PROCEEDINGS FROM A
TECHNICAL CONFERENCE ON
WASTE-TO-ENERGY TECHNOLOGY UPDATE - 1980
(April 15 and 16, 1980)
by
G. Ray Smithson, Jr.
BATTELLE
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
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EPA Report Number
September, 1980
Proceedings from a
TECHNICAL CONFERENCE ON
WASTE-TO-ENERGY TECHNOLOGY UPDATE - 1980
(April 15 and 16, 1980)
by
G. Ray Smithson, Jr.
BATTELLE
Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
Grant No. R806653010
Harry Freeman
Incineration Research Branch
Industrial Pollution Control Division
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory-Cincinnati, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or recom-
mendation for use.
ii
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FOREWORD
This report contains the proceedings of a technical conference held
in April of 1980 to review the status of U.S. EPA's waste-to-energy research
programs. The information contained herein will be of interest to those in
the private and public sectors working to develop and utilize waste-to-energy
technology.
Requests for information on the topics discussed in the report should
be directed to the Incineration Research Branch, IERL-Ci or to the individual
authors.
David G. Stephan, Director
Industrial Environmental Research Laboratory
Cincinnati, Ohio
iii
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CONTENTS
Page
FORWORD iii
INTRODUCTION 1
CONFERENCE PROCEEDINGS 4
Session I - Conversion Processes
Pilot Scale Pyrolytic Conversion of Mixed Wastes to Fuel .... 4
Chemical Reclamation of Scrap Tires ..... 14
The California Mobile Pyrolysis System 32
Thermochemical Conversion of Biomass to Gasoline 42
Energing Technology for Maximum Conversion
of Waste Cellulose to Ethanol Fuel 50
Atmospheric Fluidized Bed Combustion of
Municipal Solid Waste: Test Program Results 52
Session 2 - Combustion
Evaluation of the Ames Solid Waste Recovery System 80
Test Firing Refuse Derived Fuel in an Industrial Boiler .... 88
Co-Firing Refuse Derived Fuel (Dross) in
A Stokered Boiler 100
Corrosion Inhibition in Refuse-to-Energy Systems 106
Co-Firing Densified Refuse-Derived Fuel
in A Spreader Stoker-Fired Boiler 112
Co-Firing Fluff RDF and Coal in A Cement Kiln 118
Steam Pyrolysis of Organic Wastes As A Source
of Chemicals and Industrial Feedstocks 138
Session 3 - Environmental Assessments and
Pollution Control Technology
Environmental Assessment of Waste-to-Energy
Conversion Systems 148
Emissions Assessment for Refuse-Derived Fuel Combustion .... 156
Combustion and Emission Assessment of Refuse-Derived
Fuel Cofired with Pulverized Coal 166
Pilot Scale Evaluation of Four Refuse-Derived Fuels 176
Application of Slipstreamed Air Pollution Control
Devices on Waste-as-Fuel Processes 194
Treatment of Wastewaters from Refuse-to-Energy Systems 200
iv
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PROCEEDINGS FROM A
TECHNICAL CONFERENCE ON
WASTE-TO-ENERGY TECHNOLOGY UPDATE - 1980
(April 15 and 16, 1980
to
U.S. ENVIRONMENTAL PROTECTION AGENCY
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
CINCINNATI, OHIO
from
BATTELLE
Columbus Laboratories
July 30, 1980
INTRODUCTION
The U.S. EPA is vitally interested in the dissemination of the
results of its research and development activities to inform potential users
and to encourage widespread utilization of the technology under development.
The Agency also is interested in the assessment of its research and in
acquiring extramural input to the planning of future research and development.
One of the more effective means to accomplish these goals is to sponsor
periodic technical conferences whose basic objective is to provide an update
of the status of technological developments in areas of interest. One such
area is the utilization of the energy contained in municipal and industrial
wastes for useful purposes.
The concept of recovering energy from wastes is not new but this
practice has not been adopted to any significant extent within the United
States. However, for several years there has been growing impetus in the
U.S.—both within the private sector and Federal, state, and local govern-
ments— to develop various techniques for recovering energy from the combustible
-------
fractions of solid wastes and for separating recyclable materials from wastes
generated by industries and large communities. Research efforts have been
expended on many technological approaches and several have been developed to
various stages of practice.
Acting upon the belief that a technical conference on the status
of waste-to-energy research activities would be beneficial and timely,
Battelle Columbus Laboratories proposed such a conference to U.S. EPA. The
purposes of the technical conference were:
• To review the status of relevant research and
development activities being supported by U.S.
EPA's Industrial Environmental Research Labor-
atory (IERL-Ci) at Cincinnati, Ohio.
• To consider the most effective means for the
commercial exploitation of the results of this
research.
• To review areas for future research and to
recommend strategies for the implementation of
such research.
After Battelle's grant proposal was accepted by the U.S. EPA,
the specific objectives and mechanisms for conducting the technical conference
were developed jointly with a steering committee composed of representatives
of these two organizations. Following the adoption of the specific objec-
tives and mechanisms, this committee selected speakers and discussions leaders
from various organizations conducting R&D in waste-to-energy systems for
IERL-Ci. These individuals were invited to participate in the conference with
the understanding that the findings and recommendations would be made available
to persons and organizations interested in this area of technology. The final
agenda for the conference was as follows:
2
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Tuesday, April 15, 1980
Session 1 - Conversion Processes
Registration and Coffee - Foyer
Introduction
Welcome
Session Overview - Walter Liberick, U.S. EPA, IERL
Pyrolysis of Mixed Waste to Fuel - Herbert Kosstrin, Energy Resources Co., Inc.
Pyrolysis of Industrial Waste - George Frazier, University of Tennessee
Portable Unit for Pyrolysis of Agricultural & Forestry Wastes -
Herbert Kosstrin, Energy Resources Co., Inc.
Coffee Break
Bench Scale Pyrolysis to Polymer Gasoline - Jim Biebold, Solar Energy
Research Institute
Bio-Conversion-Acid Hydrolysis - Charles Rogers, U.S. EPA, MERL
Fluidized Bed Combustion of Solid Waste - Lyn Preuit, Combustion Power Co.
Luncheon
Guest Speaker - Dr. Eugene Moulin, University of Dayton
"Stress is Contagious"
Session 2 - Combustion
Session Overview - Bob Olexsey, U.S. EPA, IERL
Evaluation of Ames Energy Recovery System - A1 Joensen, Iowa State University
Firing of Solid Waste in an Industrial Boiler - Gary Boley, City of
Madison, Wisconsin
Cofiring Refuse Derived Fuel (RDF) Dross in a Stoker Boiler -
Fred R. Rehm, Department of Public Works, Milwaukee, Wisconsin
Effects of Using Solid Waste as a Supplementary Fuel - H. H. Krause,
Battelle Columbus Division
Coffee Break
Cofiring Densified Refuse Derived Fuel in A Spreader Stoker Fired Boiler -
Ned Kleinhenz, Systems Technology Corp.
Cofiring of Solid Waste in a Cement Kiln - Cliff Willey, State of Maryland
Pyrolysis of Agricultural Wastes in a Steam Atmosphere - Michael Antel,
Princeton University
Wednesday, April 16, 1980
Session 3 - Environmental Assessments and Pollution Control Technology
Session Overview - Harry Freeman, U.S. EPA, IERL
Environmental Assessment of Waste-to-Energy Processes - K. P. Ananth,
Midwest Research Institute
Emission Assessment from RDF/Hazardous Waste Combustion - Fluidized Bed -
Jim Chrostowski, Energy Resources Co., Inc.
Emission Assessment from RDF/Hazardous Waste Combustion - Stoker Fired -
John Allen, Battelle Columbus Division
Coffee Break
Emission Assessment from RDF/Hazardous Waste Combustion - Suspension Firing -
Robert Pease, KVB, Inc.
3
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Cofiring of four RDF's in a Pilot Scale Facility - Richard Brown, Acurex, Inc.
Air Pollution Control for Waste as Fuel Processes - Fred Hall, PEDCo
Environmental, Inc.
Water Pollution Control for Waste as Fuel Processes - Gordon Treweek,
James M. Montgomery, Inc.
Luncheon
The conference was held in Cincinnati, Ohio. The proceedings of the
conference are included in this report.
3a
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PILOT SCALE PYROLYTIC CONVERSION
OF MIXlED WASTES TO FUEL
by H.M. Kosstrin, Ph.D.
Introduct ion
One of the more promising techniques for reclaiming
energy from municipal solid waste is through pyrolysis,
which is the destructive distillation of waste materials
thereby converting them to clean fuels such as low-Btu gas,
residual oil, and char.
EPA has been involved in the development and demonstra-
tion of several different pyrolysis technologies such as the
Landguard system based upon a rotary kiln, the Tech-air
concept based upon a fixed bed pyrolyzer, and "Flash Pyrolysis"
based upon an entrained bed heated with recirculating hot
char. While all of these technologies are based upon
pyrolysis, all of them produce different energy by-products
because of the different reactor characteristics and oper-
ating parameters inherent in each one.
The objectives of the work being carried out by Energy
Resources Co. are to explore the kinetics of pyrolysis of
municipal waste and agricultural wastes and to develop a
data base on pyrolysis that will allow design engineers to
select pyrolysis system operating conditions for commercially
available systems that will provide the desired mix of
product yields given the mixture of wastes available in a
given geographical area. Because the results of the data-
taking efforts will be extrapolated to full-scale systems,
it is necessary for the experimental work to be carried out
on a pilot plant scale.
The work performed included a literature survey of
pyrolysis to determine the properties of various wastes and
the reactor operating variables which would have a signifi-
cant influence on the project. With these data in hand, a
fluidized-bed pilot plant was constructed to carry out the
collection of kinetic data. The data analysis included
product characterization of the char, oil and gas along with
the development of a prediction model for the oil. The
various parameters that were varied are listed in Table 1.
The result of the data base compiled is to assist the
design engineer to understand the important trends in
pyrolyzed design.
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TABLE 1
PARAMETERS VARIED
Reactor Temperature
Fluidization Velocity
Feed Rate of Waste
Bed Height
Feed Particle Size
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Pyrolyzation of Wastes
The data obtained concern the conversion of a wide
range of wastes to fuels in a fluidized-bed pyrolysis
system. The materials pyrolyzed in both Phase I and Phase
II of the test program are shown in Table 2. The variables
studied as to their effect on the final products of pyrolysis
were temperature, fluidization velocity, feed rate of
pyrolyzable material, bed height (static), and particle
size.
Various experimental conditions other than pyrolysis
were run as a means of determining the usefulness of the
system. These included steam gasification (pyrolysis),
partial oxidation, combustion, and steam partial oxidation
runs.
The major conclusion that comes out of this work is
the importance of secondary reactions in determining the
final product mix of the various waste materials. Pyrolysis
occurs in two steps as described in the modeling section of
this report.
1. Primary decomposition--devolatilizes the feed into
its light fractions, oil and gas, and leaves a
residue generally considered a char. The quality
of the char depends upon the temperature of pyrolysis
of the char formation. The char contains the
inerts from the feed, generally considered ash.
2. Secondary decomposition—these secondary reactions,
which predominate above a critical temperature,
devolatilize the oil produced via the primary
reactions into a gas and a residue. This residue
is additional char.
From work performed during Phase I of the project, an
analytical expression for the yield of pyrolytic oil and
gas, taking into consideration both primary and secondary
reactions, is derived in the modeling section of this
report. The data obtained confirm the analytical expression.
Figure 1, the yield of pyrolytic oil for sawdust, shows
the general shape of the oil yield curve. The secondary
reactions begin to dominate after 400" C. At temperatures
above 400* C the yield of pyrolytic oil decreases and the
corresponding yield of gas increases because of these secondary
reactions. The development of an analytical expression for
the formation of gas from both primary and secondary
reactions has been accomplished. The analytical expressions
are shown in Tables 3 and 4.
6
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MATERIAL: SAWDUST (SAW)
1.5
uj
a.
u»
O
|
a
-j
UJ
>
-J.
o
».3
1-2
1.1
o cP
o
THWPSPATUflS IOSGSSBS Ci
Figure 1. Model curve for pyrolysis oil yieid data of sawdusx.
7
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TABLE 2
MATERIALS PYROLYZED
INDIVIDUAL
Phase I
Phase II
Paper
Sawdust
Corncobs
Waste Oil
Municipal Solid Waste
Sludge
Tires
Plastics
Wood Chips
Pyrolytic Oil
Wheat Straw
Rice Straw
Cotton Gin Waste
Pine Bark
Industrial
Char (from
Sewage Sludge
pyrolysis of
sawdust)
Coal
MIXTURES
Paper + Sawdust
Corncobs + Manure
Paper + Plastics
Coal + Sawdust
Coal + Sludge + Munic-
ipal Solid Waste
Coal + Municipal Solid
Waste
8
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TABLE 3
ANALYTICAL EXPRESSION ?OR THEORETICAL GAS YIELD
vqas = 1-C-^Sil t1 " oil (I"3)! 'gas
vSil oil * * ' °
wnere
C = measured char yield, as provided by the data, mass
fraction of refuse fed.
= ultimate oil yield, from oil yield correlation,
mass fraction of refuse fed.
1 - e-K't'
3 1 -
k 111
Jc' = ko e-E'/ST
t' = a
/ vA
•oU = ! - 1 * 'S x e"koUl=s-tf)
*oil S
koil 3 (*o)oil e"soil/RT
Ts = sampling time, provided from data
ts-t^ = lag time between start of feeding and
start of sampling, provided from data
a = mass fraction of cracked oil which forms
gas, must be 0 < a <_ 1
~ = 1 - 1 V"Ws x
3 *gas s
*gas 3 (*0)gas e ~'<3as/^T
The terms 4, , and Tl were obtained directly from the oil
yield model, as was except that the subscript "oil"
was not used before. The other terms, a, *aas' an<^
!
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TABLE 4
ANALYTICAL EXPRESSION FOR THEORETICAL OIL YIELD
t —V ' a /t/1 e — k ( t e™ t f )
V .. = V .. 1 - e * a/vA 1- 1 - e e
oil oil
k1a/vA kr s
Where
voil = Mass of oil leaving the bed during the sampling
period, per unit mass of the refuse fed (lb/lb).
V*0q = Value of voil for an infinitely long residence
time of the solids in the bed with no secondary
react ions.
t' = a/vA, sec
1 - e~k,t'
* ' = 1 -
k't
1 -
1 - e
-k
TS
kr :
-k(t -t )
e sr
k0 e
-E/kT
k'
K0
-E'/kT
The data from the individual pyrolysis experiments give us
the parameters ts, t', ts-tf and T. R is the
universal gas constant defined as R = 1.987 cal/'k-mole,
with the temperature (T) in degrees Kelvin. Vqq must
be between 0 and 1.
The remaining parameters must be fitted to the data.
These are k0' , kg, E1, E, V*i;L. A complete computer fit
of these five parameters was accomplished.
10
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The ability to predict the yield of pyrolysis products
by analytic expressions is important when trying to optimize
a particular pyrolytic product, as is the case Cor several
pyrolysis systems now in operation.
The produces of pyrolysis are pyrolytic oil, char, a
low-Btu gas, and water. Depending on the feed material the
char product will contain various amounts of ash. Of the
five variables studied, temperature had the greatest effect
on the various product yields. Along with variation in the
yields of the various products with temperature, the quality
(heating value) of the different energy products changes,
as is discussed in the section on product characterization.
The remaining four variables generally produced a
perturbation about the change caused by the temperature
variation.- Bed height over the range studied had a
negligible effect on the data. The remaining variables,
feed rate, fluidization velocity, and particle size, had the
effect of perturbing the general results caused by the
temperature variation, but in the ranges studied these
variables did not show an appreciable effect on the output.
(Figure 2 shows the variation of the gas yield due to
several parameters.)
Phase II testing allowed further investigation of the
effects of particle size, fluidization velocity, and feed
rate on the pyrolysis process, by providing a greater
variation in magnitude of each of these variables. Results
indicate the same minimal perturbations about the general
temperature trends for variable feed rates. High and low
fluidizacion velocities also seem to show a minimal effect,
except in some cases where gas composition seems to be
affected. Phase I tests on tires suggested that particle
size could have a more profound effect than simply per-urbing
results about the general temperature trends. Phase II test
results on pine bark of two particle sizes also indicate a
more definite effect due to this variable.
Conclusion
The modeling of the yields of pyrolytic oil from the
various data runs shows a high degree of similarity between
the several materials that were pvrolyzed in the fluidized-
bed reactor. With some detailed work the ERCO model for the
prediction of pyrolytic oil and gas yields from the fluidized-
bed pyrolysis of waste products could be expanded to predict
the behavior of both fixed-bed pyrolysis systems, and
entrained-flow pyrolysis units.
11
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OPERATING NODEtPVROLVSIS
HATER I ALi5 AUDlJST
0.8-,-
0.6-
0.4
o.s -
o.0
KEY:
X
"T—i—I—r
f ltd
fluidiiiliun
Bad
Symbol
Atu
Vtioclly
H*ighl (m|
o
Lo
Lo
0.6
X
lii
LO
oa
Q
Hi
III
0.6
A
Lo
HI
06
O
to
Lo
0.3
~
Hi
Hi
0J
t
Lo
Hi
0J
4
Hi
Lo
OJ
R
Rtplium
• o
"i—i—i—r~
» .•
•I 1 1 1~
O .
-t—i—i—1~
300 400 500 600 700
TEMPERATURE (DEGREES C.)
GAS YIELD (UT. FRXN . OF FEED)
eee
900
Figure 2.
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Chemical Reclamation of Scrap Tires
George C. Frazier, S.-M. Chan, 0. L. Culberson, J. J. Perona and J. W. Larsen
Departments of Chemistry and Chemical Engineering
The University of Tennessee
Knoxville, TN 37916
paper presented at the conference
"Waste-to-Energy Technology-Update 1980"
Sponsored by
U.S. Environmental Protection Agency
Netherland Hilton Hotel
Cincinnati, Ohio
April 15-16, 1980
14
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Chemical Reclamation of Scrap Tires
George C. Frailer, S.-M. Chan, 0. L. Culberson, J. J. Perona, and J. W. Larsen
Departments of Chemistry and Chemical Engineering
The University of Tennessee
Knoxville, TH 37916
Introduction
Interest in the utilization of scrap cires as a source of chemicals, fuel,
and carbon black has bean increasing in recent years, due. noc only to environ-
mental regulations buc also co the fact chat chemicals and fuels based on
pertroleum and natural gas have been rising in price at rates much greater
than the general inflationary trend. Numerous attempts are therefore being
made around the industralized world to recover chemical ana fuel values from
tires (See 3erry, 1979, for a sucnnary of these developments). Most of the
current processes being developed for this purpose rely on pyrolysis of the
rubber, by one method or another, requiring the heating of the rubber co
temperatures in the range of 500-600°C, or above.
Our vork, sponsored by the U.S. Environmental Protection Agency and
supported in part by the Tennessee Valley Authority, utilizes a cacalycic-
pyrolytic process operating in the temperature range of abouc 3o0-A00°C, co
convert the scrap rubber to hydrocarbon gases, oil, and carbon black. The
catalytic agent ve have used the most is molten zinc chloride, although other
halo salts are also effective (Larsen and Chang, 1976). The results ve present
in this paper are based exclusively on zinc chloride. Molten sales have been
used previously to break down large organic molecules. For example, Zielke et
( 1966 ) developed a process vhich become known as the Consol Synthetic
Fuel (CSF) process for direct liquefaction of coal, using molten zinc chloride
a catalyst and heat transfer medium.
I" is normal practice in the chemical process industries co develop a
"conceptual process design" in the early scages of an actual project, in
15
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order to identify crucial areas requiring further development, to evaluate
various process options which may be available, to assess the overall
technical feasibility of the project, and lastly but most importantly, to
establish at the outset whether or not the process has the potential for
economic profit. In this context, the objective of the work we report on
here has been to obtain that bench scale experimental data required for the
formulation and evaluation of a conceptual process design for the conversion
of scrap tires to chemical and fuel products by molten salt pyrolysis, and
to use this design as a basis for estimating the potential profitability of
the process. Our experimental results and associated economic analysis in-
dicate that such a processing plant converting 22,500 t/yr of tires has the
potential for profit at current chemical prices, energy prices of $3-$4/MM
Btu, assuming the carbon black, the major product, is marketable at prices
in the range of at least L2c/lb. Although there are a number of process steps
requiring demonstration at the pilot plant scale, the biggest unknown at this
point in our process is the marketability of the carbon black. A pilot
plant is required to generate sufficient quantities of this material for test-
ing its suitability in products such as rubber, ink, and plastics.
Although molten salt technology is not easy, advantages of this process
lie in its relatively low operating temperature, in the range of 360-400°C,
and the fact that there is no need to pulverize the tires. However, we do
chop the tires for compaction purposes, in order to increase the reactor
throughput. Further, the relatively large pieces of fiber glass and wire
remaining after the chopping operation appear to be readily separated from
the carbon residue downstream of the reactor. A test of this separability
at the pilot plant scale is desirable.
Bench Scale Results.
A large scale reactor utilizing this technology will likely be a batch
type, which is alternately charged with rubber, flooded with salt, and sub-
16
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sequently discharged, w'e therefore simulated this procedure is our bench scale
work in order chac our processing conditions and produce yields would corre-
spond co wnac mighc be achievable in a large scale plane. Bench scale work
is necessarily small scale so we ware unable co work with large pieces of a
cira. Our reactor was 2 inches i d and 12 inches long, and cur nose con-
sistent, reasonably reproducible results were obcained when we charged che
reactor with scrips cut from a cire which were about 5/15 inch x 5/16 inch x
10 inches-, for a cocal charge weight in che range of 160 grams. A layouc of
our bench scale apparatus, constructed of 316 stainless steel, is shown in
Figure 1. The encire apparatus was heated electrically and insulated with
a calcium silicate to mimimize heat loss. The salt flowed by gravity from
che reservoir, through che reactor, co the receiver. Contact tines of che
salt with the rubber ranged from 2 to 3 minutes to 30 to 40 minutes. However,
the reaction was generally essentially over in less than 10-12 minutes, de-
pending on canper3ture. experimental runs were made -with reaction temperatures
in che range of 330 to 400"C. The carbon black residua was readily separated
from the fiberglass tire cord after a run, due to its high f"lability, by
crushing and screening. It is necessary to wash salt from "he carbon black,
but a small amount of chloride remains in both the carbon black and also in
the product oil, che latter presumably in organic form. Small particles of
carbonblack are entrained in che salt, but we have reused the sal: as nany
as four times without apparent loss in its effectiveness in promoting this
pyrolysis reaction.
