed of 8.5 percent metals and 5-^
percent glass and ceramics. The bulked density ranged from 95 to 190
1b per cu yd and averaged 1^5 lb per cu yd. During the study period,
the waste received by the plant had an average moisture content (as
sampled) of 21.0 percent, a volatile content (dry) of 77-3 percent,
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an ash content (dry) of 22.7 percent, and a heat content (as sampled)
of 5,530 Btu per Ib.
Res i due
The fines averaged 79-^ percent. This can be attributed to a size
reduction of the residue as a result of the tumbling action occurring in
the rotary kiln. The unburned combustibles content averaged 0.7 percent,
the metals averaged 16.8 percent, and the glass and rocks averaged 3-1
percent. The density of the noncompacted, water-saturated residue
ranged from 1,^30 to 1,885 Ib per cu yd and averaged 1,615 Ib per cu
yd. The residue had an average moisture content (as sampled) of 2^.8
percent, a volatile content (dry) of 7-3 percent, an ash content (dry)
of 92.7 percent, and a heat content (dry) of 9^5 Btu per Ib.
Plant Efficiency
The plant achieved an overall weight reduction of approximately
72 percent, a volatile' reduction of approximately 97 percent, a volume
reduction of approximately 97 percent, and released approximately 96
percent of the available heat.
Process Waters
During the study the process wastewaters were not measured
quantitatively. However, past records showed that the plant consumption
averaged 936,100 gal per day or 2,095 gal per ton of solid waste
processed.
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The scrubber water had a temperature of 82 F, and the pH ranged
from 3-0 to 5-0. The alkalinity was 30 mg per liter, the chloride
content was 185 mg per liter, the hardness was 185 mg per liter, and
the phosphate content was 8.8 mg per liter. The total solids
concentration was 610 mg per liter, of which 14.8 percent was
suspended solids and 85.2 percent was dissolved solids.
After the scrubber water was added to the quench tank and the
quenched residue was removed, this wastewater had a temperature of
68 F, and the pH ranged from 5-4 to 7-1- The hardness concentration
remained nearly the same, but the alkalinity increased to 145 mg per
liter, the chloride content decreased to 100 mg per liter, and the
phosphate concentration increased to 13-8 mg per liter. The quench
water contained 1,120 mg per liter of total solids, of which 67-9
percent were suspended solids and 32.1 percent were dissolved solids.
The lagoon effluent had a temperature of 65 F, and the pH ranged
from 5.8 to 7.9. The alkalinity, chloride, and hardness concentrations
remained nearly the same, but the phosphate concentration decreased to
9.3 mg per liter. The total solids concentration was 900 mg per liter,
of which 63.9 percent were suspended and 36.1 percent were dissolved.
Because the solids were not continuously removed, the lagoon was full
of solids, and the total solids concentration was reduced only 19-6
percent by removing 2^.3 percent of the suspended solids.
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Burning Rate
During the study, the plant's burning rate was 35^ tons per 2k hr
with essentially one furnace operating (the second furnace was operated
for 19 hr only), which meant that the furnaces were operating at 107
percent of available design capacity. During the previous year, the
burning rate was 575 tons per 2k hr, which meant that the plant was
then operating at 9& percent of plant design capacity.
Particulate Emissions
The calculated gas concentration averaged 3-9 percent carbon
dioxide, 15-9 percent oxygen, and 80.2 percent nitrogen. The excess
air averaged 320 percent. The measured particulate emissions averaged
0.72 gr per scf (grains per standard cubic foot) corrected to 12
percent carbon dioxide, 1.18 Ib per 1,000 Ib of dry flue gas corrected
to 50 percent excess air, 167 Ib per hour, and 12.5 Ib per ton of
waste charged. These values are within ± 20 percent of the true
emission rates (see RESULTS).
Economic Analyses
Based upon the costs from the last fiscal year and an average
burning rate of 575 tons per 2k hr, the total annual cost was $558,092,
or $3.46 per ton, excluding revenue from private collectors. The
direct labor cost was 29-7 percent of the total cost. The operating
cost was 72.1 percent of the annual cost and the financing and
ownership costs were 27-9 percent.
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When the operating cost is based on cost centers, 30 percent was
spent in receiving, 3^ percent was spent in volume reduction, and 36
percent was spent in effluent treatment.
Bacteriological Analyses
The solid waste averaged 40 x 105 bacteria per gram and the residue
averaged 27 x 102 per gram. Thus the average total bacteria count was
reduced by a magnitude of 1,500. Aerobic spores were reduced by a
magnitude of 2,500 and anaerobic spores by a magnitude of 1,500. The
density of total coliforms and fecal coliforms isolated from the solid
waste was 33-4 x 104 per gram and 14.7 x 103 per gram, respectively.
Coliforms were also recovered from one sample of the quench water, but
there were no isolations from the residue, stack gas, fly ash, and
tapwater samples. Salmonella were not isolated from any source.
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FACILITY DESCRIPTION
The DeKalb County Sanitation Department operates two landfills and
one incinerator for all of the solid waste collected within Dekalb
County, excluding metropolitan Atlanta. The county incinerator is
centrally located on the public service area property adjacent to Memor-
ial Drive and Interstate 285, and is surrounded by land that is zoned
residential. The architectural design of the plant, the sedimentation
lagoon, and the nearness of a land disposal operation do not present an
attractive appearance.
The plant is of rotary kiln design with a design capacity of 600
tons per day. The incinerator was designed by International Incinerator,
Inc." and completed in November 1963- The plant has two continuous-feed
furnaces with a common stack. Each combustion unit consists of three
sections of inclined reciprocating grates (two drying grates and one
ignition grate), a rotary kiln, a gas-mixing chamber, and a water
scrubber (Figures 1 and 2).
Solid Waste Handling
Solid waste is weighed as it enters the plant and is accepted
throughout the workweek from commercial, industrial, and municipal
"Mention of commercial products does not imply endorsement by the
U.S. Government.
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sources. All incoming trucks are weighed continuously to provide a
weight record of the solid waste. A 30-ton Fairbanks-Morse automatic
scale located at the front of the building is used to weigh the
i ncoming trucks.
The storage pit is approximately 27 ft deep, 25i ft wide, and 962
ft long and has a capacity of 2,435 cu yd when filled to the level of
the tipping floor. Water sprays and ventilators are available for
controlling airborne dust generated within the storage pit during
dumping. Seven trucks can be accommodated at one time.
Two P & H 5"ton-capacity cranes with 3~cu-yd buckets are used to
charge the hoppers. The enclosed cab is mounted on the crane and
contains air-conditioning and heating systems.
Combust!on Uni t
Solid waste is fed to each furnace through a hopper having a cross
section of H by 8 ft and a depth of 19 ft. The hoppers are lined with
heavy-duty refractories.
Each combustion unit (Table 1) was designed to burn 300 tons of
solid waste per day. Each contains two sections of inclined reciprocating
drying grates and one section of inclined reciprocating ignition grates.
Siftings that fall through the drying grates are moved by an auger to
the ignition grates. Siftings from the ignition grates are also moved
by an auger to the qurnch tank. Suspended wall" were used to construct
the furnaces .
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TABLE 1
DESIGN CHARACTERISTICS PER COMBUSTION UNIT
Unit and characteristic
Speci fi cat ions
Drying grates:
Number 2
Type Reciprocating
Expected grate life li yr
Area 114 sq ft
Volume above grates 1,2kO cu ft
Drop distance between sections 10i in.
Drop distance to ignition grate 6 ft
Type of refractory High-duty
Expected refractory life 5 yr
Ign i tion grate:
Number 1
Type Reciprocating
Expected life H yr
Area 130 sq ft
Volume above grate 1,700 cu ft
Stroke k? in.
Drop distance to ki In k ft
Type of refractory Super-duty
Expected refractory life 5 yr
Kiln:
Internal diameter 10 ft 10 in.
Length 30 ft
Volume 2,760 cu ft
Type of refractory (a) First 15 ft--high-duty
(b) Last 15 ft--70% alumina
Expected refractory life (a) First 10 ft--3 yr
(b) Second 10 ft--li yr
(c) Third 10 ft--6-ll months
Slope i in. per ft
Gas bypass duct:
Volume 930 cu ft
Type of refractory Super-duty
Mixing chamber:
Volume 3,000 cu ft
Type of refractory Super-duty
Scrubber:
Type of refractory Super-duty
Expected refractory life 3 yr
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Each furnace has a forced-draft fan rated at 25,000 cu ft per min
at 10 in. of water static pressure. This fan supplies both the overfire
and underfire air to the ignition grate. The overfire air enters the
furnace over the ignition grates through ducts in the wall. The
underfire air enters the furnace through the ignition grates from a
plenum chamber below the grates. Manually operated dampers control
the distribution of the air. Past operation has relied primarily on
underfire air with occasional use of overfire air.
Approximately 35 percent of the hot gases bypass the furnace by
flowing from the ignition chamber over the incoming waste for drying.
The gases then flow through a bypass duct located above the drying
grate to the mixing chamber where they combine with the remaining
combustion gases (Figure l).
The common stack provides the natural draft required to remove the
combustion products from both furnaces. The stack is 200 ft high and
has an inside diameter of 16 2/3 ft at the sampling ports. It has a
30-ft target wall lined with high-duty fireclay brick, and the remainder
of the stack is lined with intermediate-duty fireclay brick. Guillotine
dampers located after each scrubber are used to control the natural
draft.
Residue Disposal
After passing through the kiln, the residue falls into one of the
two quench tanks. A gate directs the residue into the desired tank.
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A drag conveyor removes the residue from the quench tank to the residue
hopper. Three trucks, each with a capacity of 5 cu yd, are used to haul
the residue to a disposal site located i mile from the incinerator.
The residue is not normally weighed as it leaves the plant.
Air Pollution Control
A water scrubber containing two banks of sprays with two partial
baffle walls between them is used to reduce the fly ash emissions
(Figure 1). Each spray bank contains 5 horizontal water lines. Each
water line contains 11 holes 1/8 in. in diameter. Thus the water
scrubber contains 110 water sprays that spray downward at a 45° angle.
A layer of water is impounded on the floor of the scrubber by a standpipe,
Overflow through this standpipe is continuously discharged to the quench
tank. Every 4 hours, the fly ash entrained in this pool of water is
sluiced to the quench tank.
Instrumentat ion
An instrument panel is located on the main furnace floor between
the two furnaces. Instruments included are draft gauges, temperature
recorders, grate speed controls, and kiln speed controls. The
instrument readings are recorded hourly in a daily operation log.
The total draft supplied by the forced-draft fan, the draft above the
ignition grates, the draft in the mixing chamber, the draft in the
scrubber, and the natural draft provided by the stack are monitored.
15
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Temperatures are recorded from thermocouples located above the drying
grates, above the ignition grate, in the mixing chamber, and at the
base of the stack.
Plant Operation During Study
After 19 hr of operation on Monday of the study week, a refractory
failure occurred that required one of the furnaces to be removed from
operation. Because of the small capacity of the storage pit, a backlog
of solid waste accumulated.
During the study period the residue was weighed as it left the
plant.
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SAMPLING AND TESTING PROCEDURES
This section discusses the methods used to collect and analyze the
following samples: (1) solid waste, (2) residue, (3) stack particulate
emissions, and (4) process water. The sample preparation for the
bacteriological analysis is also described. The sampling locations
(Figure 3) of the solid, liquid, and gaseous products of the incinerator
were based on their flow systems and ease of sampling.
A field study of the DeKalb County incinerator was conducted from
December 11 to 13, 1968, to determine the characteristics of its
operation. Samples were collected according to the schedule in Table
2.
TABLE 2
SAMPLING SCHEDULE
Source
Stack particulates
Sol i d waste*
Resi due"f
Process watert
Wednesday
(12-11-68)
none
1,2
none
none
Sample number
Thursday
(12-12-68)
1,2,3
3,^,5,6,7,8
1,2
1,2,3
Fri day
(12-13-68)
4
none
3,4
k
Even-numbered samples returned to laboratory for analyses.
"'"All samples returned to laboratory for analyses.
1 sources were sampled.
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SOURCE
FLOW SAMPLING POINT
SOLID WASTE, RESIDUE, )'
AND FLY ASH
PROCESS WATER ^
GASES AND PARTICULATES
Figure 3. Flow diagram of the DeKalb County incinerator.
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Sol id Waste
The amount burned during the study was calculated from the weight
records of the solid waste delivered to the plant an an estimate of the
amount of solid waste in the storage pit before and after the test
period. The burning rate was determined by dividing this amount by
the hours of operation during the week.
A total of eight samples, representative of the wastes being
burned, were obtained from the storage pit. These samples were spread
on a drop cloth and hand-sorted into nine categories (Table 3). Each
category was weighed and the percent by weight was determined for each
category on an "as received" basis. Using these percentages, 10- to
15~lb samples were reconstituted from the combustible portion for
TABLE 3
SOLID WASTE SEPARATION CATEGORIES
Combustibles" Noncombustibles
Food waste Metal products
Paper products Glass and ceramics
Plastics, rubber, and Ash, rocks, and dirt
leather
Wood
Garden waste
Textiles
"Determined by physical separation.
19
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laboratory analyses. To prevent moisture loss, each of those samples
was placed in two plastic bags, one inside the other, and each bag
was knotted separately.
Before separation, the bulked density of the solid waste sample
was obtained by filling a 0.1 cu yd container and determining the net
weight. No effort was made to compact the wastes during placement in
the container.
At the laboratory, the combustible portion of the solid waste
sample was processed in a hammermill to reduce the maximum particle
size to 1 in. The ground product was spread on a plastic sheet and
thoroughly mixed. The sample was then successively mixed and quartered,
and alternate quarters were discarded. This process was repeated until
a sample size of 3 to k Ib was obtained.