After a series of exploratory and debugging experimental runs, a sequence
of four runs in che temperature range 360-390°£ gave the average percentage
product yields and analyses shown in Tables 1-3. For each 100 lb of cire feed,
17.9 lb of hydrocarbon gases, chiefly methane, but with substantial amounts
of ethylene, propylene and l-'outene, are produced, 30.7 lb of oil with an
17
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TC Veil
~\
r
JL
Purged Vent
Molten Salt
Reservoir
Flow Meter
Reac'.or
r^\
TC Well
LR
v_y
C Capllliary
D Drain or Discharge Valve
GR Gas Receiver
LR Liquid Product Trap
M 3/4" SS pipe
SR Molten Salt Receiver
TC lnermocouple
Figure 1. flench Scalr Flow Experiment Layout
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~
Producr Yield Annual Yield
We. I of Feed lb x 1CT7
Hydrocarbon Casos 17.9 0.305
Oil 30.7 1.38
C.irbon 3lac5c 44.2 1.99
Rufuse (Steelwira and Fibarglaa) "5.0 0.225
Loss* * 2.2 0.099
local 100.0' 4.5
*
^^For a plant processing 22,500 t/yr of cirea
Esciaaced as 5' of che cocal carbon black.
Table I. riscimacad Products Yields for a Molten Sale Pyrolysis Plane, based
cn che average o£ four Sench Scale Experiaencal Runs.
Component Anneal Yield Mole Percent of
lbs x 10 ^ lb ooles x 10 ^ SC7 i 10 ^ local Gas
Methane 2.52 15.75 5.66 50.1
2thylene 1.50 5.34 1.92 17.0
£:hane 1.63 5.57 2.00 17.7
Propylene 0.730 1.36 0.666 5.9
Propane 0.845 1.92 0.691 6.1
Isobutane 0.384 0.660 0.237 2.1
1-Butene 0.194 0.347 0.125 1.1
Tot*l 7.90 31.4 11.3 100.0
»
Average of Bench Scale Runs 18-21.
Table 2. Caa Analjsis and Yields for a Molten Salt Pyrolysis Plant Proceasln;
22,500 t/yr of Scrap Tires
19
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Component Vol use Z of Annual Yield, gal
Total Oil
Aromaties (BTX) 27.05. 516,000
Olefins 58.85 1,123,000
Paraffins 14.10 269,000
Total 100.0 1,908,000
Density of the oil » 0.87 g/al a 7.25 lb/gal
Table 3. Major component classes in the oil and their yields,
based on Bench Scale Runa 18-21. Annual Yields are
based on a throughput of 22,500 t/yr of tires.
Product Elemental Weight Percent
C H N S 0 CI
Oil 88.20 10.65 0.03 0.51 - 0.39
Carbon Black 87.14 2.28 - 2.10 4.84 0.94
Table A. Elemental Analysis of the Oil and the Carbon Black
from Bench Scale Run No. 18.
20
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analysis of 27.1% aromatics (3TX) are produced, and 44.2 lb of carbon black
are produced. This Latter number cakes into accounc an assumed, combined
refuse (fiber glass cire cord and steel wire) and loss of 7.22. Elemer.cal
analyses of cha carbon black and oil are shown in Table 4. The chloride
concanc of che oil is probably in organic form, but we have noc factored
the economic value of such products into che profitability analysis summarized
here. However, makeup zinc chloride salt requirements vera computed as if che
chloride values in che products were lost.
Salts such as zinc chloride are corrosive, especially if moisture is
present, and our laboratory apparatus of 316 stainless steal experienced cor-
rosion in locations when moisture (from che air) encered che system during
the frequent opening required of an experimental apparacus of this cy?e.
However, ve have provided precautions, such as purges and dry storage for che
feed tires in order to aimimize corrosion problems in those parts of our
conceptual design commercial plant which come into contact with che hoc sale.
Conceptual Design Processing ?lant
Our design basis is a plant which will process 22,500 c/yr of cires, wich
a 90% on-scream factor, and an assumed carbon black recovery factor of 9 52.
This throughput corresponds to 68.5 t/day, which may be on che lower end of
Che size scale for a plant of chta type which can be economically feasible.
A larger plant would be more attractive economically, buc would also be
limited co a fewer number of locations, due to the cost of transporting scrap
cires over larger distances.
The conceptual layout for this plant is shown in Figure 2. Dry storage
is provided for che scrap cires, where chey are chopped inco 12-13 inch pieces
in order co increase cheir bulk density, chus allowing greacer chroushpuc for
a given reactor size. The batch reaccor is charged through a lock hopper
21
-------
lock
llonper
7 I Chopper
2P.5M i/yr '
Vapor
Puroe Gas
Condenser
Compressor
Reactor
Hoi ten
Salt
Reservoir
Product Oi1
Residue
Salt
Oil
Receiver
Produc t
Gas
Receiver
Salt
Res Idue
Hopper
Air
Flue
Dried
ResIdue
Oryer
\ . .Recycle
Filter —{13 - *»¦
Salt Cake
Condensate
Recycle Liquor
Maanet1c
Separator
Screenino
Carbon ti!acV~
Storaqe
Hopper
Ocsinnod for a Scrap lire throughput of ??.SOO t/yr.
Tire Cord
to Baler
Carhon Black Product
. 3s
To S i /r HpiJih i ion
-------
co prevent noise air from entering the system. The zinc chloride sale is
heacad '0/ a direct-fired heater and forced into the reactor by compressed,
dry flue gas, thereby eliminating the need for a salt pump and valves, which
would be troublesome in a system of this type. The reactor loading, reaccion,
and discharging cycle time is estimated to be about 1 1/2 hours and at the
end or the cycle, the gas pressure on the salt reservoir is released, and the
sale drains by gravity from the reactor to the reservoir, until the next cycle.
The reaction temperature is in the range of 430±20°C although we have not
done a sufficient amount of work to deceraine whether or not this is optimum
with respect to product yields and quality. For example, carbon black produced
by "his process at too low a temperature tends to be high in volatiles, whereas
too high a reaction temperature tends to favor a high yield of methane in the
produce gas at the expense of the more valuable olefin gases.
Down stream of the reactor, the product vapor is processed by conven-
tional technology to a gas stream and an oil stream both of which are, pre-
ferabl/, piped "over the fence" to existing refineries rather being stored
and processed on site. Such an arrangement limits ehe location of tire pro-
cessing plants co those locations in which gas (ethylene) and petroleum
refineries already exist, as shown in Figures 3 and 4.
Returning to Figure 2, the 3olid refuse (carbon black, fiber glass, steel
wire) is washed to remove salt.devacered, dried, crushed, and the wire and
fiber glass are separated first by a cagnetic dann and then by a screen to
retain the fiber glas "fluff". Top size of the carbon black at this point
is about 3/3 inch, and requires grinding (not shown) to customers' specifi-
cations. Conventional technology is used throughout this process stream,
although the process needs Co be "piloted" in order to demonstrate the
separability of these solids and co escablish the degree of salt recovery in
the two stage wash tank.
23
-------
Figure 3. Location of Ethylene Plants
in the Continental U. S.
Figure 4, Location of Petroleum Refineries in the Continental U. S.
24
-------
Sale is also recovered from che wash water by conventional technology:
vacuum evaporation, crystallization, filtering, and drying, for racycle Co
che sale reservoir. The saic liquor is diluted ana recycled co che wash
tank, eliminating che need for disposal of salty, "black water". The only
appreciable salt loss from che system is chat carried by che oil and by che
carbonblack, estimated co be about 4.3 x 10^ Ib/yr, for this plane. The over-
all plane material balance is shown on Figure .2.
Economic Analysis and Profinability Escimaces
The major components of che conceptual plant were sized for a
throughput of 22,500 c/yr of tires and their costs (late 1979) were estimated
in accordance vich che data and procedures given by Petsrs and Timerhaus
(1963) and by Guchrie (1969) , using a Marshall and Seevens cose index of
622.7 (fourth quarter, 1979). The Fixed Capital requirements of 4.31 MMS were
then computed according co che summary shown in Table 5. Annual operating
costs were also estimated in accordance with che ratios given by Pacers ana
Tinmerhaus and are sunaarized in labia 6. The cost of the feed tires is lass
certain and depends on numerous factors, an important one of which is hauling
costs (3erry, 1979). We therefore considered this cost a parameter in our
analysis, ranging from 20 co 4Q S/c.
Our initial analysis based on the sale of ail products for fuel indicated
there i3 little possibility (short of a "negative" cira reed cost) a plant of
this type could be profitable with energy prices in che range of 3-4 S/MM 3tu.
As our next case we considered recovery (and marketability at late 1979 prices)
of che major components having value as chemical feed stocks, Cram che product
screams: carbonblack, olefin gases, and the aromatic oils (BTX). The re-
maining gas and oil in che product stream vas assigned fuel values. Prices for
che chemical products were taken from Chemical Marketing Reporter (December 10,
1979), and those products were discounted up co 90S for refining and separation
25
-------
A. Plane Physical Costa
Process Equipment, Delivered (E) $1,092,000.
Installation (.45E) 491,500.
Insulation (.08E) 87,400.
Instrumentation (.18E) 196,600.
Piping (.25E) 273,000.
Electrical (.125E) 136,500.
Buildings (.5E) 546,000.
Site with improvements (.14E) 152,000.
Auxiliaries (.4E) 436,900.
Plane Physical Coat (P) $3,412,000.
8. Indirect Cost3
Engineering and Construction (.15P) 511,800.
Contractor's Fee (0.1P) 341,200.
Contingencies (.15P) 511,800.
Total Indirect Co3t3 (I) $1,365,000.
C. Initial Charge of Zinc Chloride (C) 30,000.
D. Plant Capital Cost (P + I + C) $4,810,000.
Table 5, Fixed Capital Requirements for a Molten Salt Pyrolysi9 Plant
Processing 22,500 t/yr of tires, in late 1979 dollars.
A. Labor and Supervision (Salaries and Wages) $295,000.
B. Plan Overhead (60Z of Sal. and Wages) 177,000.
C. Utilities (17.52 of Total Product Cost) 513,600.
D. Chemicals, Makeup Zinc Chloride 197,800.
(4.71 x 10s lb/yr at 42c/lb)
E". Insurance (1Z of Fixed Capital) 43,100.
P. Taxes (3Z of Fixed Capital) 144,300.
G. Maintenance (5Z of Fixed Capital) 240,500.
H. Operating Supplies (15Z of Maintenance) 36,100.
I. Depreciation
Machinery and Equipment 0 lOZ/yr 380,000.
Buildings 0 3Z/yr 29,300.
J. Interest (8Z of Fixed + Working Capital) 461,800.
Base Operating Coats $2,524,000.
Tabl? 6. Annual Base Operating Coses for 22,500 t/yr MSP Plant.
26
-------
In view of che face that "he grade of our carbon black has vac to be estab-
lished, ve also considered its value to be a paramecer in chis study. The
lower end of che range used was established using che price of che lowest
grade reported in CMS. (Dec. 10, 1979) of 19.2 c/lb and then discounting chis
by .02 c/lb as a reasonable, lower estimate of che value of chis product at
che current time.
Working capital was assumed to be 20% of fixed capical, incerest ac 8" of
total capical, and Sales, Corporate Adminiscracion and Research (SAR) fees
of 10% of revenues 'were charged against che plant. A case analysis sheet is
shown as Table 7, and che profitability (lose in seme cases) is sunmarized
in Figure 5, in terms of Recum on Investment (RCI), as affected by scrap
I
tire and purification costs, and carbon black and fuel prices. Additional dec3'!,
of chis work are provided in our final report (Frazier, et al 1980).
Acknowledgement
This work was supported by Grant Mo. USt?A R80&321. Additional support
was received fron the Tennessee '/alley Auchoricy, Cost information was
supplied by International Baler Corporation, Rawls Division of the Macional
Standard Company and the W. S. Tyler Division of Combustion Engineering.
Carbon Slack Samples were characterized by the Cabot Corporation. .Mr. Robert
Wiesen provided timely assistance in che laboratory. Vithose ^3e contribution
of the above Deoole ana organizations, this project could not have been
completed.
27
-------
TIRES
PURIFICATION
FUELS
CARBON BLACK
40 $/t
30 %
_4 $/MKBTU
15 C/LB
MMS/YR
REVENUES
C2H4,C3H6,C4H8,BTX 1JL2
FUELS I¦24
CARBON BLACK 2.99
REVENUE TOTAL 5.35
LESS 10% SAR 0.54
NET REVENUE 4.81
OPERATING COSTS
BASE (FROM TABLE 6) 2.52 MM$/YR
PURIFICATION .34
TIRE RAW MATERIALS .90
OPERATING COST TOTAL 3.76
GROSS PROFIT 1-05
LESS 46% INCOME TAX 0-43
AFTER-TAX PROFIT 0-57
% RETURN ON $5.77 MM INVESTMENT 9.9
Table 7. Case Analysis Sheet for a Molten Salt Pyrolysis Plant Sized for a
Tire Throughput Rate of 22,500 t/yr.
28
-------
T
"~7
7
1
T
1
30 Purification
GO
90
Cost, %
Carbon Ulack Price, tf/lb
15 18
Fuel Value
$/MM Btu
Scrap Tires Cost, $/ton
Estimated Profitability of a Molten Salt Pvrolysis plant with a Scran Tire through nut of
00 /yi se< la 179 :es Co
-------
References
Berry, Reginald I., Chem. Eng., p.30, Dec 31, 1979.
Frazier, George C., S.-M. Chan, 0. L. Culberson, J. J. Perona, and
J. W. Larsen, "Chemical Reclamation of Scrap Tires", Final Report on EPA
Grant No. USEPA R804321, Spring 1980.
Guthrie, K. M., "Capital Cost Estimating", Chem. Eng. p. 114, March 24, 1969.
Larsen, J. W. and B. Chang, Rubber Chem. and Tech., 49_, 1120 (1976).
Peters, Max S., and K. D. Tiinmerhaus, Plant Design and Economics for
Chemical Engineers, McGraw-Hill Book Co. New York, Second Edition, 1968.
Zielke, C. W., R. T. Struck, J. M. Evans, C. P. Costanzy, and E. Gorin,
Ind. Eng. Chem., Process Des. Dev. 5, 151, 158 (1966).
30
-------
THE CALIFORNIA MOBILE PYROLYSIS SYSTEM
Dr. Herbert M. Kosstrin,
Principal Scientist
Energy Resources Company, Inc.
Cambridge, Mass.
Introduction
A prototype mobile pyrolysis system to convert agricultural wastes
to transportable fuel products is currently under construction. This demon-
stration project is being sponsored by the U.S. EPA and the State of California.
The Solid Waste Management Board of the State of California is directing the
California portion of the operation, and the Fuels Technology Branch of the
Industrial Environmental Research Laboratory, Cincinnati, Ohio, the EPA share.
Energy Resources Company, Inc. of Cambridge, Mass. is the prime
contractor for the project. Major subcontractors are Litwin Engineers of
Houston, Texas, Valley Fabrication Engineers of Fowler, California, and
Alpha National of El Segundo, California.
The mobile pyrolysis unit is a fluidized-bed pyrolysis system for
the conversion of various agricultural wastes into a storable energy product.
The waste products used by this system will be from the Central Valley of
California. The waste conversion system is designed to be built on two
low-boy trailers in order to improve the economics of converting widely
dispersed agricultural wastes to useable fuel products. The pyrolysis system
produces three fuels products, a low Btu gas, a pyrolytic oil, and a char.
The unique features of this system are the mobility of the unit
and the total self-sufficiency from outside fuel sources after start-up.
The system uses the pyrolytic gas generated during waste-to-fuel conversion
process to operate a gas turbine cogeneration system. The cogeneration
system produces the required electricity to operate the system and the heat
necessary to dry the incoming feedstocks. Also, after the fluidized-bed
32
-------
reactor is heated up co temperature with a scar-up fuel, a portion of the
waste is combusced co supply che heac for che fluidized-bed reactor. In
addition, Mo. 2 fuel oil is used as che initial scrubbing or cooling liquor
in che oil separation system. As soon as sufficient pyrolytic oil is pro-
duced, it is utilized as che liquor. In chis manner che mobile pyrolysis
unit is independent of outside fuel sources.
The outputs of chis mobile pyrolysis system are che storable ana
transportable fuel products, pyrolytic oil, and pyrolytic char. These tvo
products have a greater energy density than the wastes from which chey are
generated, and therefore, can be economically transported. In addicion,
these products of pyrolysis are more uniform in composition than their
respective feedstocks and can be utilized by existing fuel systems, whereas
use of the individual wastes would require special boiler design.
Background
The concept of a mobile pyrolysis waste conversion system resulted
from programs sponsored by both the United Scates Environmental Protection
Agency and the State of California Solid waste 'lanagemenc Board. The initial
£?A program, which proved chac stationary pyrolysis of waste products was
an acceptable means of converting waste products co fuels, was carried out
under the auspices of the Fuel Technology 3ranch of IZRL-CIN. In this
program both fixed bed and fluidized bed pyrolysis processes were tasted
and evaluated for several years.
During this time period the State of California Solid waste Manage-
ment 3oard (SVM3) was concerned with disposal of various agricultural waste
products. The waste products which need disposal are cotton gin trash,
rice straw, orchard prunings, manure, and logging and lumber-mill wastes.
These waste products are spread throughout the encire state. In addition,
each of chese waste produces are generated. during different seasons of the
year. The geographic and seasonality dispersion led the SVM3 to conduct a
series of studies evaluating stationary vs. mobile disposal systems.
33
-------
Two major findings convinced che SWMB that a mobile unit was
preferred over a stationary system. One is the high cost of transporting
low density, wet waste products. The second is that a fixed system might
be located in a portion of the state that is not generating wastes year
around and consequently, might not operate for a substantial part of the
year. A State of California report, SB 1395 "Agricultural Economic Feasibility
Analysis", gives the costs of transportation of the various waste products.
The study which resulted in this report found that the cost of transporting
these low-density wet wastes was prohibitively high. And that only a mobile
type system was economically reasonable.
As a result of these independent studies the State of California
and proposed a mobile pyrolysis waste disposal system that converts these
wastes into useable forms of energy.
The System
The major elements of the mobile pyrolysis system can be seen in
the simplified flow sheet (Fig. 1). The major system components are feed
preparation (sizing and drying), thermal decomposition (fluidized bed
reactor), product separation (char and oil), and electrical cogeneration
(gas turbines). The individual subsystems are integrated to as large an
extent as possible in order to maximize the overall efficiency of the system.
The physical system is designed to operate on two low-boy trailers.
Trailer If 1 contains the fluidized bed reactor and product separation systems
and auxiliaries. Trailer it2 incorporates the feed preparation and electrical
cogeneration system. The trailers are forty-eight feet long and forty-seven
feet long, respectively. The tractor and trailer combination weighs less than
eighty thousand pounds each and meets all of the California transportation
regulations for over-the-road operation.
The central element of the mobile pyrolysis unit is the fluiaized-
bed reactor. The reactor converts agricultural and forestry waste products
to useable fuels. The unit uses a refractory sand as the inert fluidizing
medium, and can handle feedstocks with moisture contents as high as 55 percent.
34
-------
The feed preparacion system reduces che moiscure concenc of che
feaascock entering che reactor co much lass than this maximum amount. This
sub-system is composed of a standard hammer-mill-cype shredder and a pneu-
macic-cype cower dryer. The drying systam has been adapted from standard
designs of che cotton ginning industry.
The product separation sub-system collects che storaole and trans-
portable fuel products. The dry mechanical collector (cyclone) captures che
char (density 10-15 lbs/ft"^), and the Venturi oil scrubber collects the
pyrolytic oil (65-75 lbs/ft?). The Venturi oil scrubber is a modification
of a standard wet scrubbing system. The principal change is in the flow
races of the scrubbing medium and che types of pumps employed. The ouinps
are capable of pumping a high viscosity fluid.
The final system coraponenc is che electrical cogeneracion system.
A gas turbine uses che low-Btu gas (150 Btu/scf) generated during che pyroiysis
process co generace che required electricity for the several motors of che
entire unit. The exhaust from the turbine is mixed with cooling air and then
used as che heat source for the drying system. To integrate che system more
completely, che gas turbine package supplies che required fluiaizacion air
for che reactor sub-system.
The Products
The fluidized-bed pyrolysis systam produces thrae fuel products—
a low-3tu gas, a pyrolytic oil, and a pyrolytic char. As can be seen in
Figure 2, "he quantity of che products can be varied by changing che operating
temperature of the reactor. The operating temperature of che mobile pyrolysis
systam was selected in order to maximize che storable fuel products (char and
oil) while producing a low-Btu gas that could be burned in che electrical
generation su'o-systea.
The gas quality chat can be burned in che gas turbine engines can
be as low as 100 3cu/scf. The mobile pyrolysis unic is designed co produce
a gas of 150 Btu/scf qualicy. During scarc-up che turbines will be tested
35
-------
to determine the minimum gas quality that can be tolerated. As the turbines
are shown to be able to burn a low-quality gas, the reactor conditions can
be varied to produce a larger portion of storable oil product.
The char product resembles pulverized coal. The exact physical
nature depends on the waste material from which the char is derived, and
the temperature at which the char is produced. If waste wood is the feed-
stock, and the temperature of the reactor is approximately 1000 F, the char
will have a heating value of approximately 13,000 Btu/lb, an ash value of
less than 10 percent, and a particle size ranging from 1000 microns to 50
microns or less. The volatility of this material is approximately 20 percent.
This char makes an excellent feedstock for charcoal briquets.
The oil product is similar to a heavy residual oil that is highly
oxygenated. Its heating value ranges between 11,000 and 13,000 Btu/lb.
The handling properties of the pyrolytic oil made from wood are different
from a typical residual oil. The viscosity and corrosivity are higher and
the material undergoes chemical changes when stored at elevated temperatures.
However, the sulfur content of this oil is negligible which is of considerable
importance today.
System Efficiency
The principal objective of the mobile pyrolysis system is to dispose
of waste products while producing a transportable fuel product. The energy
flow diagram (Figure 3) shows the split in the energy product for the design
case in which the quality of the low-3tu gas is 150 Btu/scf. This condition
yields a storable energy fraction of 49 percent of the incoming feed. The
additional recoverable energy in this case is used for drying of the feedstock
or it is vented to the atmosphere.
The percentage of storable energy can be increased if the quality
of the gas being burned in the gas turbine can be reduced.
The total system efficiency is increased when operating in a
region where the low-grade heat being rejected by the oil scrubbing system
and excess turbine exhaust heat can be utilized. This situation does occur
36
-------
when ooeracing ac a cotton gin or sawmill. This low-grace heac can be used
co supply che energy for preheat of a steam syscem or a hoc water system.
Schedule
The mobile fluidized-bed pyrolysis syscem is scheduled co be
completed by early May, 1980. The system will chen undergo a chree-monch
shakedown on sawmill waste ac a sice near che fabrication shop. After
complecion of che shakedown phase che unic will proceed on che remainder
or* che 9-month cescing schedule on che remaining waste produces, coccon gin
crash, rice straw, and feedloc wastes.
During this casting period che entire system will undergo complece
analysis as to environmencal amissions, operating characteristics, fuel
product quality, and overall system economics.
37
-------
T1IOSTOCK
0
JfTL
o
sunt doen
onvtn
rttncn
pvnoi y/fh
enAnsrrAnATon
oil cowofNsrn
OIL cooi-Fn
rowrnisson
cownusTon
TiinniNE
CJlNEflAIOn
fucl coMpncsson
TUHOO FAN
¦J IJ LI III
CAS
-------
0 00
Oil YicHd
j
PRODUCT YIELD FLEXIBILITY
AT VARIOUS TEMPERATURES
0 00
n"
y o-
?;o/io
o
I-*
X) 5
V >
lL o0.20
o
il. .«•
0.00
ooo° r i,ioo°p i /i oo° r i.7oo"f
Char Yinkl
Gos Yield
2 <« C10
v ^
"0.20
«¦ o 0.70
o S 0/10
000° I" 1.100°F 1.400°r 1,700"F
boo<>f
1,100° F
1/100"F 1.700"F
-------
FLUID ono
CONVERSION
PROCESS
r
CHAR :| 27%
27%
OIL
f \J
turbine
Mcn&llNEIl '2%
34%
1%
fxmausi
II HAT
PROCESS
CLECrniCITY
STORAOLE
'enf(u;y
i RECOVERABLE
' ENERGY
t100°F
orftHiDfHjnonraSntJ^ElflnDM&OiFDmiJfitrDnnfQimraQDnd -»%
LOSSES
-------
THERMOCHEMICAL CONVERSION OF BIOMASS TO GASOLINE
J. P. Diebold and G. D. Smith
Naval Weapons Center
China Lake, CA 93555
ABSTRACT
This noncatalytic process involves the low pressure,
selective pyrolysis of organic wastes to gases containing
relatively high amounts of ethylene and other olefins.
After char, steam, and tars are removed at low pressure,
the gases are compressed to 450 psia (3100 kPa) for
purification. The concentrated olefins are then further
compressed to 750 psi (5200 kPa) and fed to the poly-
merization reactor where they react with each other to
form larger molecules, 90% of which boil in the
"gasoline" range. Using organic feedstock derived from
trash, gasoline was produced on a bench scale system
which had the same appearance and distillation charac-
teristics as gasoline made from pure ethylene which had
an unleaded motor octane of 90. Preliminary economic
analyses indicate that the process is currently compe-
titive with petroleum derived gasoline. This program has
been funded by the U.S. Environmental Protection
Agency.
INTRODUCTION
The petroleum resources of the free world are becoming
increasingly scarce and expensive. As the search for new
oil goes further out to sea and deeper in the ground, this
new oil will be increasingly expensive to produce. Many
of the existing oil fields in some countries apparently
will not be pumped at their maximum rate in an effort to
save that oil for future generations when the price will
be presumably higher. Thus, it appears advantageous to
develop sources of synthetic petroleum and in particular
synthetic gasoline. Due to the high volumetric energy
content of hydrocarbon liquids, they would have been
invented for mobile transportation if* they had not been
naturally occurring. Usually the term "synthetic
petroleum" brings to mind coal and/or oil shale
liquefaction. However, these processes will involve a
considerable amount of environmentally questionable
strip mining and are normally considered to require a
large amount of scarce water resources. The process to
be discussed in this paper involves the use of organic
wastes and/or biomass in a noncatalytic selective process
to produce unleaded, high octane gasoline. Byproducts
are fuel oil, lubricating oil, ash, water vapor, and carbon
dioxide. Commercial sized plants would resemble small
oil refineries in many aspects and could be widely
deployed in order to be near the feedstock source.
The advantage of producing gasoline rather than other
fuel forms becomes apparent by comparing common fuels
on a relative wholesale value basis. If a wholesale value
of $1.00 per unit of energy is assigned to natural gas for
interruptible commercial usage, then in 1975 the value of
noninterruptible domestic natural gas was $1.42 per unit
of energy. Number six fuel oil was $3.08, while the value
of gasoline was $5.48 per unit of energy. Recent relative
increases in the value of natural gas have reduced the
ratio of gasoline to natural gas prices temporarily.
However, the widely predicted continuation of today's
petroleum shortage will cause the value of gasoline to
escalate at a rate much greater than boiler fuels. This is
because, although coal can again become the primary
boiler fuel for the nation, coal fueled automobiles naving
today's performance are not being actively considered.
The conversion of organic waste to automotive fuel was
consequently investigated for remote military instal-
lations in a Department of Defense Advanced Research
Projects Agency sponsored program because of the high
potential value of the product. The synthesis of
methanol from organic wastes was evaluated in detail
with mass and energy balances developed about two
different flow diagrams. This approach would have
pyrolyzed the organic fraction to form synthesis gases
which would then have been compressed, purified, and
catalytically reacted to form methanol. During the
course of this study (1), several references were found
which indicated the possibility of using pyrolysis to form
a significant amount of low molecular weight
hydrocarbons rather than just carbon oxides, methane,
and hydrogen. These gaseous hydrocarbons of interest
were predominantly ethylene, propylene, and other
olefins.
In the 1930's the oil industry began to extensively
pyrolyze ("crack") crude oil to increase the yield of
gasoline. By-products of that process included large
amounts of ethylene, propylene, and butylene. Extensive
research was performed on the utilization of these by-
product gases which led to the commercialization of
their conversion to gasoline by both catalytic (2) and
non-catalytic (3) processes. The gaseous hydrocarbons
were compressed, purified, and then heated such that
they reacted to link up with themselves to form the
larger gasoline molecules by polymerization. This
process produced a liquid which was over 75 percent
gasoline. The proposed process substitutes solid organic
wastes for the crude oil feedstock, but otherwise
parallels the petroleum process used to make polymer
gasoline. Due to the high ethylene content of the olefins
formed during pyrolysis of cellulosic materials, the
thermal or non-catalytic polymerization was chosen for
42
-------
this process because the traditional catalytic method
polymerized ethylene with difficulty.
The overall process for converting organic wastes to
gasoline consists of: first, the pyrolysis of the wastes to
gases containing large amounts of olefins, i.e. ethylene,
propylene, etc.: second, the compression and purification
of the olefins: and third, the polymerization of the
smaller olefins to form larger gasoline molecules.
Overall this amounts to a process which removes the
oxygen from the cellulosic wastes to produce a gasoline
consisting of hydrocarbons. Most of the rejected oxygen
is in the form of carbon dioxide.
The critical technology that this program needed to
demonstrate was the pyrolvsis of cellulosic organic waste
materials into gases containing large amounts of olefins
and their subsequent processaoility. If the selective
pyrolvsis could oe verified, and demonstrated, then the
remainder of the process to make gasoline was thought
to be relatively straightforward due to industrial
experience with similar processes. In effect, the process
parallels that of an oil refiner/ with the most significant
difference being the use of today's cellulosic waste
material rather than eons-old organic matter (crude oil)
as a feedstock.
The potential impact this process could have on the
gasoline consumed in the United States appears to be
substantial. Assuming that this process will undergo a
traditional developmental or scale-uo period followed by
a well financed program with high national priority,
widespread deployment of conversion plants could be
accomplished by 1998. A recent Market Oriented
Program Planning Study by the Department of Energy
(DOE) estimated the U.S. gasoline consumption in 1990
at 115 billion gallons (4). If 10% of the land currently in
forest, pasture, or range usage having at least 25 inches
ot" precipitation and less than 30?6 slopes were to be
developed for silvicultural energy farms, approximately
2S°6 ot the gasoline consumed could be produced from
the resultant biomass (5). Another 13% of the projected
gasoline consumption could be produced from crop
residues and spoiled forages (6); If the trash generated
by 120 million people were to be converted to gasoline,
4% of the 1990 gasoline consumption would result. From
these three biomass sources, slightly less than half of the
projected 1990 gasoline consumption could be produced
by the conversion process described without impacting
food production to any extent. To determine the net
energy produced by the overall system including energy
inputs to grow, harvest, transport, and process biomass
into gasoline requires a very specific analysis for a given
site and is outside the scope of this paper. However, the
process would have the best economics where the
biomass is a waste by-product and wriich now requires
energy for its disposal.
Initial preliminary economic analyses looked very
promising for fairly small cities to rid themselves of
trash so the Environmental Protection Agency (IERL,
Cinn.) was contacted to generate interest in this
economical approach to trash disposal. As a result of
their interest in this process, an interagency agreement
(EPA-IAG-D5-0731) was written for NWC to pursue the
technical and economic feasibility of converting organic
wastes to gasoline by evaluation in a bench-scale unit (5
kg/hr). This EPA effort was begun in June 1975 and has
been continuing.
EXPERIMENTAL
Pvrolvsis
Figure 1 shows the currently evolved pyrolysis schema-
tic. A finely ground organic fraction of municipal solid
waste is continuously fed by a one-inch screw feeder. At
the end ot the screw feeder, the feed is fluidized and
conveyed by a carrier gas stream (normally carbon
dioxide) to the steam ejector. The mixture of solid
waste, carrier gas, and steam then enter a long, red-hot
3/4 inch diameter tubular reactor. Reactor lengths of 2
and 5 meters resulted in pyrolysis times of aoout 50 to
ISO milliseconds, respectively. The char is removed
from the pyrolysis stream in a three inch diameter
cyclone. The steam and tars are condensed out of the
pyrolysis gas stream bv the water quench system. The
noncondensible gas stream volume is measured by an
orifice flow meter and then either flared off or fed into
a three stage compressor for storage at high pressure.
This system pyrolyzes a nominal 5 !
-------
The composition of the pvrolysis products has been found
to be a function of the combination of temperature,
residence time, and especially the dilution of the solid
wastes by inert gases inside the reactor. As shown in
Figure 2, the total hydrocarbon product (other than
meth8ne) can be varied by as much as 165% depending
upon the relative dilution of the pvrolysis gases. Using
the more favorable combination of these variables, a
pvrolysis product distribution such as that represented in
Figure 3 can be attained using organic material obtained
from municipal solid wastes. Slightly more than half of
the energy contained in the organic waste can be
recovered in the gasoline precursors. About one third of
the energy is recovered in the "medium Btu" by-product
gas stream of carbon monoxide, methane, and hydrogen.
About one-seventh of the energy is recovered in the
char, which has a heating value similar to lignite coal.
7M°C PVROLYSIS TEMPERATURE
75a
110
700
7«0
S.1M PrflOUSIS coil
ECO II IT —511 FEED
(1% MOSITURE)
-
2
t U 10 <20 1(0 IOC
I DRY ECO H/M3 GASES
Fig. 2. Pvrolysis Products as a Function of Dilution
•It ITU
SCF IT-ntOOUCT GMES
H, UN
GASOIINI KUCUKSOHS
ism
Fig. 3. Pvrolysis Product Energy Distribution
Pvrolvsis Discussion
Pyrolvsis of cellulosic materials has long been recognized
as the result of several competing reactions taking place
simultaneously. At low temperatures of 200 to 300 C,
the predominant reaction is of dehydration to form char
and water vapor. At intermediate temperatures of 300
to 600 C the predominant reaction is a depolv-
merization or chain cleavage reaction to form
ievoglucosan tars. At elevated temperatures,
gasification is the predominant reaction to form
combustible volatiles. (7) This gasification reaction
itself appears to have at least two major competing
reactions: a) to form olefins, carbon monoxide,
hydrogen, and methane; and b) to form thermally stable,
water soluble, oxygenated compounds. The data suggest
that the olefin forming reaction is favored when the
partial pressure of the pvrolysis products is reduced by
the addition of a relatively inert carrier gas, e.g. carbon
dioxide, steam, methane, nitrogen, or carbon monoxide,
or mixtures of these gases with hydrogen. It is
interesting to note that although the quantity of gases
produced can be varied by the relative dilution, the
relative molar ratios of the gaseous species after water
washing are relatively constant.
The by-product gases could be used to fuel stationary
internal combustion engines to generate shaft power for
the compressors and shredders, as well as to fuel the
pvrolysis furnace along with the by-product char. As was
mentioned, it was. found that the use of steam to dilute
the pyrolvsis gases results in a higher conversion to
gasoline precursors. It now appears that the process will
be optimized by making as much steam as possible by
energy recovery from hot gas streams as well as by
utilizing all of the char and the by-product fuel gases for
process energy. This will result in only gasoline, fuel
oils, and lubricating oils as the products from the organic
fraction. These products will be readily marketable
compared to char, pyrolytic oils, or "medium Btu" gas.
The generation of high pressure, superheated steam to
cogenerate shaft energy and low pressure process steam
may optimize the process.
It is interesting to note that the pyrolvsis conditions
found to be optimum for municipal solid wastes are
coincidentally similar to those used by the petrochemical
industry to pyrolvze naphtha or crude oil to form
ethylene: e.g. about 750 C (M40Q F), steam dilution,
pvrolysis times of less than a second, and iong tubular
reactors having inside diameters of less than five cm (8,
9, 10). It is even more interesting to note that if the
carbon monoxide and carbon dioxide in the pyrolvsis gas
are ignored, and the remaining products are then
normalized, that the relative weight percentages of the
pyrolysis products from naphtha (8), solid wastes, and oil
shale (11) are very similar, as shown in Figure 4. it
appears that the molecular fragments from the pyrolysis
of both cellulosic ana large hydrocarbon molecules are
very similar and that they achieve a similar short-lived
"equilibrium" between the products. If not rapidly
quenched, this psuedo "equilibrium" changes bv the low-
pressure, high temperature polymerization of ethylene,
propylene, and butvlene to form about half benzene and
half aromatic tars with the evolution of hydrogen (12). [f
the pvrolysis system has a very long residence time, the
benzene and tars further react to form char and
hydrogen — the last mentioned being the traditional
products from charcoal kilns, along with carbon
monoxide.
-------
'MSW (ECO ID
err. /OIL SHALE
NAPHTHA v j; kr
(WEIGHT PERCENTAGES CALCULATED AFTEfl CO ANO C02 DELETED)
Fig. 4. Pyrolysis Product Comparison
Polymerization with Pure Ethylene
To avoid the tar formation during polymerization, lower
temperatures can be employed so that the gasoline
fraction in the product is optimized. However, in order
to maintain reasonaole reaction rates, the pr^sure nust
be increased. Temperatures of 400 to 500 C (730 to
950 r) and pressures of 4800 to 5900 kPa (TOO to 1000
psi) were often employed commercially (13, 14). To gain
insights into the exothermic polymerization reaction, an
experimental reactor was constructed as shown in Figure
5. This polymerization effort was conducted
concurrently with the pyrolysis development, so no
purified pyrolysis gases at elevated pressures were
availaole for use. Since ethylene was the largest single
constituent in the gasoline precursors found in the
pyrolysis gases, bottled ethylene was purcnased and Laed
for this study. The ethylene was regulated into a one-
half inch ciameter stainless steel tuoe wnicn had ;een
coiled and placed in a constant temperature, fluidized
sand oath. The sand bath served to initially 'leat the
coiled reactor until the exothermic reaction was
initiated, after which the bath served to remove Lie heat
generated. The ethylene slowly moved down the length
of the reactor for a few minutes while polymerizing.
The polymerized gases were then cooled to condense out
the gasoline and oils. SoncondensaOle gases were
measured and then flared off. Conversions per pass were
as high as 30 percent. The liquids formed had very low
viscosities and when distilled produced aoout 90 oercent
it
REMOTELY OPERATED
VALVE
T
V
oTo
9^
POLYMERIZER COIL
! «N-
I I 1
AIR
CONDENSER
PRESSURE
REGULATOR
TO
FLARE
ROTAMETER
VENT
U L
ETHYLENE
HIGH TEMPERATURE
FLUIDIZED SAND BATH
GASOLINE
RECEIVER
™ig. 3. Experimental Polymerization Reactor
-------
gasoline. This distilled gasoline fraction was tested
following the ASTM motor method and found to have a
90 octane rating in the unleaded condition (the research
method would have resulted in a slightly higher octane
number). The higher boiling liquids will yield a fuel oil
and a lubricating oil fraction.
Based on the pyrolvsis and ethylene polymerization
experimentation it is estimated that 0.28 liter of gaso-
line and 0.03 liter of oils will be produced per kilogram
of 90% by weight organic material (68 gal/ton gasoline, 8
gal/ton oils). The amount of lubricating oil in the oils is
currently conjectured to be fairly small, but with a high
potential total value due to its reported excellent
viscosity characteristics (15).
Bench Scale Purification and Polymerization
The bench scale pyrolvsis gas purification and poly-
merization flow diagram is shown in Figure 6. The
pyrolysis gases are first compressed to 3100 kPa (~450
psi). The purification starts with the removal of carbon
dioxide, hydrogen sulfide, and other water solubles with a
hot, aqueous solution of potassium carbonate (L6). Next
the desirable olefins are absorbed in an organic solvent
with the by-product fuel gases passing through
unabsorbed. The olefin rich solvent is then heated to
drive off the relatively volatile olefins (17). The purified
olefins are then further compressed to 5200 kPa (~-750
psi)Qand fed ^nto the polymerizing reactor held at about
450 C b350 F). The polymerizing reactor consists of a
3 meters long by 1.3 cm diameter 316 stainless steel tube
(10 ft by 1/2 in dia) immersed in a boiling sulfur bath.
The boiling sulfur bath has an extremely high heat
transfer capability and serves to maintain a constant
temperature as it removes the heat of polymerization.
The polymerization reaction proceeds under these
conditions of heat and pressure without catalysts to form
a product consisting primarily of gasoline. After
polymerization, the hot gasoline vapors are cooled,
condensed, and stored. Unpolvmerized olefins can be
recycled.
This bench-scale system is in the final stages of
debugging. The hot carbonate system for carbon dioxide
removal is very selective and has resulted in a carbon
dioxide stream having a purity of greater than 99% by
volume with the primary contaminant being acetylene.
The potassium carbonate solution is easily regenerated,
although it does require a considerable amount of energy
to boil the solution at 120 C (250 F). The hydrocarbon
absorption system needs additional tuning, but has
resulted in a byproduct gas stream containing 20%
hydrogen, 5% nitrogen, 1L% methane, 61% carbon
monoxide, and 2 to 3% gasoline precursors (mostly
ethylene and propylene). The hydrocarbon stripper
system also needs some additional tuning, but it has
resulted in an enriched stream containing as high as 48%
gasoline precursors with 4% hydrogen, 1% carbon
dioxide, 1% nitrogen, 16% methane, and 29% carbon
monoxide as the impurities.
The effect of these impurities in the polymerization was
to lower the partial pressure of the reacting olefins to
slow the bimolecular polymerization reaction. A longer
residence time is indicated in the polymerizer reactor
depending upon the relative purity attainable from the
gas purification system. Using pyrolysis gases made
from organics derived from trash, a small quantity of
synthetic crude oil was produced from the partially
purified gases available. This synthetic crude oil was
distilled and 93% of it boiled in the gasoline range. The
distillation curve for the polymer gasoline made from
pure ethylene was virtually identical to that for the
gasoline made from trash derived organics. The physical
appearance of the two synthetic gasolines is an identical
very pale yellow and with a gasoline odor. Although
sufficient gasoline made from pyrolysis gases has not yet
BY-PRODUCT GASES
(CO.
ch^ h2;
LEAN OIL
TO RECYCLE
OLEFINS
2S0°F
440 psiL2i£H
OIL
750
PSI
430
PSI
430
PSI
BOILING
SULFUR
THERM0SYPH0N
POLYMERIZATION
COIL
PYROLYSIS
GASES —
AT 450 PSI
KHC0
PRESSURE
BOOSTER
POLYMER
GASOLINE
STORAGE
1 ATM
CJ
KHS
Fig. 6. Purification and Polymerization Schematic
46
-------
been produced to allow an octane test to be run. it would
appear reasonable to expect it to nave an octane rating
similar to that of tne gasoline made from pure ethylene.
Additional effort needs to be expended in tne bench scale
system particularly in the areas of: low pressure
pvrolysis gas scruooing to more completely remove the
tar mists: the hydrocarbon absorption and stripping
system to verify that the reported high levels of fas
purification can be attained with gases that contain
carbon monoxide; the addition of a soaking chamber to
the polymerizing reactor to increase Che residence time
to increase the conversion per pass; the addition of a
recycle loop around the polymerizer to increase the
overall yield: the full characterization of the synthetic
gasoline and oil product: and the evaluation of feedstocks
other than trash derived organics. A modest program to
pyrolvze pure cellulose and pure lignin powders to be
able to project biomass potential for this process has just
been started with funding from the Solar Energy
Research Institute.
COMMERCIALIZATION POTENTIAL
It was noted previously that the pyrolysis conditions used
in development for organic waste are very similar to
those used to pyrolyze crude oil and naphtha to ethylene.
It follows chat once che solid wastes are fluidized by the
carrier gas stream, that the technology exists in the
petrochemical and petroleum industry to design and build
commercially-sized organic waste pyrolysis units. Since
similar compression, purification, and polymerization of
the gaseous hvdrocaroons have all been commercialized
in the past, it would appear that the process could be
contracted to any one of several petrochemical or
petroleum construction firms with a fairly low technical
risk. For pilot plant demonstration purposes, it may be
economically advantageous to add this gasoline module
to an existing trash processing plant already in operation
or to locate it in an area having several types of agri-
cultural wastes available.