A 100-gram portion was dried at 70 to 75 C to constant weight to
determine the moisture content.1 The sample was then ground in a Wiley
mill until it would pass through a 2-mm mesh sieve. The volatile*
and ash fractions1 and the heat content2 were then determined. Ultimate
analyses^ for carbon, hydrogen, oxygen, nitrogen, sulfur, and chlorine
were performed on the ground sample. The sample was also analyzed for
ash.
Res i due
Samples were collected from the residue conveyor after the stack
test, spread on a drop cloth, and hand-sorted into four categories.
'Material determined by a laboratory analysis.
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These categories were the unburned combustibles, fines, metals, and
glass and rocks. The fines are the unidentified materials that pass
through a j-in.-mesh screen and do include metal and combustible
materials. After separation, each category was weighed and the percent
by weight on a wet basis for each category was determined. The fines
and unburned combustibles were individually sealed in plastic bags to
preserve the moisture content and were returned to the laboratory for
analyses. The remaining categories were discarded.
The bulked density of the residue was obtained by filling a 0.03"
cu-yd container with the samples obtained from the drag conveyor and
determining the net weight. No effort was made to compact the residue
during placement in the container.
At the laboratory, the fines and unburned combustibles were
processed in the same fashion as the solid waste samples, but with
the following exceptions: a 100-gram portion was dried at 100 to
105 C to constant weight to determine the moisture content, and benzoic
acid was used as a combustion aid in the calorimeter to determine the
heat content. Ultimate analyses were also performed on the ground
sample.
Sample No. 2 was not separated and was returned to the laboratory
intact for moisture determination only.
Particulate Emissions
On Monday, the equipment was assembled and the preliminary
measurements were made on Wednesday to determine the moisture content,
21
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carbon dioxide content, and velocity of the stack gases. Three
particulate tests were conducted on Thursday and one on Friday. The
sampling train and the sampling and analytical procedures used are
described in "Specifications for Incinerator Testing at Federal
Facilities."4
The sampling ports were located 66 2/3 ft above the stack foundation
and approximately 180° apart. Samples were taken from the sampling
ports utilizing a 24-point traverse inside the stack. The sampling
ports were located 3 diameters from the top of the stack inlet and 8
diameters from the stack exit. Velocity head ranged from 0.01 to
0.08 in. of water. A 3/8-in. nozzle was used on the particulate
sampling probe. Initially the sampling time was k min at each point.
The sampling time was increased to 6 min for the last three tests.
During the test, whenever excessive accumulations of particulate
on the filters hindered isokinetic sampling, the filters were replaced
and the test continued.
Process Waters
Each source of process water was sampled to determine its
characteristics. These sources were the incoming water (municipal
water), scrubber water, scrubber sluicing water, quench water
(containing scrubber water), and the plant's final effluent after-
passing through a lagoon.
Two grab samples from each source, except the scrubber sluicing
water, were collected during each stack test. A 1-liter composite
22
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sample based on equal portions was made from the grab samples for
each source for each stack test, except for the scrubber sluicing
water where only grab samples were obtained. These samples were
shipped to the laboratory to be analyzed for solids, alkalinity,5
chloride,5 hardness, sulfate,'' phosphate,r'F' and conductivity.5 The
pH and temperature of each sample was determined in the field. A
Corning pH meter, Model No. 7, was used.7
Economi cs
The cost data were obtained by checking all cost records kept by
the plant and any administrative group keeping pertinent records. In
addition, the personnel who maintained the cost records were questioned
to verify and incorporate correctly the cost data to fit the Bureau's
cost-accounting scheme.
Bacteriological Analyses
The solid waste, residue, quench water, stack gases, fly ash, and
tapwater were sampled and analyzed for total bacterial count, heat-
resistant spores, coliforms, salmonella, and selected respiratory
pathogens.
A 200-g sample of solid waste was homogenized for 15 sec in a
Waring Blendor containing 1,800 ml of phosphate-buffered water. Serial
tenfold dilutions in sterile phosphate-buffered water were made through
10~7 after homogenization. For the solid waste, 0.1-ml aliquots from a
dilution of 10" to 10~7 (yielding 1 log higher dilution) were pipetted
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into petri dishes for total bacterial count5 and onto prepared blood
agar plates for the propogation of fastidious organisms. Ten-m]
aliquots of each dilution were then transferred to tubes and heated
in a waterbath at 80 C for 15 min for the testing of sporeformers.'3
In addition to aerobic spores, anaerobic spores were tested by use of
anaerobic jars. One-mi aliquots from the initial dilutions used for
total count and pathogen isolation were filtered through Millipore
membranes for the quantitation of total and fecal coliforms.5 The
same procedures were used for the residue, except that the dilutions
were pipetted from 10"1 through 10~3.
In order to isolate salmonella,8>g 30 grams of material were
placed into each of two different enrichment media and incubated at:
41 C for 18 hr. After incubation, the enrichments were streaked onto
selective enteric plates and also incubated at k] C for 18 hr. Suspected
salmonella colonies were tested for biochemical and serological
reactions.10 Selective cultures were sent to the National Communicable
Disease Center, Atlanta, for serological typing of the salmonella
species.
The methods used for analyzing the quench water were similar to
those used for the solid waste. For the analyses of total bacterial
count, sporeformers, fastidious pathogens, and coliforms, the dilutions
ranged from 10° to 10~6. Thirty-mi aliquots of quench water were
inoculated into each enteric enrichment media for salmonella. The
tapwater was tested in a similar manner.
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One gram of fly ash was placed into 9 ml of buffered water from
which 1-ml and 0.1-ml aliquots were tested for total bacterial count,
sporeformers, and respiratory pathogens.
The stack sampling device was calibrated to pull 0.62 cu ft per
minute. The sampling time was 5 min for the first sample and 10 min
for the second. The stack gases were forced through 300 ml of buffered
water. After sampling, 100 ml of the inoculated buffered water were
filtered through a membrane filter for total bacterial count. One-mi
amounts were tested for sporeformers and pathogens.
25
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RESULTS
This section presents the data obtained from the analyses of
samples taken during the field study of the DeKalb County incinerator.
Sol id Waste
The physical composition data (Table 4) was calculated on an "as
recei ved" bas i s.
The densities of the uncompacted solid waste samples were calculated
on a wet basis as sampled from the storage pit. The values for samples
3 through 8 are 1^0, 95, HO, 170, 155, and 190 Ib per cu yd, respectively.
The average density was 1^5 Ib per cu yd.
For the proximate analyses of the solid waste (Table 5), the ash
and volatile fractions were calculated on a dry basis, and the heat
content was calculated on an "as received" basis. Only the combustible
portion was analyzed, and the results were calculated for the complete
sample by assuming that the noncombustibles contained no moisture, no
heat, and were considered as "ash." Example calculations are given in
Appendix A.