PRELIMINARY ECONOMICS
Municipal Waste Feedstock
To determine the economic feasibility of the process to
convert municipal trash into gasoline requires a long list
of assumptions. For the use of municipal trash as feed-
stock it was assumed to contain 50% dry, ash free
organic material, '.3% inorganics (iron, aluminum, and
glassl. and the balance moisture. A credit of $4.35 per
tonne (54.40 per ton) of trash processed was assumed for
the value of the reclaimed metals and glass. A yield of
0.19 liters of hydrocarbon liquids per kilogram (45
gal/ton) of trash processed was assumed. The relative
economics of the process were taken to be a function of
source of capital, plant size, gasoline (hvdrocaroon)
value, and the dump fee per tonne of trash credited to
the process. The plant size can be converted to the
population served by the process by assuming a daily per
capita trash generation rate of '2.27 kg/dav (2.5
tons. 1000 daily people). The capital and operating cost
figures are based on those generated by an outside
petrochemical consultant under contract to EPA for a
100 ton per day plant during their evaluation of the
process. The consultant's cost estimate in early 1973
was 57.5 M capital costs and 51.LM annual operating cost
(exclusive of debt service). The capital costs .vere
scaled using 0.S5 as the exponential scaling factor,
whereas 0.20 was used as the labor cost factor.
As will oe illustrated, the method of financing the
construction costs has a significant impact on the
apparent economics of the process. Figure 7 snows che
economics for a plant financed at an interest rate of 3%
and a 25 year amortization. This would be fairly typical
of a municipally financed plant which could be operated
either by the municipality or by a contractor. It is seen
that with a 510/tonne dump fee credited to che plant
that a 250 tonne/day plant would produce gasoline worth
SO. 10/liter (S0.38/gallon).
!« MUNICIPAL AMORTIZATION
u.a rtQHNi inoxgamic «8COv(ky cmoit
,casoun( valu£ vurea ii/gali
Z
X
o
5
^ -10
a
-JO -
,0.21 IO.I
rooo
HJUtT S12*. rONNt /OAV
-ig, 7. Trash to Gasoline Economics with Municipal
Financing
Figure 3 has the same assumptions as before, but with
private enterprise involved at a 15^ rate of return. At a
L5% rate of return, the small '250 tonne per cav plant
with a SlO/tonne dump fee must charge about 50.20/liter
(S0.75/gallon) to meet its financial obligations. For
private enterprise, larger plant sizes are clearly
indicated. For example, at a 15°6 rate of return and the
same dump fee. a 500 tonne per day plant size is
estimated to produce gasoline valued at about $0.l3/liter
(50.50/gallon).
ZS. ?Onn£ • 0>y
Fig. 3. Trash to Gasoline Economics with Private
Financing
-------
The 500 tonne per day plant therefore appears to be an
economically interesting size. One of the problems in
evaluating the economics of this system is to project the
value of gasoline over the estimated 25 year life of the
plant. Figure 9 shows the rate of return on the
investment for a 500 tonne per day plant using the same
bases as before. With a S10 per tonne dump fee and a
current $0.685/gallon wholesale gasoline value, a 23%
rate of return would be realized. If the wholesale value
of gasoline were SI.00 per gallon, the projected rate of
return would be 34%.
(M.asrroNNE reclaimed metals and glass)
50
40
10
3
7.00
1.50
1 00
0.80
0.90
LOCAL WHOLfiSALl GASOLINE VALU* VGAL
Fig. 9. Rate of Return for 500 Tonne/day Trash Plant
Biomass Feedstock
The process to convert trash to gasoline is thought to be
applicable also to agricultural and silvicultural materials.
These organics could be a mixture of wastes and/or
material specifically grown for conversion to fuel. The
assumptions were modified somewhat to reflect the lack
of metal and glass recovery equipment and the lack of
these salvage products. The feedstock was assumed to
contain 90% dry, ash-free organic material. The yield of
gasoline per unit weight of organic material was assumed
to be the same as with municipal trash derived organics.
Similar economic trends are observed with the biomass
processing plants as with the trash plants, but the
economical size of the biomass plants is larger than that
of the trash plants due to the difference in feedstock
cost.
To interest private capital at a 15% rate of return, a
1000 tonne per day plant could pay $30 per tonne of
organics and charge $0.72 per gallon as can be seen in
Figure 10. Examining a 1000 tonne per day plant in more
detail, in Figure 11 it is seen that if the feedstock cost is
S30/tonne and the local wholesale gasoline value is SI.00
per gallon, the projected rate of return would be 31%.
These economic predictions for the process point out
that for the process to be able to buy the organic
feedstock, fairly large plants will need to be constructed.
However, by commercial standards these plants at the
1000 tonne/day size are in reality not very large and
would have an output of a fairly small oil refinery (less
than 2000 barrel per day). [f the 1000 tonne/day
biomass-to-gasoline plant were to be located at the
center of a biomass producing area having an assumed
annual biomass production rate of U.2 tonne/hectare (5
tons/acre), the necessary biomass could be raised within
a 10.2 km radius. Long hauling distances would not seem
to be involved with this process and the gasoline
produced would be consumed relatively locally.
16* RATE OF RETURN
-30
GASOLINE VALUE t/LITER 000
500
too
PLANT S12£. TONN6/OAV
Fig. 10. Biomass-to-Gasoline Economics with Private
Financing
60
x
c
3
c
u.
C
<
€
Z
w
O
c
«
1.90
1.00
Q.flO
0.80
LOCAL WHO LISA Li GASOLINE VALUI. I/GAL
Fig. 11. Rate of Return for 1000 tonne/c!ay Plant
SUMMARY
This process converts organic waste materials into the
basic hydrocarbon building blocks, i.e. the olefins:
ethylene, propylene, and butylene. Although these
compounds could be used as highly valued
petrochemicals, they can also be profitably converted to
a high octane, unleaded gasoline with only a small
amount of fuel and lubricating oils as the by-products.
The process utilizes a high temperature, short residence
time pyrolytic process with steam dilution to optimize
the production of the desired gaseous olefins. This
48
-------
process is virtually identical to that used by the oetro- 5
chemical industry to make ethylene and propylene from
crude oil. Once the gaseous olefins are produced, the
technology required to convert them into gasoline is
state-of-the-art. Experimentation on a 5 !
-------
EMERGING TECHNOLOGY FOR MAXIMUM CONVERSION
OF WASTE CELLULOSE TO ETHANOL FUEL
BY
Charles J. Rogers
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
ABSTRACT
The U.S. Environmental Protection Agency-New York University
scientists have been working over the past five years on continuous
processing technology for industrial-scale conversion of waste cellulose
to glucose. A continuous waste-cellulose to glucose pilot plant with a
capacity of one ton per day has been in operation for approximately two
years. The reactor device is a twin-screw extruder, selected because of
its capacity for conveying, mixing, and hydrolyzing up to 60 percent of
the cellulose values to glucose. In the past, acid hydrolysis reactor
development studies have focused primarily on the conversion of hexosan
to glucose. Agricultural residues and wood also contain a pentosan
fraction that can be hydrolyzed and fermented to ethyl alcohol. This
article reports results of a continuous acid hydrolysis development and
a discussion of a two-stage reactor development to maximize ethanol
production from carbohydrate-bearing waste.
50
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AFB COMBUSTION OF MUNICIPAL SOLID WASTE:
TEST PROGRAM RESULTS
by
L.C. Preuit, Project Scientist, Combustion Power Co.
K.S. Wilson, Project Engineer, Combustion Power Co.
ABSTRACT
Air .classified Municipal Solid Waste (MSW) was fired in an Atmospheric
Fluidized Bed Combustor at low excess air to simulate boiler conditions.
The 7 sq. ft. combustor at Combustion Power Company's energy laboratory
in Menlo Park, CA, incorporates water tubes for heat extraction and re-
cycles elutriated particles to the bed. System operation was stable while
firing processed MSW for the duration of a 300-hour test. Low excess air,
low exhaust gas emissions, and constant bed temperature demonstrated feasi-
bility of staam generation from fluidized bed combustion of MSW.
During the 300-hour test combustion efficiency averaged 99%. Excess
air was typically 44% while an average bed temperature of 1400 °F and an
average superficial gas velocity of 4.6 ft/sec were maintained. Typical
exhaust emission levels were 30 ppm SO2, 160 ppm NO^, 200 pom CO, and 25 ppm
hydrocarbons. No agglomeration of bed material or aetrimental change in
fluidization properties was experienced.
A conceptual design study of a full scale plant to be located at Stanford
University was based on process conditions from the 300-hour test. The plant
would produce 250,000 Ib/hr steam at the maximum firing rate of 1000 tons
per day (TPD) processed MSW. The average 800 TPD firing rate would utilize
approximately 1200 TPO raw MSW from surrounding communities. The Stanford
Solid Waste energy Program was aimed at development of a MSW fired fluidized
bed boiler and cogeneration plant to supply most of the energy needs of
Stanford University.
52
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INTRODUCTION
Disposal of solid waste has historically been an economic cost to
municipalities and industry. The least expensive means of disposal in
this country has traditionally been landfill for which the capital invest-
ment required is minimal. Rapidly decreasing availability of space for
landfill and rapidly increasing need for recovery of the energy value of
solid waste have generated considerable interest in'the development of
solid waste combustion technology. Mass burning incinerators, both with
and without water walls for energy recovery., have seen the greatest use
in combustion of municipal solid waste, particularly in Europe where in-
cineration of solid waste is much more common. Drawbacks of mass burning
include low process efficiency and high emissions levels. Alternative
processes include atmospheric fluidized bed (AFB) boilers, semi-suspension
fired boilers, and pyrolysis processes.
AF3 boilers offer the advantage of low N0X emissions and high combustion
efficiency in relatively compact equipment for the firing of municipal solid ¦
waste (MSW). Prior to the present testing, however, MSW combustion in an
AFB boiler had not been demonstrated. An experimental program was designed
to investigate the favorable operating regimes for a bed with steam-raising
tubes, to determine the combustion efficiency, to measure the gaseous pol-
lutants, to determine the erosion or corrosion of the tubes, and to investi-
gate the fouling of the tubes or system internals caused by the combustion
of municipal solid waste. Two 50-hour preliminary experiments were run
in order to shake down the equipment and to conduct parametric studies to
identify the most favorable operating regime for a subsequent 300-hour test.
This paper will describe the results of the experimental program and relate
those results to the economics of a full scale cogeneration facility being
considered for Stanford University.
EQUIPMENT DESCRIPTION
Testing was conducted in a 7 sq. ft. atmospheric fluidized bed combustor
at Combustion Power Company's energy laboratory. The refractory-1ined
combustor is cylindrical with an inside diameter of 3 ft. and an inside
height of 16 ft. A view port permits observation of the bed during operation.
Figure 1 diagrams the combustor facility as arranged for combustion of
processed municipal solid waste (MSW). Figures 2 and 3 show the combustor
and controls.
The combustor permits several arrangements of in-bed heat exchanger
tubes so that heat extraction can be adjusted to suit desired test conditions.
53
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Ol
4>-
GAS 81
PARTICULATE
SAMPLING
RECYCLE
CYCLONE
FLUID BED
7 FT*
FEED
CONVEYOR
MSW
SUPPLY
BURNER
AIR
AIR
HEATER
GAS
PARTICULATE
SAMPLING
RECYCLE
MATERIAL
SAMPLE
STEAM/WATER
WATER
LIQUID FUEL
MATERIAL
DRAIN &
SAMPLE
FLUIDIZING
AIR
GAS
COOLING
SECTION
u
COOLING
WATER
HI PRESSURE
AIR
EXHAUST
BAG
FILTER
h_t
ASH
Figure 1 Fluid Bed Boiler Test Facility
-------
Figure 2
CTU Fluidized Bed Combustor
at Combustion Power Co., Inc.
C*C GAS
I analyzes *acx
Figure 3
CTU Controls
«ESO«ATE
CONTROL CONTROLLER
I ®uSH8urroNS —
| OIL CONTROL
•ANEL
CTU CONTROLS £
55
-------
Primary neat extraction is through two, three, or roar horizontal water
tube bundles. These stainless steel tubes operate at low temperature to
assure test reliability. Typically, 150 psig water is heated from 200 F to
300 F. This water is flashed to atmospheric pressure and make-up water re-
duces the fsedwater temperature to 200 F. The water tube wall temperatures
are lower than those of typical boiler tubes so that temperature-related
corrosion does not occur. For the long duration test, air-cooled sample
tubes were installed in the fluid bed and in the freeboard above the bed.
These tubes were designed to duplicate boiler and superheater tube-wall
temperatures for study of erosion and corrosion. Figure 4 shows the bed
heat exchanger arrangement for the 300-hour test.
The combustor may be operated with or without recycle of elutriated
bed material. During the first parametric test the exhaust cyclone at
the combustor was arranged to discharge into a collection barrel rather than
returning collected particles to the bed. During the second parametric
test and the 300-hour test, elutriated particles were recycled back to
the bed from the cyclone. Discharge piping from the stainless steel re-
cycle cyclone premits sampling of recycle material during operation.
Exhaust gas from the recycle cyclone passes through a spray cooler
before final particulate clean-up in a baghouse. Stack discharge from the
baghouse meets .all applicable emissions regulations. Sampling ports are
provided before and after the recycle cyclone, and also in the discharge
stack from the baghouse.
Solid Waste Processing and Feed
Municipal solid waste is received in conventional packer trucks, each
containing 3 to o tons of refuse. The trucks dump their contents on a
covered concrete pad from which the refuse is pushed unto shredder input
conveyors as shown in Figure 5. The 100 hp Eidal mini-mill shredder has a
nominal capacity of 5 tons per hour. Shredded solid waste is air-
classified and the light fraction pneumatically transported to a storage shed
to await transport to the combustor facility.
At the combustor a live bottom bin provides short term storage and
variable outfeed capability. Processed MSW is carried from the bin by
the feed conveyor which is designed to provide uniform volumetric flow of
fuel. The' combustor bed temperature control loop adjusts the speed of the
feed conveyor, which discharges into a constant-speed rotary airlock. From-
the airlock fuel is fed pneumatically through a 3-inch feed pipe to the fluid
bed combustor.
Instrumentation
During combustion of processed MSW, temperatures in the system are
monitored at 37 points. Data is collected for pressure and flow of combustion
air, exhaust gas, cooling air and water, ana fuel oil. Exhaust gas compo-
sition is continuously monitored and concentrations of 0?, CO, NOx, and
hydrocarbons are recorded. Gas analysis is supplemented by Orsat testing
56
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VERTICAL TUBE(315°)
HORIZONTAL
TUBES
BED TU8E LOCATION
AIR OUTLET
WATER OUTLET
AIR INLET
(CORROSION SPECIMENS
WATER FLOW SCHEMATIC (HORIZONTAL TU8ES)
WATER
INLET
Figure
SSWEP 300 HOUR TEST
BED HEAT EXCHANGER ARRANGEMENT
57
30-1760
-------
PNEUMATIC
TRANSPORT
•SOLID WASTE RECEIVING
CONVEYORS
LOAOER
SHREDOER
INPUT CONVEYOR
¦.... SOLID WASTE
-REJECT
•' FRACTION „
- CONVEYOR •
3LOWER'
OUTFEED
CONVEYOR
AIR CLASSIFIER^
Figure 5 Solid Waste Processing Station
58
-------
at frequent intervals. Samples are taken daily for determination of HC1
concentration and particulate loading. Material samples for analysis are
taken daily from the bed and from the baghouse.
PARAMETRIC TESTS
Two 50-hour parametric tests were conducted to accomplish operational
checkout of the system, explore the range of allowable process parameters,
ana identify the most desireaole conditions for longer duration steady-state
operation. 3oth parametric tests were planned to explore the same range of
parameters. However, the first test was run without recycle while in the
second parametric test elutriated material was recycled back to the bed.
The first test ran 48 hours before being shut down by high pressures caused
by slag build-up in the combustor freeboard and exhaust duct. The second
parametric test was terminated after 73 hours of operation.
Parametric Test Results
Parametric testing began with the bed depth maintained at 2.5 ft.
(slumped), but freeboard combustion and temperatures were found to decrease
considerably when bed depth was increased to 3 ft. (slumped). Deeper beds
were used for all subsequent testing. Stable bed combustion was maintained
within the ranges of:
Sed Temperature 1300 - 1410 op
Superficial Velocity 4.1 - 6.8 ft/sec
Excess Air1 50 - 74%
2
Combustion efficiency averaged 98.9%. Operation outside these ranges,
particularly-with excess air below 40% resulted in undesireable freeboard
^Excess air is calculated from:
EA = 2.67C +~3H + S - 0 X C02 +°C0 X 1C0?°
where: EA = Excess Air
C, H, S, 0 = Respective Elemental dry weight %
02, CO2. CO = Respective gaseous dry volume %
^Combustion efficiency is based on unburned carbon in the flue gas and ash:
M" a(6HC02^ + if b^HC0^ + ft c^AHh'C^
12 _ . 12 . .~7
-------
afterburning and slag deposits in the combustor freeboard and exhaust ducting.
The 3-inch diameter fuel feed line was found to be very susceptible to
plugging problems caused by round plastic lids of approximately 4-inch
diameter. These' lids were resilient enough to pass through the shredder,
light enough to pass through the air classifier, but just stiff enough to
cause blockage of the pneumatic feed line. Adjustment of the air classifier
eliminated most of the lids and the problem with feedline plugging, but also
resulted in rejection of a larger proportion (near 50°.:) of the shredded MSW
than had been desired. Larger diameter feedlines or improved shredding of
the MSW would eliminate this problem in large scale equipment.
Slag deposits which formed during parametric tests were subjected to
fusion-temperature analysis and found to have initial deformation tempera-
tures of 1990 f and above. Differential thermal analysis confirmed the
fusion test results. Since slag formation thus appeared to be related to
high freeboard temperatures, one process condition set for the 300-nour
test was a freeboard high temperature limit of 1600 F. The slag samples,
analyzed were, in general, calcium-rich alumina silicates.
300-HOUR TEST
Operating conditions for the 300-hour test were based on results- of the
two parametric tests. Test objectives were to:
• Demonstrate the feasibility of burning municipal solid waste
in an atmospheric fluid bed combustor with energy extraction
from the bed.
• Evaluate the fluid bed media and fluiaization characteristics
over a 300-hour time period.
• Characterize exhaust gas emissions
• Measure bed heat transfer coefficients
• ' Gather data on erosion and corrosion of typical boiler and
superheater materials at representative tube wall temperatures.
The 310 hours of operation included 298 hours firing MSW at test conditions.
The test was completed without any significant combustion-related problems,
and operating conditions remained substantially constant. Upsets were
caused by feedline plugs which occurred 35 times during the test. These
blockages, caused by plastic lids which did not shred during fuel processingn
were cleared within 2 to 5 minutes while combustor operation was maintained
on oil. No material deposition or agglomeration was observed; at test
conclusion the combustor and freeboard were virtually free of slag.
60
-------
Fuel Analysis
Samples of the processed MSW were analyzed daily. Fuel properties
were reasonably consistent throughout the test. Results of proximate and
ultimata analysis on the fuel are:
PROXIMATE ANALYSIS
(As Received)
Averaae
Ranae
Moisture Fraction (%)
23.5
17 - 26
Ash Fraction (%)
lO.c
9 - 13
Volatiles {%)
57.5
54 - 54
Fixed Carbon (")
8.2
8 - 9.7
Higher Heating Value (Btu/lb)
5572
5250 - 5050
ULTIMATE ANALYSIS
(Dry Weight %)
Average
Ranae
Carbon
44.46
43.9 -
45.2
Hydrogen
5.96
5.8 -
6.1
Oxygen
34.32
32.2 -
35.6
Hi trogen
0.67
.53
- .80
Chlorine
0.49
.40
- .67
Sulfur
0.13
.09
- . 17
Ash
13.97
12.0 -
16.0
Higher Heating Value (Btu/lb)
7352
6900 -
7700
Operating Conditions
Operating conditions remained substantially constant throughout the
300 hours of test operation although some parameters changed due to a gradual
decrease in bed particle size that occurred during the first half of the test.
As typical steady state operating conditions, data from the last 144 hours
of the test were averaged:
Sea temperature
1392
o_
r
Freeboard temperature
1437
°F
Superficial velocity
4.6
ft/sec
Excess air
44
Of
•'0
Bed depth (slumped, nominal]
3.5
feet
Fluidizing air flow
43.0
1b/mi n
Fuel feed rata
8.2
1b/min
Combustion efficiency
99.0
a'
j:
Exhaust material recycle rate
16
1b/mi n
Sachouse ash collection rate
0.9
1b/mi n
3ed material letdown rate
4.9
1b/hour
61
-------
Figure 6 shows the temperature recorder chart for a portion of the twelfth
day of operation (259 through 256 hours into the test) as representative of
general test conditions. 3ed temperature remains constant, despite fluctua-
tions in freeboard and exhaust temperatures caused by variations in heating
value of the processed MSW fuel. Note that sample time periods for emissions
and gas analysis are identified and that, during two hours of the recorded
period, gas analysis data were being recorded by the California Air
Resources Board (CARB) using their mobile equipment. Satisfactory agree-
ment was found between CARB and C?C data for gaseous emissions.
Flue Gas Emissions
Emissions levels in the flue gas were considered very important to the
basic program objective of demonstrating the feasibility of steam generation
by firing MSW in an AFB boiler. Actual emission levels verified the potential
for low flue gas emissions levels. Average emissions levels for the last 144
hours of test operation were:
Generally, each of the gaseous constituents monitored tended to exhibit
constant variation. Occasional very high spikes of SOj, CO, and hydrocarbons
occurred independently of each other or any other parameter recorded. These
spikes were probably due to particular constituents of the MSW fuel. Emissions
of SO2 and N0X are of particular concern in light of the tight regulations
regarding these pollutants. Actual emissions levels were well under 1979
EPA promulgated New Source Performance Standards (NSPS) for boilers but would
require emissions offset consideration to be approved by California and
local authorities. The indicated exhaust concentrations translate to approx-
imately 0.06 Ib/MMBtu fuel input for SO2 and 0.25 lb/MMBtu for N0X average
for the last 144 hours of operation.
Bed Material
The original bed material was Monterey 16-mesh sand with an average
particle size^ between 1.0 and 1.1 mm. Daily samples were taken of bed
material and of material returning to the bed from the recycle cyclone.
Figure 7 shows the rapid drop in bed particle size at the beginning of the
^Particle size is calculated by the "Mean Specific Surface" method (1)
Flue' Gas Emissions
02
5.7 %
13.5 %
200 ppm
29 ppm
160 ppm
40 ppm
Hydrocarbons (as CH4)
62
-------
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SSWEP NO. 3 TEST
AUGUST 29, 1979 j
259 THRU 266 HOURS FROM
:
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-C-
E
E
Hi
M
ci
IU
-J
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tc
<
a.
IU
0
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EC
(U
>
<
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0.8
0.7
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0.5
0.4
0.3
0.2
0.1
* lici.yi.je.
Mean Specific Area
• Be J Material,
Mean Specific Area
1 1 I I I _l I I I
6 7 a 9 10 11 12 13 14
CALENDAR DAY
Figure 7
-------
test, followed by a more gradual decline to nearly constant particle size
at the end of the test. Also shown is the recycled material size which
appeared unaffected by the changing bed material size. Some pieces of glass
could be observed in the material samples and a few (less than 1%) pieces
of agglomerated particles up to h" size.
Daily bed material samples were analyzed for cations and metals content
by means of the emission spectroscopy scan method. The concentrations of
the major constituents of the bed material were found to remain essentially
constant. A number of elemental concentrations, however, increased through-
out the test and accumulation of these materials appeared to be continuing
up to the time the test was terminated. This accumulation of elements was
the only observed phenomena which had not reached a steady state equilibrium
before the end of the test. Longer test duration will be necessary to observe
the effects of this accumulation. Elements which accumulated were Ca, Fe,
Mg, Ti, Na, Cu, Mn, P, Zn, and possibly Pb. Concentrations of these elements
are shown for samples taken early in the test and at the end of the test
(Trace elements are not shown):
Concentration Weight %
Element
Third Day
Twelfth Day
Si
37.0
33.8
A1
4.0
3.8
Ca
1.8
5.5
K
2.8
2.7
Na
1.9
4.0
Fe
0.48
1.2
Mg
0.17
0.69
Ti
0.068
0.28
Ba
0.11
0.10
Heat Transfer
Water inlet and outlet temperatures as well as flow through the main
heat exchanger were monitored throughout the test. That heat exchanger con-
isted of two four-pass, horizontal tubes arranged in the bed as shown in
Figure 4. Early in the test, the overall heat transfer coefficient averaged
46 3tu/nr-ft--F. 3y the end of the test, the heat transfer coefficient had
increased to 58 3tu/iir-ft2-F. The increase in heat transfer coefficient is
attributed to the decrease in bed material particle size. The influence of
particle size on outside wall heat transfer coefficient is predicted by
Bashakov {I) or Locke (3_).
Corrosion and Erosion
In addition to the stainless steel (TP316H) water cooled tubes in the
bed which were the primary means of heat extraction, air cooled sample
tubes were installed in the bed and in the freeboard to duplicate wall
65
-------
temperatures of superheater tubes. No significant corrosion or erosion
was observed on the water cooled tubes in the bed. Mechanical failure of
the air cooled tube in the bed invalidate its exposure as a tube sample.
The freeboard air cooled sample tube was installed to transverse gas
flow in the exhaust ductwork from the combustor. The tube was fabricated
from sample sections of six different tube materials. The samples were
exposed to 1500 F - 1600 F flue gases heavily laden with particulate
(40-50 gr/acf) at a gas velocity of about 35 fps. The sample tube wall
temperature was about 720 F. Combined corrosion and erosion resulted in
substantial metal wastage of carbon steel specimens, with less wastage
apparent as the alloy content increased.
As shown in Figure 8 and Table I, metal wastage was greatest for carbon
steel coupons, approximately 50-60% of the wall facing the gas side, while
wastage of the sides and tops was less than 5«. Wastage was considerably
less for the low alloy steels in the same orientation. On the side facing
the gas flow, the wastage was 13-172 while elsewhere it was less than 3%.
The metal wastage of the austenitic specimens (SS304, SS316, and Incoloy 825)
was the lowest, being less than 6% on the side facing the gas flow and less
than 1% elsewhere. Scaling and deposits were also orientation dependent,
with bottoms of the coupons relatively free of scale and deposits compared
to the sides and top. As expected, scale formation was thickest on the
carbon steels, and the chrome-containing austenitic steels were resistant
to scaling.
Residual corrosion penetration was very low on the bottoms of the
carbon steel and low alloy specimens. Apparently, corroded areas and scale
were removed by erosion as they formed, i.e., corrosion-erosion was a
major factor in the metal wastage. Corrosion penetration on the low alloy
specimens was comparatively low on the tops and sides at 5 - 10 microns.
With respect to corrosion under the exposure conditions, the low alloy
specimens compared well with the type SS316 that showed only 5-10 microns
of corrosion penetration, while the metal wastage of the low alloy specimens
was greater. The SS304 and Incoloy 825 showed corrosion penetrations ranging
from 10-50 microns. Apparently, corrosion was by oxidation and sulfidation
as sulfur was found in most corroded regions of all coupons.
CONCEPTUAL DESIGN STUDY
An economic study was undertaken to determine the promise of the AF3
boiler system as defined by the results of the experiments. The complete
coaeneration system was envisaged for application to the Stanford University
campus with the sizing and performance of the MSW fired AF3 boiler based on
test results. While the application at Stanford University might not have
been the most favorable one, it was regarded as a typical situation and that
there would be considerable benefit in having a study made to meet realistic
reaui rements.
66
-------
GAS FLOW
SPECIMEN
IDENTIFICATION
7A7
Nfc^Cr-Mo-Cu
INCO 325
St>163
6A6
16Cr-12Ni-2Mo
SA-312-TP316H
SA-213-TP-316H
5A5
18Cf-3Ni
SA-312-TP304H
SA-213-TP-304H
4A4
2'
-------
TOP
SSWEP: 300 MR TEST COUPONS
. LOCATION: CTU FREEBOARD
TABLE I PIPE THICKNESS ANO MICROGRAPH MEASUREMENTS
GAS STREAM
(Residual Maximum]
Specimen
Pipe Thickness
Micrograph
Pipe
(Inch)
V
3
Measurements
S
ica le
Penetra-
Garments
Identification
Orientation
Unexposed
Exposed
wastage
tion M
IA1
1. Bottom
.115
.060
47.3
None(a)
6
(a) Corrosion-
erosion
(Carbon 5tee!)
2. Left
.112
.113
-.9
15
10
Side
(SA-106B)
3. Top
.110
.116
-5.5
16
60
(SA-210AI)
¦4. Ri gh t
.113
.110
2.7
(b)
14
(b) Spalled
Side
3A3
1 .
.116
.100
13.3
3
<2
(1 !iCr-4 Ho-Sr)
2.
.115
.116
-.9
cG
10
(SA-335P11)
3.
.118
.124
-5.1
15
10
(SA-213T11)
4.
.120
.117
2.5
250(a)
1G
(a) Scale and
ash de-
posit
4A4
1.
.135
.113
16.3
30
<2
(2>sCr-l Mo)
2-
.130
.125
.3
a.
5
a. Spa lied
(SA-335P22)
3
.129
.131
-1.5
b.
10
b. Spa lied
(SA-213T22)
4.
.132
.132
0
c.
5
c. Soalled
5A5
1.
.105
.100
4.3
-
35
.005" wastage
(18Cr-3Ni)
2.
.105
.105
0
100(a)
50
(a) Scale ana
ash de-
posit
(SA-312-TP304H)
3.
.105
.106
-1.0
(b)
10
(b) Spa 1 led
(SA-213-TP-304H)
d.
.104
.104
0
200(c)
10
(c) Scale and
ash da-
DOS i t
6A6
1
.107
.101
5.5
3
-
.006" wastage
{16Cr-l 2Ni -2Mo)
12
.118
.113
0
30
10
(SA-312-TP316H)
! 3
.107
. 107
0
a.
-
a. Spa 1Tad
(AS-213-TP-316H)
4
.106 '
.106
0
b.
5
b. Soalled
7A7
1
.112
.109
2.7
20
30
.003" wastage
(Ni-Fe-Cr-Mo-Cu)
2
.113
.113
0
a.
30
a. Spa 11ed ?
(INCO 325)
3
.117
.117
0
b.
4
b. Spalled ?
CSb-163)
4
.118
.119
-.3
c.
25
c. Ash cie-
30S i t
Unexposed pipe remnant measurements.
68
-------
Proposed System
The AFB system for study was designed to meet an existing situation
in which the local municipality is faced with unavailability of landfill
disposal area while Stanford University is seeking to control energy costs.
Municipal solid wast? would be processed at a central collection location
and the MSW fuel trucked to the campus boiler plant. Size of the system
is specified by the 800 tons per day of processed MSW estimated to be
available in 1983. The modular AF3 boilers would produce 600 psia, 750 F
steam for a turbine with extraction at a pressure of approximately 170 psia.
The extraction steam would condense in a heat exchanger to provide heating
and chilling steam for the campus, Steam not needed for caucus services
would flow through the condensing stage of the turbine. Thermodynamic ana
process studies provided estimates that the proposed system would supply
all of the university steam demand and approximately 50* of the electricity
needs.
A flow-diagram of the proposed system is shown in Figure 9. No attempt
was made to investigate the. processing of the MSW; study was limi-ted entirely
to conversion of the processed MSW to thermal energy and to electricity. All
ancilliary equipment necessary for energy production from MSW fuel was in-
cluded.
Plant Design and Cost Estimating
The plant design was broken down into 12 major components listed below:
1.
Boiler system
2.
Start-up system
3.
Combustion air system
4.
Flue gas system
5.
Bed-maintenance system
5.
Flyash-disposal system
7.
Fuel-feed system
a.
Fuel receiving and storage
g.
Main steam system
10.
Feed-water system
11.
Electrical and control system
12.
Buildings and site
For each of these systems, sufficient design work was done to define a concept
ana to specify the necessary size of the equipment. Wherever possible,
standard components were used and cost estimates obtained from vendors. A
plant plan, Figure 10, and laycut drawings were made and necessary buildings
included to enclose turbine, boiler, and fuel receiving areas so as to be
compatible with the campus site. No cost was included for the value of the
land. Table il lists the major cost components along with the principal
items contr*butino to the cost. An artist's rendition of what the plant
might look like is shown in Figure 11 and general performance figures for
the plant are shown in Table III.
69
-------
lUHblNt
fcXFHACIiON
irAfifc
CONDENSING
ilACt
iltClHlCAL
COnOCNSATC
ihom s.u.
tXCilANGtH
rtCDWAI tH
O
PMlMARV tXllAUSI
ClEANUP
INDUCED OflAf I
fcKMAUSTCA&
\7
TIMPOHAHY
JIOHAGE AHiA
^~L
o o oo
fCfOtVAIEH
OO
COMUUSTOa
ASH
Aifl
fcOliO WA<
fiiU CONVfYOHS
COUUUSUON
AIR OLOM£A
fE£0 ttUJWtKS
ilTDOMM MAKCUf
Figure 9 Stanford Solid Waste Energy Plant Flow Diagram
-------
310
-CZO] E==
TURBINE BLDG.
FUEL RECEIVING BLOG.
BOILER BUILDING
ASH SILO
SAND SILO
COOLING TOWERS
RESERVE FUEL
TANK
Figure 10
SITE PLAN
STANFORD SOLID WASTE ENERGY PLANT
-------
Hoi lor System
Modules w/tubes & plenums
Itecyc Lc cyclones (2^>)
Exhaust manifolds (2)
Evaporators (2)
Economizers (2)
Attomporacors (2)
S111»jioitii & lagging
Scolli lowers (6)
Start-up System
Duct-burner assembly
llooster fan
Fuel-oil pumps (dual)
Fuel-oil storage tank
lied Injectors (36)
Air manifold & dampers
Combust Ion Air System
F.I). fans 4 motors (2)
InLake silencers (2)
Tubular air preheaters (2)
Dm: twork
I I iiij-C.'ns System
M
-------
Table III
PLANT PERFORMANCE
• Design Firing Rate for Processed MSI.1 Fuel:
Average - 800 tons per day
Maximum - 1000 tons per day
• Yearly Average Plant Output
Steam at 125 psi, 110,800 Ib/hr
Electricity -6.7 MW
i Soiler Output: Steam at 600 F, 750 psi
Average - 200,000 Ib/hr
Maximum - 250,000 Ib/hr
t Maximum Electrical Output (net) 13.8 MW
Concurrent 125 psi steam output 91,200 Ib/hr
• Fuel Storage: Normal: 200 tons (6 hrs average output)
Maximum: 500 tons (15 hrs average output)
• Reserve Fuel: Low-grade bunker oil - 35 GPM at maximum output
t Reserve Fuel Storage: 126,000 gal, 3 clays
73
-------
BOILER BUILDING
TURBINE BUILDING
STANFORD SOLID WASTE ENERGY PLANT
STEAM - 250.000 LBS/HR MAXIMUM
ELECTRICITY - 13.8 MEGAWATTS MAXIMUM
WASTE FUEL 800 TONS PER DAY AVERAGE
FUEL RECEIVING BUILDING
-------
Environmental Considerations
Emissions data collected during the 300-nour test were converted to a
pounds per hour basis using the flow rate of combustion products for an 800
tons per day plant. Below are the data reported in this form, together
with the "offset" that Stanford is permitted to take if it shuts down its
present oil-fired heating plant.
Emission Projected 800-TPD Plant Offset from Existing Plant
Only CO would exceed the offset available from the existing boiler. The
present boiler figures are based on steam generation at the rate of 80,000 Ib/hr
whereas the AF3 plant figures are based on 800' tons per day fuel corresponding
to 110,000 lb/hr of steam plus' an average of 6.7 MW of electrical power. Thus
the AF3 boiler is nearly 40« larger than the present boiler and the emission
levels are very similar. It appears that fluidized bed combusitan of MSW
is a sufficiently clean process that there would be little difficulty in
meeting the stringent requirements of the San Francisco Bay Area Air Pollution
Control District when the offset from the present boiler is considered.
Economic Summary
Cost estimates for the proposed full scale system are summarized in
Table IV. Each major subsystem is shown, along with the additional costs
which are recommended for a construction project such as this by the standards
of the Electrical Power Research Institute. The total direct cost as esti-
mated is 16.7 million dollars, and the total plant investment, using various
contingencies and sales tax, amounts to 23.1 million. This figure should
be compared to plants which handle 1200 tons per day of raw municipal solid
waste and produce both steam ana electrical power. The costs presented do
not include processing or transporting the processed MSW to the point of use.
CONCLUSIONS
Successful completion of the 300-hour test demonstrated the feasibility
of fluidized bed combustion of municipal solid waste to generate steam.
Necessary conditions for steam generation were met:
1. Operation at reasonably low excess air (44%) for porcess efficiency.
2. Constant bed temperature (±20 F) for controllable system output.
3. Freedom from slag and its associated problems.
4. Low exhaust gas emissions for environ-enta1 acceptabi1ity.
2.9 lb/hr
24.1 lb/hr
Hydrocarbons
7.7
8.9
0.7
23.1
5.2
1.1
75
-------
Table IV
STAFFORD SOL I 0-'.'ASTE ETIERGY PLANT
Total plant investment
1. 3oiler system S 2,239,700
2. Startup system 155,200
3. Cornbustion air system 793 ,900
4. Flue-gas system 2,382,000
5. 3ed-i-aintenance system 34,100
6. Flyash-disposal system 79,200
7. Fuel-feed system 457,300
3. Fuel-receiving bldg., equipment 252,400
9. Main steam system 5,421,000
10. Feedv.-ater system 1,942,500
11. Electrical/control s/misc. 1,204,100
12. 3uilding, sitework, construction, A S : 1 ,545 ,000
Total Oirect Costs 16,552,000
Undistributed Costs (6") 999,700
Process Capital 17,551,700
Engineering ¦£ Heme Office Fees 1,555 ,700
Subtotal 19,327,900
Project Contingency (Subtotal x 15.") 2,339,200
Process Contingency (Item 1 x z%) 112,000
Sales Tax 777 ,300
Total Plan: Invest-ant 23,115,-00
76
-------
These conditions were met in a long-duration test designed to reveal any
process problems likely to develop.
Bed material characteristics after long term operation will depend on
the source and preparation of the solid waste fuel. Early in the 300-hour
test the average bed particle size decreased significantly although it
subsequently appeared to reach equilibrium. The elemental composition of
the bed was still changing after 300 hours. Neither situation caused any
detrimental change in bed fluidization properties nor were emissions
affected. It was concluded that the overall heat transfer coefficient for
the bed tubes increased due to to the decrease in bed material size.
Sample tubes exposed to a high velocity flue gas stream with high
particulate loading experienced substantial metal wastage. Alloy steels
would be suitable for service if protected from abrasion but none of the
samples tested would be suitable for long term service under test conditions.
Conveying air in the .fuel feedline constitutes a significant (30")
portion of the total combustion and fluidizing air. This air enters the
bed as a point source and is not easily distributed throughout the bed.
While a larger feedline is desireable to avoid feedline plugging and permit
firing of more coarse fuel, greater spacing between larger feedlines may
create air distribution problems in the bed. Investigation of alternate
fuel feed technology is warranted.
Based on data from 300 hours of testing, projected emissions from an
AF5 boiler firing municipal solid waste would be low compared to a existing
conventional oil fired boiler. Total plant investment for a coaeneration
plant burning 800 tons per day of processed MSW fuel would be S23,115.000,
corresponding to approximately SI,150/kw if the entire steam output were
converted to electricity.
77
-------
ACKNOWLEDGEMENT
This work was accomplished at Combustion Power Company, Inc. under
sub-contract to Stanford University with the program jointly sponsored
by the United States Environmental Protection Agency and Department of
Energy. The generous contribution of Professor R.H. Eustis of Stanford
University is gratefully acknowledged.
78
-------
REFERENCES
1. Kunii, 0., and Levenspiel, 0., "F1uidization Engineering", John Wiley
and Sons, 1979.
2. Bashakov et.al., (1973). Powder Technology, pp. 8, 273.
3. Locke, M.S. et al, "Fluidized Combustion in Great Britain", paper
presented at Fourth International Conference on Fluidized Bed Combustion,
Mitre Corporation, McLean, Virgina, December 1975.
4. Vander Molen, R.H., "Fluidized- Bed Combustion of Solid Wastes", Presented
at the Symposium on Thermal Conversion of Solid Waste and Biomass,
American Chemical Society Meeting, September 1979, Washington, D.C.
79
-------
EVALUATION OF THE AMES SOLID WASTE RECOVERY SYSTEM
Joensen, A.W.
Hall, J.L.
Even, J.
Van Meter, D.
Adams. S.K.
Gheresus, P.
Engineering Research Institute, Iowa State University, Ames, Iowa 50011
EPA CONFERENCE
WASTE TO ENERGY TECHNOLOGY UPDATE
Cincinnati, Ohio
April 15-16, 1980
80
-------
INTRODUCTION
The Cicy of Ames, Iowa has been commercially operating a Solid Waste
Recovery System since November, 1975. This system processes municipal and
commercial solid wasce Co recover refuse derived fuel (RDF) and ferrous
mecals. This solid waste recovery system consists of chree major subsys-
tems; a nominal 150 ton/day process plane, the 500 con Adas storage bin
and che chree coal fired steam generators at che existing municipal power
plant.
Conceptual design for che system operacion specified burning RDF with
coal in a 35 MW tangencially fired pulverized coal fired boiler (unit Mo.
7) at firing races up to 207. or 8 cons/hour. Initial operation in October
1975 resulted in a high dropout of unourned material into che boccom ash
hopper. The power plane chen began burning RDF with coal in che 7.5 MW or
che 12.5 MW spreader stoker boilers. The problem of high unourned material
dropouc in che 35 MW unic was solved by che inscallacion of a Combustion
Engineering Company dump grace at che furnace boccom. This modification
was completed by May 1, 1978, and RDF has been successfully burned in this
unit since chat time.
A three year evaluation of Che Ames Solid Waste Recovery System was
funded by che Environmental Protection Agency and che Department of Energy
with addicional support provided by Iowa SCate Universicy and che American
Public Power Association. Detailed resulcs of che scoker performance and
process plant operacions have been reporced previously [1,3,^,5,9].
Resulcs of che unic No. 7 emissions evaluation is given in [3] while the
total system study for year III is given in [7]. The inability of che
process pianc to initially remove ground glass and other fines resulted in
extreme erosive wear at che process plane, Atlas bin and all of the pneu-
matic cransport lines and in boiler slagging. This problem was solved by
the installation of a double set of a disc screen fines removal syscem in
October-December 1978. This modification and some process plane operacional
resulcs are discussed in (2,7].
This paper presencs some important results obtained from this chree
year syscem evaluation.
PROCESS PLAiNT
A derailed descripcion of che process plant is given in [1,2,5,7].
The material processed and materials recovered are listed in Table 1. The
improvement in RDF quality due to che disc screen inscallacion is shown in
Table 2. Nec coses per con for 1976, 1977 ana 1973 were S1&.27, Sll.ii
and S11.31 respectively.
RDF ana mecai sales for 1978 constituted 7^.37% and 13.53% of cocal
income. Electric energy consumption for 1978 is 63.17 khr/'ton.
31
-------
POWER PLANT
Stoker Fired Boilers No. 5 and Mo. 6
Selected emissions from boilers No. 5 and 6 are listed in Tables 3 and
4. The coal contained a large number of fines which resulted in high parti-
culate emissions. After the installation of new mechanical collectors in
July 1979, along with cutting out of reinjection backpass fines and the
increase of front overfire air, subsequent private tests indicated the
reduction of stack particulate on coal only and coal plus RDF firing. This
latter result was also due to the disc screen installation.
Pulverized Coal Fired Unit No. 7
The installation of the dump grate resulted in the successful burning
of RDF with coal. Selected emissions are listed in Table 5.
Combustion air to the furnace is supplied by secondary air from the
air heater discharge, primary air from the pulverizer, cold undergrate air
supplied from a separate fan, and cold overgrate air entering at each end
through open observation doors, and the two diagonally opposed RDF transport
lines which supply 1.67 m^/sec (3539 ft^/min) of cold air through the air-
lock feeder at the Atlas bin. Undergrate air was 1.70 mVsec (3603 ft^/min)
and overgrate air flow was 0.94 m^/sec (2000 ft^/min).
Excess air at 80% steam load (based on fuel ultimate analysis) varied
from 41.9% for coal only firing to 41.7% at 20% RDF nominal heat input.
At 100% steam load the excess air varied from 42.5% for coal only to 34.6%
at 20% RDF heat input firing.
At 80% steam load, the boiler efficiency decreased linearly from
84.4% (ASME Heat Loss Method) at 0% RDF to 81.1% at 20% RDF firing and
these efficiencies include a manufacturer 1-1/2% unaccountable loss. The
air heater outlet flue gas cemperature increased from 181.1"C to 422aF.