Because the proximate and ultimate analysis data for solid waste
sample No. 2 appeared significantly different when compared to the
other data, these data were not used in calculating the average values.
27
-------
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TABLE 5
PROXIMATE ANALYSES OF SOLID WASTE
Sample
number
2*
k
6
8
Average
Moisture,
as sampled
(%)
26.7
21.1
20.2
21.8
21.0
Volati les,
dry
(*)
51.8
81.0
79.9
71.1
77-3
Ash,
dry
(*)
48.2
19-0
20.1
28.9
22.7
Heat,
as sampled
(Btu/lb)
3,910
5,730
5,700
5,160
5,530
-The data from this sample were not used when determining the
average values.
The results from the ultimate analyses of the solid wastes (Table
6) were calculated on an "as received" basis. It was assumed that
each sample contained only those elements shown, and the results were
accordingly adjusted on a weight basis to 100 percent.
Res idue
The residue separation data (Table 7) were calculated on an "as
sampled" basis.
The densities of the uncompacted residue samples were calculated on
a wet basis as sampled from the conveyor. The densities of samples 1,
3, and k were 1,530, 1,885, and 1,^30 Ib per cu yd, respectively. The
average density was 1,615 Ib per cu yd.
29
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The proximate analyses data for the complete sample (Table 8)
were calculated from the analyses of the fines and unburned combustibles.
The moisture content is only representative of the sampling location,
which was the residue conveyor. The percent of vofatiles and heat content
were calculated on a dry basis by assuming that the glass and metals
contained no moisture, no heat, and were considered as "ash." Sample
No. 2 was not separated and was analyzed only for moisture. Example
calculations are presented in Appendix B.
TABLE 8
PROXIMATE ANALYSES OF RESIDUE
Sample
number
1
OJ-
3
4
Average
As sampled
Moisture (%)
37.4
20.8
26.3
14.9
2k. 8
Component
Volatiles (%)
8.5
3.4
10.0
7.3
Dry
Ash (%)
91.5
96.6
90.0
92.7
Heat (Btu/lb)
1,335
570
930
945
-This sample was analyzed for moisture only.
The data from the ultimate analyses of the residue (Table 9) were
adjusted to a dry basis by assuming that each sample contained only the
seven constituents reported, and the results were adjusted accordingly
on a weight basis to 100 percent.
32
-------
TABLE 9
ULTIMATE ANALYSES OF RESIDUE
(Percent)
Sample
number
1
3
k
Average
1 nerts
88.2
9^.4
91.8
91.5
Carbon
11.3
5.0
7.8
8.0
Hydrogen
0.2
0.3
0.1
0.2
Oxygen
0.0
0.0
0.0
0.0
Sulfur
0.2
0.2
0.2
0.2
Chlorine
0.0
0.0
0.0
0.0
N i t rogen
0.1
0.1
0.1
0.1
Total
100.0
100.0
100.0
100.0
Plant Efficiency
An indication of the plant's performance is obtained by calculating
the percent of weight reduction, volatile reduction, heat released, and
volume reduction (Table 10). These calculations are shown in Appendix C.
TABLE 10
PLANT EFFICIENCY
Efficiency Percent
Weight reduction 72
Volatile reduction 97
Heat released 96
Volume reduction 97
Samples of the particulates and wastewater solids were not analyzed
for ash, volatiles, or heat content. The wastewater flow also was not
33
-------
measured. Because these values were not used in the plant efficiency
calculations, the efficiencies shown are slightly higher than they
would have been if these values had been included.
The dry weights of the solid waste, residue, and particulates were
used to calculate the percent of weight reduction. The percent of
volatile reduction was also calculated on a dry basis by using the solid
waste and residue data. The percent of heat released was calculated
with the residue data on a dry basis, and the solid waste data on an
"as received" basis. The percent of volume reduction was calculated
from the wet density values and the total weights of solid waste and
res i due.
Process Waters
It was impossible to obtain a sample of the quench water because
the scrubber water was continuously discharged into the quench tank.
The data (Tables 11 and 12) for the quench water were obtained from the
analyses of this mixture of scrubber water and quench water. This
mixture was the final effluent from the combustion process. After
removal of the heavy solids in a lagoon, this process water was
discharged to a small watercourse.
Instrument Readings
During the stack tests, the instrument panel was monitored to
provide information about the plant's operation. Temperatures throughout
the combustion unit were monitored at several points. The preheated
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air used to dry the solid waste averaged 250 F. The average operating
temperature in the ignition chamber and mixing chamber was 1,865 F and
1,885 F, respectively. The temperature in the scrubber after the sprays
averaged 485 F. Ambient air flowing through the furnace down for
repairs diluted the combustion products from the furnace in operation.
Because this dilution occurred after the scrubber, the temperature of
the gases measured at the stack sampling location was reduced to
365 F.
Burning Rate
During the study week, 2,300 tons of solid waste were processed
in 172 hr of operation and 660 tons of wet residue remained. The
average daily burning rate of the plant, assuming a 6£ day operation,
was 354 tons per 2k hr, 14.8 tons per hr, or 59 percent of plant
design capacity. Because one furnace was operated 153 hr and the
other only 19 hr during the study week, the furnace burning rate was
320 tons per 2k hr, 13.4 tons per hr, or 107 percent of the available
furnace design capacity. During the previous fiscal year, the plant
burned 161,166 tons during 280 operating days for an average of 575
tons per 24 hr, 24.0 tons per hr, or 96 percent of the plant design
capacity. Because only one furnace was in operation during the stack
tests, a burning rate of 13-4 tons per hour was used in all calculations.
Particulate Emissions
During the stack tests, the Orsat apparatus malfunctioned and
could not be repaired before completion of the study. Analyses of
.37
-------
the stack gases, therefore, could not be made. Ultimate analyses were
performed on the solid waste and residue samples, and the gaseous
products of combustion were calculated. From these combustion products,
the concentrations of the major gases in the stack were calculated by
assuming a 20-percent reduction11 of carbon dioxide in the water
scrubber. An example calculation is presented in Appendix D. These
calculated products of combustion (Table 13) were then used to adjust
particulate emission concentrations (Table 1*0 to standard conditions.
The particulate emissions include the weight of material remaining
after evaporation of the impinger water.
TABLE 13
STACK TEST CONDITIONS
Calculated stack gas composition
Test
(
(
(
(
No. and date
1
12-12-68)
2
12-12-68)
3
12-12-68)
4
12-13-68)
Average
Length
of test
(min) LU2
97 5.0
144 3-7
136 3.2
1^4 3.7
3.9
(percent)
o2 co
14.5 0.0
16.2 0.0
16.8 0.0
16.2 0.0
15.9 0.0
N2
80.5
80.1
80.0
80.1
80.2
Excess
ai r
215
330
390
325
320
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The flow rates of the stack gases measured during the study when
one furnace was inoperative were, comparable to those expected when
both furnaces were operating, which means that ambient air was being
pulled through the inoperative furnace. It was not possible to isolate
this inoperative unit. The ambient air from the inoperative furnace
and the products of combustion from the operative furnace were mixed
at the base of the stack. Thus, the calculated products of combustion
are representative of the gases in the stack, but not of the gases in
the operative furnace. This decreased the carbon dioxide concentration,
increased the excess air, and diluted the particulate emissions before
correction to standard conditions.