At 100% steam load, the boiler efficiency decreased from 84.35% at
0% RDF to 83.02% at 20% RDF firing. The air heater outlec flue gas temper-
ature increased from 191.7°C to 198.9°C.
At 80% steam load the bottom ash flow rate varied from 64 kg/hr at 0%
RDF to 218 kg/hr at 20% RDF input. At 100% steam load, the bottom ash
varied from 134 kg/hr at 0% RDF to 821 kg/hr at 20% RDF input. Likewise,
the percent heat loss in bottom ash never exceeded 0.2%.
Thus, the installation of the bottom dump grates in the 35 MW pulver-
ized coal boiler allowed for the successful burning of RDF with coal.
ACKNOWLEDGMENTS
The summary data presented above were obtained from a research project
performed by the Engineering Research Institute of Iowa State University
through funds provided by IERL/EPA, Cincinnati, Ohio. Analysis of labora-
tory samples collected was performed by the Ames Laboratory/DOE through
support by the DOE. Technical support and assistance was provided by the
Midwest Research Institute. The generous support of the City of Ames is
also greatly appreciated.
82
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Table 1. Refuse Processed and Materials Recovery
Year
Raw Refuse
RDF3
Metals
Rej ects
Ocher Material
Processed
Produced
Recovery
(Mg)
(")
(7.)
(%)
(Z)
1976
37,252
84.2
7.00
7.5
1.30
1977
44,027
34.54
6.22
8.87
0.39
1978
34,216
84.26
6.31
9.39
0.04
a3y mass difference
Table 2. RDF Characceriscics 3efore and Afcer Disc Screen Installation
RDFa
Before
After
Higher Heating Value - 3TTJ/lb
4904.9
6103.3
(kJ/kg)
(11,408.7)
(14,209.1)
Proximate and Ultimate Analysis, 7.
Ash
20.99
9.55
Moisture
22.06
13.42
Fixed Carbon
30.79
56.10
Volatile Matter
26.16
15.93
Carbon
00
ui
36.67
Hydrogen
6.35
7.42
Nitrogen
0.39
0. 34
Oxygen
42.75
45.62
Sulfur
0.34
0.19
Chloride
0.23
0.21
"Comparative Sampling Period Jan--Mar
83
-------
T.ihi c ). SKMiCTKD EMISSIONS FROM HOILF.K UNIT 5
Parameter (units)
Particulates (controlled) (g/MJ)
p.-rticulates (uncontrolled) (g/MJ)
Oxides of sulfur, S0X (g/MJ)
Oxides of nitrogen, NOx (ing/MJ)
Chlorides (ing/MJ)
Fo rma 1 de y hde (mg/MJ)
Hydrocarbons (ing/MJ)
80% load
1976 Iowa coal with
OX RDF 20Z RDF 50% RDF
807. load
1977 lowa/Wyoming coal with
07. UDF 201 RDF 50X RUf
0.7 i 0.5 0.4 i 0.0 0.3+0.1
3.6i0.6 4.110.2 3-410.2
2.3 l 0.0 1.9 1 0.2 1.5 i 0.6
80.0 ±25-0 76.0 t10.0 64.0 +17-0
13-0 ± 3-0 68-0 i 8.0 97.0 143.O
0.2 t 0.3 0.2 t 0.1 4:3 1 4.1
0.221 0.13 0.171 0.07 0.191 0.08 0.081 0.06 0.09* 0.04 0.071 0.03
O.fl 10.2 0.910.1 1.0 1 0.2
3.2 1 0.5 3.8 1 0.3 4 .2 l 0.9
1.0 i 0.3 0.7 1 0.2 0.9 i 0.4
77.0 1 6.0 67.0 1 6.0 69.0 il3-0
6.5 i 0.7 87-0 121.0 139-0 142.0
11.7 118.2 3.7 11.9 3.4i3.1
Parameter (units)
60% load
1976 Iowa coal with
07. RDF 20% RDF SO'/. RDF
Particulates (controlled) (g/MJ)
Particulates (uncontrolled) (g/MJ)
Oxides of sulfur, SO
Oxides of nitrogen,
Chi or ides
Forma 1 deliyde
Hyd roc a rlions
x
NO.
(g/MJ)
(mg/MJ)
(mg/MJ)
(mg/MJ)
(mg/MJ)
0.9 i 0.5
3.2 1 0.5
1.3 i 1.0
99.0 112.0
22.0 <12.0
2.7 l 2.7
0.151 0.08
1.1 l 0.6
4.4 l 0.6
2.3 1 0.5
104.0 1 8.0
58.0 H7.0
3.1 1 3.3
0.191 0.08
1007. load
19 76 Iowa coal with
OX RDF 207. RDF
505: RDF^V
1..3 1 0.7
3.5 l 1.4
0.8 1 0.4
78.0 120.0
100.0 155.0
6.2 1-8.1
0.311 0.12
1.3 1 0.9
4.1 1 1.1
2.4 i 0.0
81.0 117.0
7.0 l 0.0
3.3 1 3.6
0.09l 0.06
0.4 1 0.I
2.2 1 0.8
2.0 1 0.3
76.0 117.0
62.0 i22.0
2.0 1 2.8
0.151 0.06
^]y
0.4 i
3.1
1 . 7
50.0
101 .0
0.2
0.17
0. 1
1 . 3
0.3
8.0
21 .0
0.1
0.01
two runs at this load and % RDF were accomplished.
-------
¦Vul.le A. SKI.liCTtll I-IHISSIONS FKOM HOII.IX UNI T 6
I'ai ameter (unite)
Pari iinlaleb (nun hi 1 I ed )
I'n r i 1 cu 1 a t ts (uncont ro I 1 ed)
Oxides of sulfur, S0X
Oxides of a 11.rugeii, ll(lx
f'li lor ides
Fo r ma I <1 e It yd e
11 y <11' oca r lioiku
BOX load
1976 1 oua/l'yoin I ng coal wlt:l»
OX HOF 201 RDF 501 HDF
BOX load
(b/mj)
(iiiy/MJ)
(nig/HJ)
(mji/M-l)
(mfc/MJ)
0.5i0.I
2.510.7
0.8! 0. 5
1 33.016.0
6.3J3.2
5 . B19. 0
0.7 i0.2
3.510.3
0.310.0
131.015.0
AA .0*5.0
0.6!0.1
0.91
A .At
0. A i
106.01
0.1
0.9
0./.
3.0
BU.013 3.0
1 .61 0.1
197 7 1owa/WyomLog coal
02 HUF ±' 50Z
w I r It
•a/
km
o.a
l .0
0.9
91.0
9./.
16.0
10.1
10. 3
10.
16.
11 ,
15
0.0710.00
1.9 i 0.1
3.9 l 0.2
0.6 i 0.1
00.0 i 5.0
110.0 i L 5.0
20.0 l 0.0
0.131 0.06
Parameter (unity)
I'a r I: I <• n 1 a I ea ( mill in I I f:d)
Pari Icnlales (unfoni ro I 1 ed )
Oxide:; of sulfur, -S0K
Oxides of nil inguii, N0X
Clil or Ides
I'orma I ili;liyde
llyd roc a r lie n s
(fc/H.I)
(b/hj)
(g/MJ)
(lllg/lil)
(in^/MJ )
(iub/M-I)
(ing/M.I)
60% load
197 7 I owa/Uyom I ng coal ultli
OX I IDF 201 K OF 507.RDF
0.7 i 0.1
2.0 i 0.A
1.A l 0.2
106.0 iI I.0
A.2 i 1.1
2 2.0 112.0
O.Ofli 0.OA
1.8 1 O.A
3.7 1 O.A
O.fl 1 0.1
52.0 110.0
96.0 112.0
20.0 l 7.0
0.071 0.00
i^Only
1 . 7
0.2
A. 3 i 0.3
0.5 i 0.0
96.0 1 A.0
127.0 132.0
2 3.0 117.0
0.07! 0.01
I wo runs at tills load and 'L ItUF were nccoiti)>l I sited.
-------
Table 5. Selected Emissions from Boiler Unit 7
Prior to Installation
of Dump
Grates 1976,
1977
Parameter
Un it s
60%
Load
80%
Load
100%
Load
0%
RDF
0%
RDF
0%
RDF
10%
RDF
Particulates
lb/1.06BTUb
0.23
(0.07)a
0.35
(0.12)
0.60
(0.09)
0.53
(0.12)
(controlled)
£
Part iculates
lb/10 BTU
9.05
(1-02)
7.49
(1.72)
8.26
(0.05)
8.35
(0.30)
(uncontrolled)
c
Oxides of Sulfur
lb/10 BTU
2.61
(0.40)
2.88
(0.70)
3.70
(0.16)
2.88
(1.14)
SOx
c.
Oxides of Nitrogen
NO*
lb/10 BTU
0. 32
(0.03)
0.26
(0.09)
0.35
(0.02)
0.27
(0.04)
ilUA
Chlorides
lb/10qBTU
5.14
(3.75)
13.6
(8.42)
28.14
(6.91)
7.65
(5.05)
Formaldehyde
lb/lOgBTU
4.56
(5.58)
20.9
(44'.0)
5.49
(A. 58)
60.0
(52.6)
Methane
lb/10 BTU
0.00
(0.00)
0.00
(0.00)
0.00
(0.00)
0.00
(0.00)
After Installation of Dump Grates 1978
Parameter Units 80% Load 100% Load
0% RDF 10% RDF 20% RDF 0% RDF 10% RDF 20% RDF
,-itos ih/in6KTI' n.?1 (0.05) 0.17 (0.09) 0.37 (0.07) 0.4? (0.21) 0.A4 (0.07) O.ST fn.ng)
^V-VJIILLUJ. itU J ,
Particulates lb/10 BTU 6.54 (1.33) 7.63 (0.63) 8.21 (1.21) 7.93 (3.58) 7.28 (0.53) 7.47 (0.53)
(uncontrolled)
Oxides of Sulfur lb/10 BTU 3.42 (0.14) 2.84 (0.16) 2.33 (0.63) 3.30 (2.07) 2.33 (0.49) 1.93 (0.51)
SOx
Oxides of Nitrogen lb/10 BTU 0.39 (0.02) 0.33 (0.02) 0.33 (0.03) 0.31 (0.04) 0.26 (0.01) 0.26 (0.03)
Chlorides lb/lO^BTU 10.7 (1.77) 50.9 (35.8) 93.7 (8.96) 7.65 (1.88) 58.4 (31.9) 28.6 (9.35)
Formaldehyde lb/1.0 BTU 8.37 (14.0) 12. (207.) 0.77 (0.42) 0.19 (0.33) 1.44 (0.72) 0.42 (0.19)
Methane lb/10yBTU 5.30 (2.65) 6.07 (1.58) 3.77 (0.30) 3.35 (0.93) 4.58 (1.44) 2.47 (0.58)
avalues in parentheses are + one standard deviation
^to convert from lb/10^BTU to micrograms/Joule, multiply values in the above table by 0.430
-------
TEST FIRING REFUSE DERIVED FUEL
IN AN INDUSTRIAL BOILER
EPA GRANT NO. R806-328-010
GARY L. BOLEY, P.E.
PROJECT MANAGER
CITY OF MADISON, WISCONSIN
In 1979 the City of Madison and the investor owned utility, Madison Gas
& Electric Company, jointly implemented a prepared refuse derived fuel (RDF)
energy recovery project. The City of Madison owns and operates a solid waste
processing plant to process municipal solid wastes for the production of the
RDF. The Madison Gas & Electric Company utilizes the RDF in two Babcock and
Wilcox 50 megawatt pulverized coal boilers.
In the fall of 1978 the City of Madison in cooperation with Oscar Mayer
& Company were recipients of an Environmental Protection Agency Research Grant
to test fire RDF in an industrial boiler. The Oscar Mayer & Company could
represent a second market to the City for the use of RDF.
The industrial sector is a potentially large, user of prepared solid wastes
as a supplemental fuel source. Industrial boiler installations are not able to
take advantage of the highly favorable fuel price advantages that utilities can
obtain, due to their high volume consumption. Therefore, industrial users may
be willing to pay a higher price per unit of energy for RDF than utilities.
Research Purpose
The purpose of the research is to investigate the feasibility of cofiring
municipal solid waste with fossil fuels to determine:
1. Industrial boiler operational performance when cofiring coal and RDF
at various boiler loads and feed rates to determine optimum operating
conditions.
2. Air emissions and performance of existing mechanical air cleaning
system when cofiring coal and RDF.
3. Operational characteristics of the RDF feed system and the reliability
and practicality of receiving, storing and firing RDF at an industrial
operation.
4. Economic analysis of utilizing RDF at an industrial operation.
Project Participants
City of Madison
The City's grant responsibilities, in addition to providing the RDF, include
overall project management, detail design of the RDF receiving facilities and
overall project coordination.
88
-------
Oscar Mayer & Company
Oscar Mayer St Company operates a meat packing plane in Madison. As parr
of their plane operations, Oscar Mayer operates a power plane for the cogenera-
tion of process steam and electricity. One of two Wicks 125,000 pound per hour
boilers will be retrofitted for 3DF firing. In addition to providing the
boilers, Oscar Mayer will also operate the RDF receiving and firing facilities.
M. L. Smith Environmental
M. L. Smith Environmental was retained by the City to provide special con-
sultant services to provide technical direction and staff assistance in the
Engineering evaluation of 3oiler Mo. 5 to determine the method of SUP firing,
assistance in the preparation of the necessary documents for the boiler retrofit
work, develop the RDF receiving and feed process concept and system layout,
provide assistance in the test program development, and assist' in the prepara-
tion of the project's final report.
University of Wisconsin-Madison
The University of Wisconsin-Madison, contracted by the City, will provide
the facilities and personnel necessary for all sampling, data collection,
analysis, and prepare all technical evaluations and reports.
Existing 3oiler Conditions and Modifications
Oscar Mayer & Company's Boiler Mo. 5 is a Combustion Engineering, Inc.
(Wicks) 4-drum water cube type with a rated steam load capacity of 125,000 pounds
per hour. Tie 1 1/4" to 10—nesh coal is fed via a Detroit Stoker toco-grate
spreader. The bailer is equipped with Zura aulticlone separators for particulate
emission control.
After a detailed evaluation of the existing boiler coal feed and overfire
air systea, it was determined that it was desirous to fire the RDF as close to
the traveling grate as possible. The selected system will fire the RDF immedi-
ately above the coal feeders. The RDF is to be air swept into the bailer by
utilizing part of the overfire air. To insure an even distribution of the RDF
across the boiler width all six existing coal feeder locations will be utilized.
The existing coal feeders will be repLacsd with a combination coal-SDF feeder
assembly. The combination feeders are of a standard design used to fire coal in
combination with wood chips or 'nog fuel.
To insure adequate overfire air for RDF firing and combustion, the existing
overfire air system was replaced to provide an increased capacity in overfire
air volume. The induced draft fans have adequate excess capacity for the addi-
tional air volume.
RDF Feed Svsrem
The RDF feed system was developed to provide flexibility in feeding the
RDF at varying feed rates to aeet the research objectives and to provide a very
89
-------
BOILER NO. 5
Ml—l : ELEV. 137'3"
vO
o
R.D. F FEED CHUTE (6)
FLOOR ELEV. 112'0"
EXISTING POWER GENERATION PLANT
BUILDING SIZE 40' X 70*
PLAN VIEW
OSCAR MAYER a CO.
R. D. F. FEED SYSTEM
EPA GRANT NO R8O632B-OI-0
RUBBER BELT CONVEYOR
EL. 103'3"
n
¦ n n I .
AUGER
DISCHARGE
SYSTEM
R. D. I".
RECEIVING
BIN
R.D. F. RECEIVING
a FEED FACILITY
BUILDING SIZE 36' X 48*
-1
FLOOR ELEV. 105* 3"
DIVISION OF ENGINEERING - CITY OF MADISON, WISCONSIN
.DRAWN BY T.L.J. 1-30-80
-------
OSCAR MAYER a CO. BOILER NO. 5
BOILER FEED
EPA GRANT NO. R60632a-0I-O
COAL
BUNKER
BOILER NO. 5
_ SLIDER -
BELT
CONVEYOR
BOILER
NO. 5
-R. D.F. -
FEED
CHUTES
COMBINATION
FEEOER
(6)
COAL-
CIIUTE
~ AIR —
INTAKE
]LJ[
GRATE
FRONT VIEW SIDE VIEW
DIVISION OF ENGINEERING - CITY OF MADISON, WISCONSIN
DRAWN BY 1 L.J. I-10-80
-------
clean system compatible with Oscar Mayer's high standards for plant cleanli-
ness for food processing. To maintain that standard, all RDF handling activities
will be housed in a building and all conveyors will be totally enclosed and
tightly sealed.
The delivered RDF will be discharged from the delivery vehicle (75 C.Y.
transfer trailers) onto a concrete floor. A small loader will load the RDF into
a surge bin. The RDF will be discharged from the bin by two fourteen (14") inch
diameter augers. The discharge augers are powered by a variable speed drive to
provide the variable RDF feed rates (1.5 to 10 tons per hour). The augers will
discharge the RDF onto a totally enclosed rubber slider belt conveyor to trans-
port the RDF to the boiler front. The RDF will then be split to feed the six
(6) combination feeders by use of a splitting roller and swinging chutes to
provide the desired feed into the boiler.
Test Program
The RDF-coal firing test program will consist of firing RDF at various
energy replacement rates and at varying boiler steam loads. Tests to be conduc-
ted will include (see Table 1):
1. Characterization of all fuels used in the combustion tests.
2. Stack emission tests while firing RDF and coal at the various feed
rates and boiler loads.
3. Boiler efficiency at the various RDF feed rates and boiler loads.
4. Operate the boilers for a sustained period at the optimum coal/RDF
mix.
RDF Quality
The RDF to be fired in the Oscar Mayer & Company boiler will be essentially
the same as presently fired at the Madison Gas & Electric power plant. That
RDF has a typical ash content of 10 to 127„ and a moisture content of 20 to 30%
as received.
Project Schedule
As of February 1, 1980, all RDF feed equipment and boiler equipment have
been ordered. Construction of all facilities is scheduled for completion by
June 1, 1980. It is anticipated that all test runs will be conducted during the
summer and early fall 1980.
92
-------
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I Sk.ilj sale HIiiui nl Slc-*e t'uaiun La I k - l^illiMe Flue Enlii- C(ll* M.m tUktt
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1'repareii by: The University of W1 flcona lu-Ma
-------
TEST FIRING REFUSE DERIVED FUEL
IN AN INDUSTRIAL BOILER
EPA GRANT NO. R806-328-010
GARY L. BOLEY, P.E.
PROJECT MANAGER
CITY OF MADISON, WISCONSIN
In 1979 Che City of Madison and che investor owned utility, Madison Gas
& Electric Company, jointly implemented a prepared refuse derived fuel (RDF)
energy recovery project. The City of Madison owns and operates a solid waste
processing plant to process municipal solid wastes for the production of the
RDF. The Madison Gas & Electric Company utilizes Che RDF in two Babcock and
Wilcox 50 megawatt pulverized coal boilers.
In the fall of 1978 the City of Madison in cooperation with Oscar Mayer
& Company were recipients of an Environmental Protection Agency Research Grant
to test fire RDF in an industrial boiler. The Oscar Mayer & Company could
represent a second market to the City for the use of RDF.
The industrial sector is a potentially large user of prepared solid wastes
as a supplemental fuel source. Industrial boiler installations are not able to
take advantage of the highly favorable fuel price advantages that utilities can
obtain, due to their high volume consumption. Therefore, industrial users may
be willing to pay a higher price per unit of energy for RDF than utilities.
Research Purpose
The purpose of the research is to investigate the feasibility of cofiring
municipal solid waste with fossil fuels to determine:
1. Industrial boiler operational performance when cofiring coal and RDF
at various boiler loads and feed rates to determine optimum operating
conditions.
2. Air emissions and performance of existing mechanical air cleaning
system when cofiring coal and RDF.
3. Operational characteristics of the RDF feed system and the reliability
and practicality of receiving, storing and firing RDF at an industrial
operation.
4. Economic analysis of utilizing RDF at an industrial operation.
Project Participants
City of Madison
The City's grant responsibilities, in addition to providing the RDF, include
overall project management, detail design of the RDF receiving facilities and
overall project coordination.
94
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Oscar Mayer & Company
Oscar Mayer & Company operates a meat packing plane in Madison. As pare
of their plane operations, Oscar Mayer operates a power plane for the cogenera-
tion of process scaam and electricity. One of ewo Wicks 125,000 pound per hour
boilers will be retrofitted for RDF firing. In addition to providing the
boilers, Oscar Mayer will also operate the RDF receiving and firing facilities.
M. L. Smith Environmental
M. L. Smith Environmental was retained by the City to provide special con-
sultant services to provide technical direction and staff assistance in the
Engineering evaluation of 3oilsr 'Mo. 5 to determine the method of RDF firing,
assistance in the preparation of the necessary documents for the boiler retrofit
work, develop the RDF receiving and feed process concept and system layout,
provide assistance in the test program development, and assist in the prepara-
tion of the project's final report.
University of Wisconsin-Madison
The University of Wisconsin-Madison, contracted by the City, will provide
the facilities and personnel necessary for all sampling, data collection,
analysis, and prepare all technical evaluations and reports.
Existing Boiler Conditions ana Modifications
Oscar Mayer & Company's 3oiler No. 5 i3 a Combustion Engineering, Inc.
(Wicks) 4-drum water tube type with a rated steam load capacity of 125,000 pounds
per hour. The 1 1/4" to 10-mesh coal is fed via a Decroic Stoker roto-grate
spreader. The boiler is equipped with Zurn multiclone separators for particulate
emission control.
After a detailed evaluation of the existing boiler coal feed and overfire
air system, it was determined that it was desirous to fire the RDF as close to
ehe traveling grate as possible. The selected system will fire the RDF immedi-
ately above ehe coal feeders. The RDF is to be air swept into the boiler by
utilizing part of the overfire air. To insure an even distribution of the RDF
across the boiler width all six existing coal feeder locations will be utilized.
The existing coal feeders will be replaced with a combination coal-RDF feeder
assembly. The combination feeders are of a standard design used to fire coal in
combination with wood chips or hog fuel.
To insure adequate overfire air for RDF firing and combustion, the existing
overfire air system was replaced to provide an increased capacity in overfire
air volume. The induced draft fans have adequate excess capacity for the addi-
tional air volume.
RDF 7eed System
The RDF feed system was developed to provide flexibility in feeding the
RDF at varying feed rates to meet the research objectives and to provide a very
95
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BOILER NO. 5
ELEV. 137 3
R.D.F FEED CHUTE (6)
vO
ON
FLOOR ELEV. 112 O
EXISTING POWER GENERATION PLANT
BUILDING SIZE 40' X 70'
13™—
PLAN VIEW
OSCAR MAYER a CO.
R. D. F. FEED SYSTEM
EPA GR/NT NO. R806328-0I-0
RUBBER BELT CONVEYOR
96 IO BETWEEN BUILDINGS-
AUGER
DISCHARGE
SYSTEM
R. D. F.
RECEIVING
BIN
R.D.F. RECEIVING
8 FEED FACILITY
BUILDING SIZE 36* X 48'
FLOOR ELEV. 105" 3'
DIVISION OF ENGINEERING-CITY OF MADISON, WISCONSIN
DRAWN BY T L.J. 1-30-00
-------
OSCAR MAYER a CO. BOILER NO. 5
BOILER FEED
EPA GRANT NO. RQ0632a-0|-0
COAL
BUNKER
BOILER NO. 5
^ SLIDER -
BELT
CONVEYOR
BOILER
NO. i>
-R. D.F -
FEED
CHUTES
Qi
\n
COMBINATION
FEEDER
COAL-
CHUTE
" AIR —
INTAKE
LZJt 1( ILL)
GHATE
FRONT VIEW SIDE VIEW
OIVISION OF ENGINEERING - CITY OF MADISON, WISCONSIN
DRAWN BY T.L.J. 1-30 80
-------
clean system compatible with Oscar Mayer's high standards for plant cleanli-
ness for food processing. To maintain that standard, all RDF handling activities
will be housed in a building and all conveyors will be totally enclosed and
tightly sealed.
The delivered RDF will be discharged from the delivery vehicle (75 C.Y.
transfer trailers) onto a concrete floor. A small loader will load the RDF into
a surge bin. The RDF will be discharged from the bin by two fourteen (14") inch
diameter augers. The discharge augers are powered by a variable speed drive to
provide the variable RDF feed rates (1.5 to 10 tons per hour). The augers will
discharge the RDF onto a totally enclosed rubber slider belt conveyor to trans-
port the RDF to the boiler front. The RDF will then be split to feed the six
(6) combination feeders by use of a splitting roller and swinging chutes to
provide the desired feed into the boiler.
Test Program
The RDF-coal firing test program will consist of firing RDF at various
energy replacement rates and at varying boiler steam loads. Tests to be conduc-
ted will include (see Table 1):
1. Characterization of all fuels used in the combustion tests.
2. Stack emission tests while firing RDF and coal at the various feed
rates and boiler loads.
3. Boiler efficiency at the various RDF feed rates and boiler loads.
4. Operate the boilers for a sustained period at the optimum coal/RDF
mix.
RDF Quality
The RDF to be fired in the Oscar Mayer & Company boiler will be essentially
the same as presently fired at the Madison Gas & Electric power plant. That
RDF has a typical ash content of 10 to 127. and a moisture content of 20 to 307o
as received.
Project Schedule
As of February 1, 1980, all RDF feed equipment and boiler equipment have
been ordered. Construction of all facilities is scheduled for completion by
June 1, 1980. It is anticipated that all test runs will be conducted during the
summer and early fall 1980.
98
-------
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-------
CO-FIRING REFUSE DERIVED FUEL (DROSS)
IN A STOKERED 30ILER
BY
FRED R. REHM, P.E.*
BACKGROUND
Milwaukee County operates a co-generation power plant facility at its 900 acre
Milwaukee County Institutions complex that encompasses a growing Regional Medical
Center. This power plant is equipped with three (3)-110,000 #/Hour coal-fired
Union Iron Works boilers and a single-125,000 fjfaour combination gas-oil fired
Combustion Engineering boiler. The coal-fired boilers are each fired by a Hoffman
"Firite" spreader stoker with a continuous front end ash discharge grate system.
The coal-fired boilers were placed in operation in 1954 and each originally in-
corporated an economizer, an air preheater and a Western Precipitation "multiclone"
mechanical centrifugal dust collector. In 1979, three new UOP-Air Correction
Division electrostatic precipitators were installed and placed into operation at
this power plant -- one precipitator on each coal-fired boiler. This plant cus-
tomarily bums an Eastern (Kentucky) coal of less than 2% sulfur content but has
operated for extended periods of time burning a Western (Montana) coal with a
sulfur content of less than 17..
With the startup of the American Can Company's "Americology" refuse processing
plant, limited test trials were conducted at this plant while firing both the RDF
"lights" and "heavies" (dross) fractions in conjunction with coal in the spring
of 1977. This RDF firing was conducted using a temporary pneumatic firing system that
utilized a farm silage blower setup similar in many respects to the improved pneumatic
firing system that had been utilized in an EPA R&D project at the City of Columbus,
Ohio municipal power plant. These preliminary firing tests showed sufficient promise
that an EPA R&D grant for more extensive and definitive evaluation of co-firing
of the dross or RDF "heavies" fraction along with coal was sought and received
in late 1978. Dross, or the "heavies" fraction, is the material left after
mrnicipal solid waste :'.s processed to produ::r a refined RDF "lights" fracticn
suitable for utility firing, a ferrous fraction, an aluminum fraction, and a glass
fraction. The remaining material (dross) was demonstrated to have a high com-
bustible content, but because of its unsuitability for firing in a suspension-fired
utility boiler, it is normally destined for sanitary landfill. The Americology RDF
"lights" fraction has been burned in the Wisconsin Electric Power Company's Oak
Creed Station #7 and #8 Boilers for two years now. Those that have attempted to
burn RDF in suspension in utility boilers have found that it must be substantially
free of metals, glass and other abrasive materials in order to avoid excessive wear
and pluggage problems in the pneumatic transport lines and to minimize slagging and
other problems associated with boiler operation. Utilities have also learned that
the denser combustible material in RDF tends to fall through the furnace without
burning completely. Unless a grate is furnished in the utility furnace to retain
this material in the high temperature zone, the heating value of the denser material
is lost. Generally, speaking, the steps that have been taken to improve the quality
of RDF "light" fractions for suspension firing tend to increase the quantity of
dross or "heavies" that must be disposed in a landfill. The denseness of this dross,
* Director of Environmental Services, Milwaukee County, Wis.
Presented at U.S. EPA-IERL "Waste-To-Energy Technology Update 1980",
April 15-16, 1980, Cincinnati, Ohio
100
-------
which makes it unsuitable for suspension firing in a utlity boiler, enhances its
value as a fuel for a traveling-grate, spreader-stoker firsd furnace. Thus, the
dense material tends to fall on the grate to effect complete combustion rather
than float up and out of the furnace as additional particulate. Our grata speeds
are relatively slow and hence furnace retention time in our boilers ac rated
capacity operation is approximately 80 minutes. Consequently, the successful
firing of the RDF "heavies" fraction in our spreader-stoker fired boilers is viewed
as supplemental or complementary to the burning of the RDF "lights" fraction at
the Wisconsin Electric Power Company pulverized coal-fired boilers.
PROJECT OVERVIEW
The RDF "heavies" for our project are to be supplied by the Americology plant.
Approximately 3000 tons are expected to be utilized in the 3 month test and evalua-
tion period. The following quality criteria have been established for the "heavies"
fraction.
Less than 127. glass by weight
Lass than 37. metals by weight
Less than 257. total noncombustibles by weight
Less than 337, moisture by weight
A nominal top size of less than 4 inches
Average heating value range 4000-4300 3tu's/#
The RDF "heavies" are to be transported to the plant by use of Waste Management,
Inc. 15-ton self-unloading trailers. For the purposes of this project, on-site
storage to provide for an uninterrupted supply of the RDF will be effected by use of
Waste—Management trailers. The County's power plant is approximately 6 miles and
10 minutes away by direct freeway travel from the Americology plant.
The RDF fraction will be received in a screw conveyor bottom receiving bin
capable :of receiving a substantial portion of a full trailer load of RDF. The
trailer will be positioned to continue to feed the receiving bin as the RDF is
burned. We anticipate an RDF feed rate ranging up to 5.5 tons per hour for these
tests. Fcr •purposes of these tests this arrangement will forestall the need for
supplying a large RDF receiving and storage facility. The rate of operation of the
screw conveyors in the receiving bin will be the mechanism for control of the RDF
feed rate to the test boiler. One of the three exising boilers will be used in the
project. The controlled RDF feed material will be fed to a pneumatic airlock feeder
and will be transported pneumatically to the front of the test boiler. A single
pneumatic injection RDF flared feed spout will be located in the front wall of the
boiler approximately 10 feet above the top of the^travelling grate. This location
is approximately 7% feet above the centerline of/^oal-feeder reel which projects
coal into the furnace. An extensive evaluation has been made by our consulting
engineers on this project, Charles R. Valzy Associates, Inc., of the possible use
of a mechanical RDF transport system at our plant in lieu of the pneumatic system.
All parties involved in the project would have favored the use of a mechanical RDF
conveying system to avoid' some of the demonstrated problems found by others that
have been associated with pneumatic RDF transport. Unfortunately, physical space
limitations within the power plant make the use of a mechanical RDF conveying system
impractical.
101
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The first two months of plant operation will be used to establish the optimum
RDF-coal combination firing rates at various boiler load rates of operation. During
this trial period, consideration will be given to the following parameters in
establishing and evaluating the optimum RDF substitution rates:
RDF receiving, transport and firing system problems and limitations
Impact on the steam generating capacity of the boiler
Stability of steam generation
Excess air requirements
Boiler thermal efficiency impacts
Carry-over of fuel into the boiler convection bank and boiler slagging
Grate residue and fly ash production
Residue combustible loss
Adequacy or limitations of our pneumatic boiler ash conveying and ash
storage facilities
We expect to explore RDF substitution rates ranging from 20% to 50% of the
total boiler heat input at boiler steaming rates ranging from 60% to 100% of
rated boiler capacity.
Once the two month trial period is completed, we plan to operate the test
boiler continuously for approximately thirty (30) days at the optimum RDF input
rate established in the trial period at or near 80% of the boilers rated steaming
capacity -- the normal rate of boiler operation at this power plant. During this
30-day test period, we expect to conduct a comprehensive system and environmental
performance analysis. The boiler and its related firing and ash handling systems
will be evaluated and assessed for the aforesaid operating parameters previously
outlined. RDF and coal analyses will be regularly conducted for heat content,
moisture, ash, chloride and sulfur contents. A limited number of analyses of the
RDF and coal will be conducted for their heavy metals content. Concurrent electro-
static precipitator inlet and outlet particulate testing will be performed both
while burning coal alone and at the optimum RDF coal substitution rate. The sampled
particulates will be analyzed for resistivity, combustible content and particle
sizing. Gaseous emissions will be assessed for criteria pollutant loadings as well
as for hydrogen chloride. Gas volume and temperature measurements will be made and
Orsat analyses will be conducted. The grate ash residue will be quantified and will
be analyzed for Btu content, combustible content, putrescibles and leachate potential.
Much of the environmental sampling and analytical work for this project was to have
been done by EPA contractors which were funded outside the grant project. Conse-
quently, we will have to carefully prioritize the sampling and analytical program
conducted to stay within our project's budgetary limitations should EPA funding for
this aspect of this project be restricted, as now appears to be the present situation.
Our present timetable calls for our field testing program to be conducted in
the Fall of 1980. We are restricted to the conduct of the field portions of this
study to either the Fall or Spring of the year since the stean & electrical load
demands in this power plant for our Medical Center would preclude the availability
of the test boiler for this project during the heavy winter heating load and summer
air conditioning load periods. The field test portion of this project was originally
scheduled for the Fall of 1979. However, due to an explosion at the Americology
plant and subsequent changes and modifications made at that plant, it was necessary
to delay this R&D project by one year.
102
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PROJECT STATUS
We have conducCed numerous operational tests at the Americology plant in the
past few months directed toward upgrading the quality of the RDF "heavies" fraction.
This has involved some plant revisions in the plant's RDF "heavies" processing
operations. While the RDF "lights" fraction processing lines have now been modified
and adjusted to produce a high quality RDF "lights" fraction for firing by Wisconsin
Electric Power Company, there have been limited permanent revisions made to the RDF
"heavies" processing system to date. Consequently, there has been need to make
temporary changes in the mode of plant operations and in the upgrading of the netals
and glass removal operations to improve the quality of the RDF "heavies" fraction
to facilitate and enhance its handling and firing capabilities. Should the R&D test
program ultimately prove successful and markets for the RDF "heavies" fraction become
available, the Americology people would then consider incorporating the aforesaid
temporary system changes into permanent modifications to their system that would
provide a RDF "heavies" fraction of equal or superior qualities than those used in
this research project. The analyses of the RDF "heavies" fraction from one of the
series of recent operational tests is shown in the accompanying chart. It is felt
by the Americology people that the quality of this material can be further improved
by fine tuning the various operating systems in the plant during periods of more ex-
tensive running time than those provided in the ^ hour or 1 hour test periods that
were used in the operational test runs to date ana which would be required during
the actual R&D project burning period. Additional operational test run3 will be
conducted under varying operating conditions at the Americology plant in the coming
months to further reduce the quantity ox material greater than 4" and to reduce the
amount of glass and other incombustibles in the RDF "heavies" fraction.
Preliminary evaluations and designs for the RDF handling and firing syscem
at the power plant are nearing completion and are expected to be completed soon
and the installation of the RDF handling and firing system is expected to be bid
in the near future.
Precipitator particulate emission tests have been conducted on all three coal
fired boilers while operating at rated capacity while burning Eastern coal. These
emission tests were conducted as part of the performance- acceptance tests for the
new electrostatic precipitators. These test results will be utilised in establishing
the baseline for comparing the emission results of coal only burning versus co-firin"
of coal and the RDF fraction. A table showing the preliminary results of the partic
late emission tests for the ?;3 boiler is attached.
103
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HEAVY FRACTION FUEL ANALYSIS
TEST ON 1/24/80
NON-FERROUS &
MOISTURE = 26.7%-
BONE AND
FLOATABLE ASH =
FUEL
GLASS
14.6%
TAILS =2.7%
NOTE: PERCENTAGES SHOWN
AS RECEIVED BASIS.
PARTICLE SIZE (AVERAGE OF 3 SEPARATE SCREENINGS)
4"
78%
2"
71%
14"
65%
1"
56%
3/4"
45%
V
31%
104
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Table 1. Summary o' the Results of the May 30, 1979 ESP Performance and Particulate Emission Test on the No. 3
[toller ESP firod with Eastern Coal at the Milwaukee County Institutions Central Power Plant In Milwaukee, Wisconsin.
1 Tf.M
RUN
\
RUN 2
RUN 3
INLET
1 OUTLET
INLET
OUTLET
INLET
OUTLET
Tlmo ol Test
(MRS)
1020-1130
1015-1130
1220-1350
1230-1347
1418-1535
1415-1530
Stearn f1ow
(lO'LU/IIR)
109. 1
109. 1
1 10.9
110.9
109.8
109.8
Pcrconl of ratec
capacity
99.2
99.2
100.0
too.a
99.8
99.8
Vo 1 unto 1 r I c Mo*
ACTUAL
(ACFM)
66600
63200
67100
66200
66700
64600
STANDARD
(DSCFM)
39400
37900
30700
39000
38800
38400
Gas Temperature
(DCG-F)
356
344
363
345
362
345
Gas moisture
i% v/v)
6.43
6.24
7.99
7.78
7.42
7.08
Gas composition
(% v/v, dry)
carbon dioxide
11.13
10.94
11.31
10.97
11.18
11.17
oxygen
0.32
0.63
8. 14
8.65
8.27
8.35
n 1 1rogun
00.55
00.43
00.55
00.38
80.55
00.48
TIme-averayed velocity weighted
oxygen
(% v/v, dry)
7. 74
8.66
7.76
8.43
7.97
8.42
Particulate concent rat i on
ACTUAL
(GR/ACF)
. 11
.024
. 1 1
.021
. 1 1
.024
STANDARD
(GR/DSCF)
. ID
.040
.19
.035
. 19
.040
Isokinetic variation 1%)
99.7
90.3
103.9
101.7
103.0
100. 1
PartIculale mass
rate (LO/llR)
59.7
13.0
65. 1
11.7
63.0
13.0
ESP co 11ec ti on ft
t 1 1 ciency (jC w/w
70.2
02.0
70.4
Pressure drop across ESP (in. wc
.53
.53
.53
Particulate emission factors
(Ln/I06I3TU)
Co.i 1 'low me 1 hod
.45
.099
.50
.089
. 48
. 102
Steam flow method
.46
. 101
.50
.009
.40
. 100
F-Fuclor method (02 Analyze
) .39
.097
.43
.082
.42
.093
F-l ticlor method (orsal)
.41
.096
.44
.083
. 43
. 092
-------
CORROSION INHIBITION IN REFUSE-TO-ENERGY SYSTEMS
H. H. Electric ?lant. The Sanitation
Dlvisipn transfer trucks had tp oe emptied in 20 to 30 minutes during
the daytin* to avoia relaying snredaer ooeration. Put could be used for
storage and/or retained for longer periods at nignt.
Assuming an average steam flow of 100,00 (b/hr (45 Mg/hr) and
:0 sercent of tne neat generatea by refuse, tne amount used per nour
would be about seven to eight tons (6 to 7 Mg). Thus, a truck load of
refuse could be delivered to the power plant every two to three nours during
the day and also through the night by storing refuse in the trucks from
the daytime operation of the snredders. After consideration of the
available space and possible equipment arrangement at tne power plant,
it was decided that the most suitable and cost-effective storage unit
-ould consist of a bin similar to tne transfer truck body with a nyorau-
11c ram to feed the refuse as required.
The remainder of the external system comorised: (1) Peater
bars at the end of the bin to break uo the refuse, (2) screw conveyors,
(3) a 30 in. rubber belt conveyor, and {*) an inverted i hooper to receive
the refuse from the cpnveyor pelt and direct it into two screw conveyors.
The refuse storage and retrieval system is shown in Figure I.
The refuse stream was divided at the Y hoooer so tnat the
larger portion was fed to the front of the boiler, near tne soreaders.
The two screw conveyors inside the building delivered tne refuse to Riley
air-swept soouts wnicn were inserted in the side of tne boiler, at a 90
degree angle to tne grate. The modification of tne boiler tubes to
acconmodate the spouts is shown in Figure 2. Wnen tnis boiler was con-
verted to a spreader stoker some years ago. the direction of tne grate
travel was not cnanged, so tne grate movec away from the spreaders. For
this reason about two-thirds of tne refuse -as introduced througn tne
soout on the rignt. just in front of tne soreaders. The boiler modifi-
cation also Included installation of overfire air jets beneath tne refuse
spouts and across the back of the furnace. Ouring corrosion prooe expo-
sures tne refuse feec rate was three to five tons/hr.
Refuse Comoustion
The boiler used in this program is rated at ISO.000 lb (68 Mg)
pf steam per nour, but normally was operated over the range of 70,000 to
125,000 lb (32 to 57 Mg). In order to insure good distribution of refuse
across tne furnace, a rotating damper in tne duct of eacn air-sweet spout
produced pulses to vary the input. The fuel trajectory was concrolfed oy
angling tne distributor plate either
-------
Corrosion faults
Corrosion rates «trt oy -«iqnt lots .nttsurw*nca
jfter rwvil of me react** matal Jiinq innioited 10 oercent H3SO4 -nile
me sarnie «4s Mde tu vales :atnodlcto 4 caroon 4nooe. The corrosion
rate in nils Otr tour «4S calculated from me *tignt loss, 4ssur8inq
jntfom attaci iround ye lStcimm surface. fhe corrosion fjtts m me
coflring nvironrr^t for Aiaa ciroon steel is 4 function of :1m ire
tnown «n .'Igure 3. The corresoonaing rues for !00 oercent refuse to®*
Sustion *tre ootatnm from Mt orevtous txooiures ;o .^ass ourning of
refust 4c me .Hani County incinerator imj jrc snow* In figure *. • itn
niqn* sulfur coal ino uo to *6 -tignt-otroent 'tins*. me initial racts
«trt 'ttiuceti oy 4 factor of ten. As m* exoosure time increastd, mt
rates for 100 Jtrcent refuse ind ccal olus refuse oeca» cldstr. out mt
s/14041 of mt cjr»ts inatcati mat 'or utended ooosurrs in conrojivity
of mt 100 oeroent refuse canoustion environment ^ 111 ot ioout 5 to 10
;tni m4t of lit mgn«iulfur tMl «tut refuse.
in gtntral, mt rotes .'or m« refuS«*C04l .nliturts »er« aoout
mt same is for mt coals 4lone. '41 w caroan steel im 3 otrewt sulfur
C04l, jjrmion rates sMgntly greater ic 700 4rtd 400*? (371 ind
462*C). ?or me S stretnt ml fur cul mt relatively sign rates **r* mt
result of sulfur attaci on mt stfrti. JU of mt corrosion rates nMiurM
4c me Coluwxis site <«n* saaller man most found .'or sulk refust Ournmq
3y 4C Itest 1 .'actar of tM, 4n4 In $ooi cases, oy 1 'ictar of Mfty.
Di« fnlti4l carrwicfl r*cas (3-ftour) for AlOfi su«i a a .'ynctlon
of 1*9 rtfm« 3«rcaflU9« In Lit .'y«l 41-t oresencta In flgurt 5. riMS
««r« euer»ci*!1y inseo«ttd«nc 3/ :.i« 4flounc of ^?fus« In nixCurt, 40
ia 1*9 1% •ciqAt-oireent 'jirt. D>« 1Q0 a«rc«nt <«lues in :n« Mqurt «r«
yie ouli refuse iflcm®rjt1on eaO«r1a*«nes. 4nd U i 1 outet 9oss1bl«
Vt«C ^ts« v«lu«i «ou)d a« a>0««r if mr»cfl*G r«fus« ««rt lurnM unatr tanr-
Mrtoit drcienuftces.