In addition to the ambient air being pulled through the inoperative
furnace, some particulates were entrained in this air from the rebricking
and cleaning operations. it was not possible to measure the quantity of
entrained particulates from the inoperative furnace. However, in our
opinion, the measured and reported particulate emissions are within ±
20 percent of values representative of the operating furnace.
The National Air Pollution Control Administration (NAPCA) indicated
that approximately 20 percent of the carbon dioxide is removed when
combustion gases are passed through water scrubbers.11 Taking this
removal into account results in a higher adjusted grain loading than
would have occurred if all the carbon dioxide had passed through the
scrubber (0.72 gr/scf at 12 percent C0? with C0? removal versus 0.57
without CO removal). The NAPCA recommended that no adjustment be
allowed for this reduction in carbon dioxide content.
-------
Economic Analyses
The annual cost of the incinerator (Table 15) was based on a
1-year time period from July 196? to July 1968. The costs are shown
as operating costs and financing and ownership costs in terms of
actual cost, cost per ton (based on 575 tons per 2k hr), and percent
of annual cost.
The financing and ownership costs were based on a capital cost of
$2.4 million and a plant life of 30 years. The plant depreciation was
calculated on a straight-line basis by dividing the capital cost by
the plant life. Financing was accomplished by issuing a 30-year bond
at an interest rate of 3-2 percent. The cost per ton was based on a
yearly tonnage of 161,166 tons processed in 280 operating days, or 575
tons per 2k hr.
TABLE 15
ANNUAL COST ANALYSES
Item Cost C°St Percent of
per ton annual cost
Operating costs:
Direct labor and fringe benefits $165,684 $1.03 29.7
Utilities (gas, electric,
sewage, etc.) 67,632 0.42 12.1
Parts and supplies 51,540 0.32 9.2
Vehicle operating expenses 9,600 0.06 1.7
External repair charges 12,758 0.08 2.3
Disposal charges 10,364 0.06 1.9
Overhead 84,674 0.52 15.2
Total 402,252 2.49 72.1
Financing and ownership costs:
Plant depreciation 80,000 0.50 14.3
Interest 75,840 0.47 13.6
Total 155,840 0.97 27-9
Total annual cost 558,092 3-46 100.0
-------
Several items in the annual cost analyses (Table 15) need further
explanation. The direct labor cost includes only the salaries of the
30 employees used in the operation of the incinerator. The salaries
of the remaining nine employees used in management and plant site
improvement are shown in the overhead. Because the plant was built
on land previously owned by the county and no additional expenses for
land were required, the cost of the land is not included. Also excluded
is the revenue received from private contractors who dumped waste at
the incinerator. They were charged $1.00 per ton; thus the incinerator
received a revenue of $55,965.
The cost of repairs and maintenance and its allocation to the
cost centers are calculated in Tables 16 and 17.
TABLE 16
COST OF REPAIRS AND MAINTENANCE
Item Cost
Labor $31,679
Parts 51,5^0
External charges 12,758
Overhead 16,189
Total 112,166
TABLE 17
ALLOCATIONS FOR REPAIRS AND MAINTENANCE
Cost center Allocation Percent of total
Receiving $17,960 16.0
Volume reduction 77,804 69.1*
Effluent treatment 16,402 14..6
Total 112,166 100.0
-------
The annual operating cost (Table 18) was allocated to the following
cost centers: receiving, which includes items associated with the
storage pit, crane, and scale operations; volume reduction, which
includes items associated with the furnace operation; and effluent
treatment, which includes items associated with the residue disposal,
air pollution control, and wastewater treatment operations. Allocation
of the operating costs into cost centers was achieved through the use
of physical factors such as the number of people involved, power
requirements, and the time and material used in each cost center.
TABLE 18
OPERATING COST BY COST CENTERS
Cost center
Receiving:
Direct labor
Uti 1 ities
Vehicle operating expenses
Repairs and maintenance
Overhead
Total
Volume reduction:
Direct labor
Uti 1 ities
Repairs and maintenance
Overhead
Total
Effluent treatment:
Direct labor
Uti 1 ities
Vehicle operating expenses
Disposal charges
Repairs and maintenance
Overhead
Total
Total operating cost
Operati ng
cost
$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
Percent
of total
operating cost
14.7
3.2
0.0
4.5
7.5
29.9
8.5
2.1
19-3
4.3
34.2
10.1
11.6
2.4
2.6
4.1
5.1
35.9
100.0
Percent of
annual cost
10.7
2.3
0,r
3.*.
5.4
21.6
6.1
1.6
13.9
3.1
24.7
7.2
8.4
1.7
1.9
2.9
3-7
25.8
72.1
43
-------
The labor costs in the projected annual cost at design capacity
(Table 19) remain the same, because the plant is fully staffed. The
financing and ownership costs also remain the same, because the expected
plant life is 30 years. Again, the revenue from private contractors was
not included.
TABLE 19
PROJECTED ANNUAL COST AT DESIGN CAPACITY
1 tern
Operating cost:
Direct labor
Uti lities
Parts and suppl ies
Vehicle operating expenses
External repair charges
Disposal charges
Overhead
Total
Financing and ownership costs:
Plant depreciation
1 nterest
Total
Total projected annual cost
Cost
$165,686
70,499
53,725
10,007
13,298
10,803
84, 67k
408,692
80,000
75,8i»0
155,840
564,532
Cost
per ton
0.99
0.42
0.32
0.06
0.08
0.06
0.50
2.43
0.48
0.45
0.93
3-36
Percent
of projected
annual cost
29-3
12.5
9-5
1.8
2.4
1.9
15.0
72.4
14.2
13-4
27.6
100.0
Bacteriological Analyses
Samples of solid waste, residue, quench water, stack gases, and
fly ash were analyzed for total bacteria, sporeformers, coliforms,
salmonella, and selected respiratory organisms (Tables 20 and 21).
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-------
Other isolations from the solid waste samples were the Alkalescenes--
Dispar Group and staphylococcus aureus hemolytious. Alpha hemolytic
streptococcus was isolated from the stack gas sample.
The quench water and tapwater data are expressed as density per
100 ml of sample. When no colonies were isolated the densities were
expressed as less than 100 per 100 ml of sample.
The total bacterial count was done by the membrane-filter method,
and 100 ml of the inoculated buffered water sample were tested. When
equated to cubic feet of stack gas, the quantitative result is expressed
as equal to or less than 0.976 cu ft when the sampling time was 5 min.
A maximum of 1 ml of the buffered water sample could be tested by
use of the pour plate for the sporeformers. The quantitative value is
expressed as equal to or less than 97-6 per cu ft of stack gas when tl
sampling time was 5 min.
-------
-------
DISCUSSION
Last year the plant burned 65 percent of the solid waste collected
within DeKalb County, with the exception of metropolitan Atlanta. This
averaged 575 tons per 2k hr, which is 96 percent of the plant's design
capacity. With an average annual increase in tonnage of 6 percent, the
plant will reach design capacity during 1969.
The extremely small capacity of the storage pit (approximately 420
tons) does not allow sufficient time for normal repairs and maintenance
of the combustion units. For example, if a repair requires a unit to
be out of operation for a day, solid waste accumulates and overflows
the pit, thereby hindering dumping operations, adversely affecting the
appearance of the plant, and requiring extra manpower for cleanup
purposes. When this condition occurs, some of the solid waste is
diverted to the land disposal operations. However, insufficient
quantities of waste are diverted to alleviate this problem.
The particulate emissions to the atmosphere are high (0.72 gr per
scf of dry flue gas corrected to 12% C0_) when compared to existing
codes, such as the code for incinerators at Federal facilities (0.2 gr
per scf of dry flue gas corrected to 12% C0?) . To reduce these
emissions to meet such a code would require a more efficient particulate
collector and/or modifications to existing operational procedures.
-------
The concentrations of pollutants within the wastewater discharged
to the watercourse were high (total solids, 900 mg per liter and
suspended solids, 575 mg per liter). These conditions indicate that
the lagoon should be dredged periodically to increase the detention
time for efficient removal.
Complaints from the public about an incinerator can be caused by
a poor aesthetic appearance regardless of the quality of operation.
This facility presents an unattractive appearance because the dreclgings
from the lagoon are left beside the lagoon rather than removed from
the facility site. The unattractiveness of the facility is also caused
by equipment and replaced parts from the furnaces lying on the facility
grounds. In addition, when the pit overflows with waste, these wastes
spill on the tipping area, which is in public view.
-------
REFERENCES
American Public Works Association. Municipal refuse disposal. 2nd
ed. Chicago, Public Administration Service, 1966- Appendix A.
P. 375-399.
2. Parr Instrument Company. Operating the adiabatic calorimeter. I n
Oxygen bomb calorimetry and combustion methods. Technical Manual
No. 130. Moline, 111., 1966. p. 30-32.
3. Ultimate Analysis Procedures.
a. American Society for Testing Materials. Carbon and hydrogen. In
1958 Book of ASTM standards; including tentatives. pt. 8. D:r2~71-58,
sect. 38-^3. Philadelphia, 1959- p. 1016-1020.
b. American Society for Testing Materials. Sulfur by the bomb washing
method. In 1958 Book of ASTM standards; including tentatives. pt.
8. D-271-58, sect. 26. Philadelphia, 1959. P- 1011.
c. Association of Official Agricultural Chemists. Chlorine--official,
final action. J_n_ Official methods of analysis of the Association
of Official Agricultural Chemists. 10th ed. sect. 31.009. Wash-
ington, 1965. p. 523.
d. American Society for Testing Materials. Oxygen. In 1958 Book of
ASTM standards; including tentatives. pt. 8. D-271-58, sect. 50.
Philadelphia, 1959. p. 1023-
e. Association of Official Agricultural Chemists. Nitrogen. In Off i c i &i
methods of analysis of the Association of Official Agricultural
Chemists. 10th ed. sect. 2.0^2-2.049. Washington, 19&5- p. 15-17.
k. National Center for Air Pollution Control. Specifications for in-
cinerator testing at Federal facilities. Durham, N.C., U.S.
Department of Health, Education, and Welfare, Oct. 1967- 35 p.
5. American Public Health Association, American Water Works Association,
and Water Pollution Control Federation. Standard methods for the
examination of water and wastewater; including bottom sediments
and sludges. 12th ed. New York, American Public Health Associa-
tion, Inc., 1965. 769 p.
51
-------
6. Gales, M. E., Jr., E. C. Julian, and R. C. Kroner. Method for
quantitative determination of total phosphorus in water. Journal
American Water Works Association, 58(10):1363-!368, Oct. 1966.
D
7. Corning Glass Works. Corning model 7 pH meter instruction manual.
Corning, N.Y., 196*1. [7 p.]
8. Harvey, R. W. S., and T. H. Price. Elevated temperature incubation
of enrichment media for the isolation of salmonellas from heavily
contaminated materials. Journal of Hygiene, 66(3):377~38l , Sept.
1968.
9. Spino, D. F. Elevated-temperature technique for the isolation of
Salmonella from streams. Applied Microbiology, \k(k):591"596,
July 1966.
10. Hajna, A. A. "A proposed rapid method of differentiating and identi-
fying bacteria of the intestinal group in State public health
laboratories." Public Health Laboratory, 9(2):23-30, Mar. 1951.
11. Personal communications. W. A. Cote, National Center for Air Pollu-
tion Control, to National Center for Air Pollution Control, Nov. 13,
1967.
52
-------
ACKNOWLEDGMENTS
The excellent cooperation of the staff of the DeKalb County
incinerator made the successful completion of this study possible.
Special thanks are extended to Mr. James A. Nuckles, superintendent
of the DeKalb County incinerator, whose efforts were essential in
planning and conducting the study.
The laboratory assistance provided by the Georgia Institute of
Technology was greatly appreciated. Analytical support was provided
by the Division of Research and Development, Bureau of Solid Waste
Management.
Members of the field study team were as follows:
William C. Achinger Daniel Armstrong
James S. Bridges Hugh W. Connolly
Leland E. Daniels Truett V. DeGeare
Dennis A. Degner Jack DeMarco
John J. Giar Jeffrey L. Hahn
Tobias A. Hegdahl Billy P. Helms
Henry Johnson Albert E. O'Connor
Ronald A. Perkins Harvey W. Rogers
Donald F. Spino
53
-------
-------
APPENDICES
55
-------
-------
APPENDIX A
Example Calculations for the Ash, Volatile,
and Heat Content of the Solid Waste
Using the data from the laboratory analyses of solid waste sample
No. 4, these example calculations show the methods used to calculate
the moisture content, ash and volatile content, and the heat content of
the total sample. Data received from the analyses of the solid waste
samples returned to the laboratory are presented in Table A-l. The
volatile and ash fractions and the heat content are on a dry basis.
For these calculations, the assumptions were made that the noncombustibles
contained no moisture, no heat, and were considered as "ash."
TABLE A-l
PROXIMATE ANALYSES OF THE COMBUSTIBLE PORTION
OF THE SOLID WASTE SAMPLES
Sample
number
2*
k
6
8
Average
Moi sture
(*)
37.3
23-0
23.1
26.9
2**. 3
Volati les
(%)
84.5
90.2
94.7
93.8
92.9
Ash
(*)
15.5
9.8
5.3
6.2
7.1
Heat
(Btu/lb)
8,690
8,085
8,^50
8,705
8,1*15
"The data from this sample were not included when the average
values were determined (see RESULTS).
57
-------
The field separation determined a combustible content of 91.9
percent (Text Table 4) on a wet-weight basis. Because the moisture
in the total sample was assumed to be in the combustible portion
only, the percent of moisture in the total sample was calculated by
the following method:
Percent moisture in _ / Ib combust ibles I / 1b moisture \
total sample I Ib waste / I Ib combustibles/ loo-°
Percent moisture in
total sample = (0.919) (0.23) 100.0 = 21.1
(No. k)
Because the volatile and ash fractions are calculated on a dry
basis, the percent combustibles must be converted to a dry basis by
means of the following equation:
(Ib wet component minus Ib moisture in component \
dry sample wei ght I
component J~ '~ -'-* '
These calculations are summarized in Table A-2.
TABLE A-2
CONVERSION OF THE COMBUSTIBLE AND NONCOMBUSTIBLE
DATA TO A DRY BASIS
Component
Combust! b les
Noncombus t ib les
Total sample
Wet
we i ght
(Ib)
23k. Q
20.5
25^.5
Percent
by wet
wei ght
91.9
8.1
100.0
Mois
%
23.0
0.0*
21 .1
ture
Ib
53.8
0.0
53.8
Dry
wei ght
(Ib)
180.2
20.5
200.7
Percent
by dry
wei ght
89-3
70.2
100.0
"Assumed .
58
-------
The percent volatiles and ash may be calculated as follows:
Percent volat iles
in total sample
Percent volatiles
in total sample
(No. k)
Ib volatiles
Ib dry combustibles
Ib dry combustibles
Ib dry waste
= (0.902) (0.898) 100.0 = 81.0
100.0
Percent ash ,_.. , ^.,
. . , , 100.0 - percent volatiles
in total sample
Percent ash
in total sample = 100.0 - 81.0 = 19.0
(No. k)
The laboratory reports the heat content on a dry basis for the
combustibles only. Thus the moisture content and the noncombustibles
in the total sample must be accounted for when calculating the heat
content of the total sample on an "as received" basis.
Heat content of
total sample
Btu
Ib dry combustibles/
Percent noncombustibles
of total sample
1-
Tercent moisture
in total sample
100.0
100.0
Heat content of
total sample
(No. 4)
= (8,035)
100.0
Btu
Ib waste
)
59
-------
-------
APPENDIX B
Example Calculations for the Ash, Volatile,
and Heat Content of the Residue
Using the data from the laboratory analyses of residue sample
No. 1, these example calculations show the methods used to calculate
the moisture content, ash and volatile content, and the heat content
of the total sample. Table B-1 presents the laboratory data received
from the analyses of the portions of each residue sample returned to
the laboratory. For each sample, only the fines and unburned combustibles
were returned. The volatile and ash fractions and the heat content are
on a dry basis.
TABLE B-1
PROXIMATE ANALYSES OF THE UNBURNED COMBUSTIBLES AND FINES
Unburned combustibles
[ Moisture
number ,0/\
1 39.2
3 81.1
4 68.9
Average 63.!
Volati les
(*)
36.0
68.8
56.5
53.8
Ash
(%)
64.0
31.2
43.5
46.2
Heat
(Btu/lb)
3,775
8,200
7,395
6,455
Moi sture
(*)
^5.9
33.5
18.3
32.6
Fines
Volati les
(*)
11.6
4.7
7-7
8.0
Ash
(*)
88.4
95.3
92.3
92.0
Heat
(Btu/lb)
1,875
800
1,200
1,290
-------
The amount of fines and unburned combustibles found during the
field separation was 80.4 and 1.3 percent, respectively, on a wet-weight
basis. The assumptions were made that the glass and rocks and metals
contained no moisture, no heat, and were considered as "ash."
Because the moisture in the total sample was assumed to be in the
fines and unburned combustibles, the percent moisture in the total
sample is calculated by the following method:
Percent moisture
in total sample
/ Ib fines \ / Ib moisture\
^lb residue^ I Ib fines )
Ib unburned \ /
combustibles \ / Ib moisture
Ib residue | I Ib unburned
combust i bles
100.0
Percent moisture
in total sample = [(0.804)(0.*»59) + (0.013)(0.392)] 100.0
(No. 1)
Percent moisture
in total sample = 37» ^
(No. 1)
Because the remaining calculations are on a dry basis, the separation
data from Text Table 7 must be converted to a dry basis by the following
method:
Percent dry _/1b wet component minus Ib moisture in wet component
component \ total dry sample weight
These calculations are summarized in the following table:
62
-------
TABLE B-2
CONVERSION OF THE RESIDUE DATA TO A DRY BASIS
Wet .. . Dry Percent
_ . , . Moisture ' , ,
Component weight % rr weight by dry
(Ib) /0 lb (Ib) weight
Fines 63.8 45-9 29.3 34.5 69.6
Unburned combustibles 1.0 39.2 0.4 0.6 1.2
Glass and rocks 0.5 0.0* 0.0 0.5 1.0
Metal 14.0 0.0* 0.0 14.0 28.2
Total sample 79-3 37-4 29-7 49.6 100.0
'Assumed.
The percent volatiles and ash are calculated for the total sample
by the following method:
Percent volatiles
in total sample
/lb volat i les \ / lb dry fines \ + / lb volati les \
lib dry fines /lib dry residue) lib dry unburned combustibles/
Mb dry unburned combust ibles |
\ lb dry residue /
100.0
Percent volatiles
in total sample = [(0.116)(0.696) + (0.36)(0.012)] 100.0
(No. 1)
Percent volatiles
in total sample = 8.5
(No. 1)
Percent ash in ,nr. _ . , . .,
^ , , = 100.0 - percent volatiles
total sample ^
Percent ash in
total sample = 100.0 - 8.5 = 91.5
(No. 1)
63
-------
The heat content is calculated on a dry basis by the following
method:
Heat content
total sample
in = [/ Btu \ / 1b fines \
e \'k f'nes / lib residue/
+ / BU, \ /
lib unburned combustibles! I
1b unburned combustibles
Ib residue
Heat content in / R \
total sample = (1,875)(0.696) + (3,775)(0.012) = 1,335 L ^,du )
(No. 1) \ " /
-------
APPENDIX C
Plant Efficiency Calculations
These calculations show the methods used to determine the percent
of weight reduction, the percent of volatile reduction, the percent of
heat released, and the percent of volume reduction. The following data
are given:
Res i due:
660 tons (wet)
500 tons (dry)
2k.8 percent moisture
7-3 percent volatiles (dry)
3k5 Btu per Ib
1,615 Ib per cu yd
172 hr of burning time
Parti culates:
167 Ib per hr
Sol id waste:
2,300 tons (wet)
1,820 tons (dry)
21.0 percent moisture
77.3 percent volatiles (dry)
5,530 Btu per Ib
1^5 Ib per cu yd
Percent weight
reducti on
dry residue wt + dry particulate wt
dry sol id waste wt
Percent weight
reduction
dry wt of
wastewater solids*
dry sol i d waste wt
1-
)
/
100.0
Percent weight _ I,
reducti on
['
100.0
100.0 = 71.7
'Not measured.
-------
Percent volatile
reduct ion
(volatile
in resi
volatil
wt
due
volatile wt
parti culates
_
le wt in solid waste
in \
es* I
e /
Percent volat ile
reduct i on
Percent volatile
reduct i on
volatile wt in
' wastewater solids*
Ivolatile wt in solid waste
(0.073)(500) ]
(0.773)(1,820)J
)
100.0
1-
(TTW)
100.0 = 97.
Percent heat
re leased
1-
'heat content
L of res i due
wt of
res i due
wt of partic- heat content of
ulates- wastewater solids-
heat content of
parti culates*
wt of \
Percent heat
released
Percent heat
released
[heat content of wt of solii
^ solid waste waste
(945) (2,000) (500) "|
(5,530) (2,000) (2,300) |
45 x 108'
1-
soli ds-
100.0
100.0
"i / 9.45 * 1Q8\"
'" (254.4 x 10a )
100.0 = 96.3
Percent volume
reducti on
1-
(total wt of wet residue wt of participates*
density of wet residue density of particulates
total wt of solid waste'
recei ved"
wt of wastewater solids*
dens i ty of soli ds
)/ total
( "as
\ dens i
Percent volume
reduct i on
Percent volume
reduct i on
--Not measured.
1-
(660.8 x 2,000\ . / 2,300 * 2,OQO\
-T^T5 j ^ Ws )
I 817 \1
(31,7241 I
ty of solid waste
100.0
100.0 = 97.4
100.0
66
-------
APPENDIX D
Example Calculations for the Products of Combustion
At the sampling point, the products of combustion are influenced
by the burning rate, the elemental composition of the waste, the
products of combustion at stoichiometric conditions, and the excess
air. The calculations contained in this appendix show the method used
to determine the products of combustion. The first step was to
complete Table D-1 . Initially, the pounds of each element per pound
of waste, the burning rate of solid waste, the pounds of each element
per pound of residue, the amount of residue per hour, and the pounds
of oxygen required to burn a pound of each element were known. After
calculating the pounds per hour of each element fed to the furnace as
solid waste and the pounds per hour of each element remaining as
residue, the table was completed by calculating the weight consumed
of each element, the percent consumed, and the weight of the oxygen
required to consume the total weight of each element consumed. The
following calculations complete the determination of the combustion
products.
Theoretical Ib of 0 required for oxidation of carbon . . . 20,256
Theoretical Ib of CL required for oxidation of hydrogen . . 8,^32
Theoretical Ib of 0 required for oxidation of sulfur . . . 15
Theoretical Ib of () required per element 28,703
Lb of 0 available in waste 7,086
Theoretical Ib of 0 required 21,617
67
-------
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68
-------
1b 0? , = 21.6)7 =
Ib waste 26.8AO
Ib ai r 0.805 Ib QZ A 0.2315 Ib
Ib wfsste Ib waste ' Ib air ~ '
The volume of the theoretical combustion products per pound of
waste may be calculated by using the ideal gas law, which is
ii i 387m
Volume = ~r
n
The mass of each component per pound of waste may be calculated
as follows:
b air \ / ..
waste) %wt N2
= excess
mfO = I Percent carbon consumed \ /3-66 Ib COg produced \
2 = ^ 100 I \ Ib carbon )
/percent hydrogen \ / .
mn n fuel - I consumed _ _ I ( 8.9^t Ib H20 produced ) percent H?0 in fuel
2U ruei \ 100 /\ Ib hydrogen / ^^ TOO "
iu n . / Ib air 0.0263 Ib H?0\
H00 excess air = [ ,r - r - .. . - * I
^ y Ib waste Ib a i r /
These calculations are summarized in Table D-2.
-------
TABLE 0-2
DETERMINATION OF THEORETICAL COMBUSTION PRODUCTS
Theoretical combustion products m M V
m = (0.7685)(3-479) + 0.0048 2.678 28 37.019
2
m = (0.2837)(3.66) 1.038 44 9-133
LU2
mu ,,, fuel = (0.0346) (8.3k) +0.21 * * *
H2°
mH Q, air = (3.479)(0.0263) *
m = excess 0.000 32 0.000
Theoretical dry gas volume 46.152
"Not applicable.
. , _ 46.152 scf 26,840 1b waste hr
Theoret.cal Q= 1b waste h? £5"^
Theoretical Q. = 20,645 scf/min
Calculate combustion products for Stack Test No. 2 as follows:
Excess air (EA) = Actual Q minus Theoretical Q
EA = 88,878 - 20,645
EA = 68,233 scf/min
From the ideal gas law, 1 Ib of excess air occupies 13-33 scf,
70
-------
EA _ 68,233 _
~ ~
Ib EA
Ib waste
Ib EA
Ib waste
Poi-ror,i- FA 1
13.33 >'"J
/5,119 Ib EA\ / hr
y min 1 ^26,840 Ib waste
/Ib EA/lb waste \ ,nn n _ /ll
)/60 min
V hr
443\
* «^ 1 i D f\
=
At 328.9 percent excess air, the total amount of air is 428.9 percent,
The theoretical amount of oxygen and air used is determined as
fol lows :
Tcta, wt of 02 - ..289 - 3.453
Total wt of air = 4.289 ' lb ai = 14.921
waste
ir\
I
Excess wt of 02 = 3.453 - 0.805 = 2.648
Excess wt of air = 14.921 - 3-479 = 11.442
Using 328.9 percent excess air, the calculations for the products
of combustion are summarized in Table D~3.
I f a 20 percent CO. reduction in the scrubber is assumed,11 the
composition (percent) of the combustion products is as follows:
C02 = 4.57 - (0.2) (4.57) = 3.66
02 = 16.04
N2 = 79.39
Total 99.09
-------
The corrected concentration (percent) is as follows:
C02 = (3.66 T 99.09) 100.0 = 3-7
02 = (16.04 * 99.09) 100.0 = 16.2
N2 = (79.39 * 99-09) 100.0 = 80.1
TABLE D-3
DETERMINATION OF COMBUSTION PRODUCTS FOR TEST NO. 2
m
mH
mro
SO
\
V
2.
Combustion product
= (0.2837) 3.66
2
Q = (0.0396) (8. 94) + 0.21 + (0.0263) (14.921)
= (0.0006) 2
2
= excess
= (0.7685)04.921) + 0.0048
Total
m M V %M
1.038 44 9-133 4.57
-;,- * * *
0.001 64 0.000 0.00
2.648 32 32.024 16.04
11.472 28 158.554 79-39
199-711 100.00
-Not applicable.
72
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