•fttn tflt eioosurt :iam *41 ieriqtntflefl to 30 noun, zm cornj^ion
rjtss for ill of :ne j:«Is ««r* r«ucw 4s 4 r«sule of :ne :rocac:iv«
oiiot l4y«n «ntci 3#v«loow3 on 1*9 ncil surficsi. 4$ found in :n« «ione
.vjur tMOomrti, :.** '/Q9 JIO uainltss kmI n4d cn« lowvit comsion net.
follow 5y tn» T*99i J16 100 tcamless tcnii. rh« '9 411 oy -na 4
11»cjjicly Aigftvr *4t«, 4«» :n* iCJCtir in tn« 341« for cn« P9 totciowil 11
4Ctri0u(«d to tfM®ty:y of \*i\ lUoy to 'jnnryj tulIUq if *.n« zxi49
flln. fMi iffKt «ouid result in sen* ineaniMetncies of ««iqnc loss
imnq vtt swles. il:nou<5n l*t« corrosion rits for A106 caroon icmI *4k
uqniflcandy lo*«r v.tr :rwc 'or #iqnt .*reur noosur«j. it »4S mil ioout 4
factor of :tn ^nattr man *jiat for \r,9 uamltss s:t«is.
Hit inttrrolatta <4iuts for ir,9 lonq^ctm corrosion rsa?s *rt
^v«ti in r^olt I, -aten inciudts data fzr 1*9 /C3 naur con-^jtgn arso* «*PO-
sur«. ^s tnoM in :n« uol«, corrosion ''acts <;tn«rally decreased fur*.i«r
«itA ct« lonqtr '.in. to -«trc v,f«y navt oroMoly l«wl«d off *ould
.tat S9Crsn9 s1<^itficantiy -its uiditional «iootun. Tyce 210 ttainl«is
fCMl, *^lcn ilr*4dy Ud 4 very low corrosion ratt for ;ne 79 iour timun,
incurred V9 14m rata H 500 4nd 700*5 in 708 nour tiooiure, -Ufi i
'itcrtast 4C TOO*?. At j .^tcil t«oer3Curi jf 50Q*P :.ld *106 cnl ilio
.ltd Vt9 lant rsct for *jt« r*o excosurv ttsvs. (t snouio :• nottd Lite
-«#n on# itrcmc ml fur cotl «4s oum«d «icn only 1$ -^Kjnt-ctrcwt r?fyst
{Proot -uJ), tne comsicn r»ct of -*106 ixtdl -as Mgn«r. r?itt r«sult
inqicatas «"uc wH Ic»-43 >0 critical :otlir^, 44C.1 «itf 4 mammal ciMd'.y of 340
r/day (127 :ay) of refust. it yij ritt of IS tans (13.5 if
••fusa :«r iour, :.i« nonnal :racuction ii 32.500 io/!ir J42.3 ^/fr).
Hit Ct4fl orestun u :nt fuotmtaeer outlet m ^SO ssig J"!3.5 '*gj ;er :4y of zry solios. ^ur^ng ;.-e course of vitst
:orros«on studies, we :ar*i|l!/ jHec sludge *4S velivtr^d Jt jn 4*«rsgt
-ate of lfi.S tons MS ^g) atr zoning siy. Ourmg t.ie 3-^our jnd 20-"Our
3root eioosures. tne «eignc ratio of sluage to solid -astt >as icout i:10
on dn 4$-r«cti*efl iasis. Out tyring :.it long-:jrn rjn t.ie ritio oroooed to
lOQut 1: -*C
is t'jrrenfjy ;rict:ctd. *."« te^terw sluage 'ilttr :»«e :on-
utninq ioout U otrcsnt solios 'S aiieo *1 t.i tne ¦numeral refuse in t.ie
.-ecsfing 31;. lanndtraoie ^uing occurs in tne oit tefort t.ie sludqt
tnc "t'usc ir? 'ti fnto t.ie '-jr-ace :.*.ar5:nq c.iute. it seefneo likely t.na;
suifur inc iiHci ««rs jrese^t in tae ^luagt in sufficient ;uanoty ina
•er* :urneo est results ire tonoarrd -«w t.ie
:orrosion data ootained oreviously it tfle .Hani County inc'fleritor it
"roy, Ohio, «ntre oul'i refust alone «ts :umed. Hit data *«re interpolated
fro® several lotcimtn ternotracures to 1 cofltnon temotracure of iCO*^ '.250*t).
rhis teootraturt 9 corrosion rate «as sligntly niqntr it Troy otcaust vtt
3root tntre *as excostd 10 some flart natation.
addition of sewtgt sludgt to wit refust reduced t.ie initial
corrosion r»t* of W caroon r.Mt 5y soout 1 fsctor of t>o. itr««ver. is
tst ?*oosure tin* tncreastd. tnt corrosion rites for octrstion w»t.i jnd
• unout sludge convergeo. Thus it tat 300 wur ooint. t.it rite «>oerienc»d
for tnt s.'aall muntl of sludgt 3urned 4t Harrisourg *ts only sligntly less
man mat for refuse alone it tnt 7roy [ncinerator. levertreless. if t.it
4lfffrmc8 In tnt t>d cjrvts at me 1000 ie *?2 alloy nad ^tal
•4stage rates essentially t.it saint is most for t.ie tarocn steel. Sig-
nificantly lototr rites *tr« oostrved for me Tyoe JIC ind J*7 stainless
Jtttls ind tnt incoldy 32S.
tffect of «etal 'effotrsture
A slot of «4SCagt rites for -i 106 carocn ttatl over me te^otrature
rimjt jOO to 300*F for me ngnt nours «*oosure to t.ie Oum«ng refuse -itn
ind -1 tftouc sludge loouion^ is irra^n in figure 7. "nt line ora««i on :iu
figure frca me studies conducted 4t tae Troy, Ohio, incinerator Is oaseo
uoon ten or rore A1C6 soeciotns ixoosed it 1 ;as terotrsture of 'WO*?
(316*C) «nicn is cs««raoit to met :f me Marruaunj srooe in me suoer*
ieater inlet, rht increase in corrosion *ste starting it 300*? (*27'C) ts
tyoical of mat found for caroon s;iel ind lew alloy steels in our 34st
eiocnenci vim me 3uminq of ouU refuse 4t ncn ;as temtratures. The
mrev oaca ootnts ootaintd for me ciroon steel exoosto :o coffotraole ton-
Jiticns in me Harrisaurg Incinerator fall clost to tne curve tstaoMsned
for mt Troy incinerator, rhe corrosivity 3f me tnvirowwnt -41 signifi-
cantly reduces «n«n tnt sewage sluoce **i ourntd -it.i t.ie refuse, -s
snown in 'igure 7. mt eignt ."tour corrosion rates «im sluaqe ore^ent in
mt futl ire Z to 2.2 tines lower tntn taose «i m refuse ilone.
Similar conditions ind results ire s.iowi in "'.gyre 3 for me
low taromiua il»oy. 'ZZ no* ^etng -jstd for me suotrreatar tuces 'n me
harrisourg incineritor. r>ie olfferencs :n corrosivity of t.ie r*o fuels
aecooes i*re ;ronounceo -'or totn illayi is me T*tal tmoerature increases,
^rtre again me line sra»n in :,ie figure mi ootamed it *roy for i mnilar
low enroffliufl illoy. *11. (n cemoarmg tae Jtrfomance of ciroon steel ino
'21 -ntn sewagt sluage *as turned aim t.ie .-ef'j.«e. littla iifference -4j
soservtd in me ::rnsion rates, ss .iotsd in ;iguns 7 ind 3. «hen r-'use
ilone -as ourntd me corrosion rste for 722 liloy -4S sli;n?'/ '3-er man
tnat of i106 it terroerstures jo to -'CO*? [270"!). ^cwtver. it ioout 300*?
(¦*27*C) tnere «as little difference in tae corrosion -ice of tae t'*o
rsaterials. These results iroicace mtt t.ie reduction in :uce 'ulures 4t
tae H4rrisourg incinerator sn recent years -45 not mt result sf reolacmg
caroon steel tuots -'ta mt *22 illoy.
3om T/gt )10 ino 3*7 iutnless steel is tst tlg.i caroaiun-^ickel il'oys ifforted
rore orotectlon is me trroerature incroastd. ;rnoaoly :ue to ^or? *ioid
diffusion of tae mrsmium ina nickel into tae ou'de liyer -it.n t.:e 'oma*
tion of \ mic*er jrotective scale. *>:« iOdition of sludge to tae rer'-jst
•ao oracticjlly .10 affect 3n tie corrosion rues sf T/oe 3*0 ino 3^7 stain-
less scttl. T^e sludge 3td. io*«vtr. sMgntly r~juce tie ittac* on
[ncoloy 325. oarttcuiarly it >o«tr tesiotntures.
Iffect of las 7eraerU:jre
*or mis srograw '.••o oiffer-nt 'ocac:ons for ;rooe ncosure *er*
selected :n tne Jasis of meir 54s teiaoeritures. The ngner te^oerature
location «4S in 'ront :f me f*>st suoeroeater oan« ino j feet oelow tae
location 3f tne slant memocouole 'or fumace te^oeritur* ?ta»urefv»nt.
jas te«Oeracures in mis :one ire romtored ind itintamtd ".ear !:00*r
'31S'C ].
:>o of t.ie eignt idur ;rcot "ins -ere iace *n 1 relatively too!
location «nica «as icout ;5 ft :ow^strein> of tae rotter location. 5t mm
joint mt vjees •««•< 3racticaliy tUc* »no tie 54s teroenture is xn»t;reo
107
-------
by una orobe thermocouple was in the range HOO-12QO*F (593-650#C). The
corrosion raws of tne carpon steel and the P22 alloy exposed at low gas
temperature snowed only a slignt variation Kith metal temperature as com-
pared to Figures 7 and 8 where the corrosion rates Increased raoidly with
ratal teocerature wnen exposed to high gas tenoerature. The corrosion
data demonstrated that the same reduced temperature dependence existed at
low gas tempera tyre when the sludge was burned with tne refuse. Under
these low-temperature conditions, utere »as no apparent difference in we
corrosion rates between the caroon steel and the ?IZ alloy.
It srtould be noted that a reduction in gas temperature Is more
effective in reducing trie corrosivity of the environment over the entire
ratal temperature range tnan is the addition of sludge to the fuel. Thus
although additives to the refuse nay imgrove the life of boiler tubes the
design of the Poller to reduce the teaoerature in the steam generator
section would also provide a significant improvement In boiler tuoe life.
CONCLUSIONS
The experimental program conducted at the Columbus. Ohio
.Hunicipal Electric Plant has demonstrated the technical feasibility of
mechanical handling and furnace feeding of orocessed municipal solid
waste at an existing stoier-fired Doller with United space and acces-
sibility. It also has Seen shown chat the refuse comoustlbles can be
burned completely on a grate in conjunction with coal, utilizing a
spreader-stoker.
The following specific conclusions can be reached:
1. The corrosivity of combustion products from cofiring
refuse and three percent sulfur coal uo to a three to
one weignt ratio is only slightly greater than that
of coal alone.
2. Boiler tube metals can oe ranked in the following order
of increasing resistance to corrosion: A106 carbon steel,
?9 low alloy steel and Types 316. 347, and 310 stainless
steel.
J. The corrosion rates of boiler tube metals decrease
raoidly witn exposure time. After 700 nr the rates for
stainless steels level off.
Corrosion prooe exposures conducted at the Harrisourg, Pennsylvania,
incinerator demonstrated tftac tfie addition of low-cnloride sewage iluage to
municipal refuse reduced the corrosion of susceptible ratals caused by chlorine
in en* refuse. Soeciflc conclusions from this researcn prograoi were:
1. The corrosiveness of the refuse combustion environment
to carDon steel as indicated by 8-nour exposures was
only 1/2 as great with sewage sludge present. Less
reduction occurred at tow temperatures witn 722 steel,
very little witn Incoloy 325 and essentially none witn
Types 310 and 347 stainless steel.
2. For carton and low alloy steels the corrosion rates
increased with ftetal temperature in the range S00-300"F
(260~482°C),
-------
house i. nsniss stste! at coluxsus, ohio
municipal siicntic ?unt
3oii«f b«
modificstfort for
Qir-iw€?1 sooyts
t'gs?.z :ntsl?ac: tsansto rrs~
AMD 30ILZR :*.00EJICATICS
109
-------
Metal Temperorures
950F 510 C
750 *00
550 270
0.2 5
Hours
Metal Temperaiures
X
950 F
5I0C
~
750
400
<1
550
270
0
350
180
t 0.05
Hours
1000
CORftOSICN RATES OF A106 CAABO.M STEEL AS .
FUNCTION OF TtllE FOR COfniNC OF REFUSE
AMD HtCH-SULFUR COAL
COttOS tCW RATES OF A106 CARBON STEEL AS .
FUNCTION OF TC1S FOR INCINERATION OF
SULK RETJSE
0.20
= 0.15 -
OJ
o
o:
o 0.10 -
o
U
.9 0.05 |-
'c
Metal temperature
• 500 F ( 260C]
• 900F (482C)
I
I
I'l
Jh
/
/
4J
aj
2 £
2
0
1
I
0
0 25 50 75 100
Weight Percent Refuse (with 3% Scoal)
INITIAL CORROSION RATES (8 KR) FOR A106 CARBON STEEL
AS A FUNCTION OP REFUSE PERCENTAGE IN THE FUEL
(100 PERCENT VALUES FRCH BULK REFUSE INCINERATION)
110
-------
M«nn *«mo«rQTuff, C
*00
Tgo««
Q Staam 3to«n
I ^
3 -5
3 :
5 "
-------
C0-F1KJNG DENSIFIED REFUSE DKH1VED FUEL
IN A SPREADER STOKER FIRED BOILER
Gerald H. DegJer
Carlton C. Wiles
ABSTRACT
As a resource recovery a1tt-irnative, the use of refuse-derived fuel (dRDF)
is being investigated as a substitute for coal in industrial spreader
stoker boilers. Experiences are sumir.arized from the combustion testing of
1/2-inch-diruncter pellets using a modified animal pellet mill. Storage and
handling experiences are also discussed.
Approximately 1800 MG of dRDF have been burned in a spreader stoker equipped
boiler. The first phase of the combustion tests involved an evaluation of
boiler performance and emission when firing at coal:dRDF blends of 1:0,
1:1, 1:2, and 0:1. A total 245 Mg of 1/2-inch-diameter by 3/4-inch-long
pellets were consumed during these tests. The second phase of the combustion
tests involved the combustion of 1555 Mg of pellets. Results are presented
primarily from the Phase 1 test. Results from the Phase 2 test will be
available -in the near future.
INTRODUCTION
Densified refuse-derived fuel (dRDF) is considered one of the more marketable
products recovered from municipal solid waste. UTien densified in the form
of pellets, cubettes, or briquettes, it can be easily handled, transported,
and blended with coal and burned in existing stoker fired boilers without
major equipment modification.
As a result of previous encouraging coal:dRDF tests, the U.S. Environmental
Protection Agency sponsored a technical and environmental evaluation of co-
firing tests conducted at the Maryland Correctional Institute (MCI) power
plant in Hagerstown, Maryland, and at the General Electric Plant in Erie,
Pennsylvania. The dRDF used in these tests were pellets prepared by the
National Center for Resource Recovery (NCRR) and Teledyne under parallel
contracts. The following discussion presents the results from the Phase 1
test.
TEST OBJECTIVE
The objective of the study was to determine, characterize, and demonstrate
the technical, economic, and environmental feasibility of combusting dRDF
with coal in spreader stoker-fired boilers. The study was to specifically
address the fuel handling, boiler performance, and environmental effects
when dRDF pellets, cubettes, and briquettes were fired with coal in boilers
rated at 11,300 to 90,400 kg/hr.
SITE SELECTION
The Phase 1 testing was conducted at the State of Maryland Correctional
Institute for Men, located near Hagerstown, Maryland. The boiler plant
consists of a battery of three saturated steam 150-psig Erie City boilers.
The testing was carried out on two Erie City boilers rated at 27,200 and
35,600 kg/hr (60,000 and 78,500 lb/hr). The boilers were equipped with
Hoffman Combustion Engineering "under throw" spreader stokers, vibrating
grates with front ash discharge. The Erie City boilers are a tube-and-cile
construction co-posed of wide-spaced nominal 3 1/4-inch-diameter tubes that
were later partially embedded in refractory to approximatey 8 ft above the
grate. The gases are exhausted from the furnance through a two-drum boiler
112
-------
h.ink, consisting of rows of 2 1/4-i.nch-dinineter tubes, with two gns p.rscs.
The flue jasas are cleaned in a two-stage multiclone collector. The fly
ash gathered in the first-stage collector is reinjected into the boiler 10
complete combustion of che fly char, and the fly ash in the sr-cond-stage
collector is pneumatically transported to disposal. The cleaned easos are
induced through a centrifugal fan and exhausted to a common breaching and
stack.
TEST DESIGN
The test design called for the combustion of 253.5 Mg (235 tons) of d?JF
during 236 hours of firing various bland ratios of coal:dRDF. These tests
were conducted in a series of burns with volumetric coal:dRDF ratios of
1:1, 1:2, and 0:1 and with test durations ranging from 20 minutes to
132 hours. Each coal:dRDF test was preceded and followed by a coal-only
test with duplicate conditions. The field tests involved a comprehensive
study of (1) the material handling characteristics of dRDF, i.e., storage,
conveying, feeding ouc of bunkers, ecc. ; (2) boiler performance, i.e.,
grate speeds, underfire and overfire air requirements, steam production,
spreader limitations, boiler efficiency, flame impingtmpnc, slagging,
fouling, clinkering, combustion gas analysis, etc.; and (3) environmental
performance, i.e., particulates, gaseous emissions, and trace organic and
inorganic emissions.
Since only pellatized dRDF was available, testing with cubettes and briquettes
was not conducted. Also, because of insufficient plant stean demand, most
of the testing had co be conducted at 30 to 55 percent boiler loads.
TEST RESULTS
Material Handling. Throughout the 6 months of field testing, 258.5 Mg
285 tons) of dRDF were received, stored, and conveyed to the boiler without
major difficulty or malfunction. At successive periods, the pellets were
stored in tarpaulin-covered 20-yd3 drop boxes, in a warehouse, and on an
outdoor concrete slab.
Drop Boxes—Since the pellets were received in covered drop boxes during
the winter, they tended to steam and eventually freeze into a solid mass.
Minimal roading, however, broke the mass into blocks, and subsequent
handling further reduced che blocks to individual pellets.
'varenouse and Open Slab—Approximately 125 Mg (140 tons) of pellets were
stored in an un'neated warehouse for 2 months. With the exception of mild
offensive odors and some fungus growth, this storage proved co be the most
effective in maintaining pellec integrity over extended periods of storage
time. Since the depth of the piles was limited to 1.3 a (5 ft), increases
in tamperature due to composting effects were negligible, and the pile
stabilized at 60°C (1^0°F). The pellets stored in the warehouse were
subsequently moved to an outdoor storage area. The pellets were stored in
l.S-a (6-ft) piles on an outdoor slab and covered with a tarpaulin. Moisture
accumulation under the tarpaulin caused pellets at the top of the piles to
deteriorate and cake. Also, some pellets sustained minor damage, i.e.,
swelling and roughened edges, because of water infiltration due to poor
drainage.
Pellet Feeding—The pellets were conveyed to the boiler feed hopper by a
temporary fuel blending and handling system. The coal and dRDF were
volumetrically blended in the various ratios by separately feeding coal ana
pellets from two hoppers to a common bucket elevator which subsequently
conveyed both coal and pellets to a weigh lorry. The fuels were accurately
blended by filling che feed conveyors to capacity (level with the conveyor
113
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flights) and operating the feed conveyors at speeds coircmtnsurate with the
desired blend ratio. Although this feeding system generally worked well, it
had some difficulties with deteriorated pellets. As the amount of fines
increased, the pellets would not flow from the feed hoppers without redding.
These fines also caused considerable dusting throughout the p]ant. This
dusting was subsequently controlled by installing a stcjani jet at the con-
veyor transfer point.
Pellet Properties—The 1/2- x 3/4-inch pellets had an average bulk density
of 425 kg/m3 (26.5 lb/ft3) and ranged from 400 to 466 kg/m3 (25 no 29 lb/ft3).
The material density for intact pellets ranged from 1.22 to 1.34 g/cm3
while that for deteriorated pellets averaged 0.98 g/cm3. The as-reccived
properties were 12.10 to 15.12 MJ/kg (5200 to 6500 Btu/lb), 20 to 29 percent
ash, 9 to 10 percent fixed carbon, 12 to 13 percent moisture, 50 to 57 per-
cent volatiles, and 1142°C to 1152°C (2088° to 2105°F) hemispheric fusion
temperatures.
Boiler Performance. Feeder Performance—The 1/2- x 3/4-inch pellets
generally handled and fed well with the larger pellets traveling to the
rear of the grate and the fines falling close to the spreader. During the
initial combustion tests with 100 percent pellets, the spreader had to be
adjusted to decrease the pellet trajectory by approximately 0.3 m (12 in.).
In addition, due to volumetric feeding capacity limitations, the maximum
load that the boiler could carry was 24,500 kg/hr (54,000 lb/hr) or 70 percent
of rating.
Combustion of dRJDF—The combustion of the various coal:dRDF blends was
generally as good as the combustion of coal only. However, when the dRDF
substition was increased, the height, intensity, volume, and violence of
the fireball increased correspondingly.
When test firing the 1:1 blend and 100 percent aRDF, the fireball was kept
well away from the walls of the furnace by adjusting the overfire air.
Once these jets were adjusted for minimum smoke and maximum efficiency for
coal-only burning, they continued to meet the mixing and wall protection
requirements when burning blends and 100 percent pellets. As viewed from
the side of the furnace when firing both pellets and blends, the bed was
well burned out by the time it approached the front ash pit. The flame
pattern above the grate indicated that the fuel bed was maintaining proper
porosity and that the combustion was good. With little attempt to optimize
the system, a 10 to 12 percent carbon dioxide content in the flue gas at
the boiler outlet was readily obtained.
Fouling—An increase in the flue gas temperature as the boiler test progressed
indicated that the heat transfer sections had fouled somewhat. Inspection
of the furnace interior after the tests revealed that a light coating of
ash had accumulated on the tubes. Also, an interim boiler inspection
revealed that one-third of the rear wall of the boiler was covered with
slag. This slagging was subsequently eliminated when a spreader was adjusted
to prevent pellet impingement on the rear wall. Subsequent inspections of
the boiler after its being on-line for 8 days revealed that the slag had
sloughed off.
Clinkering—During the initial tests, frequent clinkering occurred on the
grate when firing a 1:1 blend. This clinkering was subsequently attributed
to a low hemispheric fusion temperature, 1204°C (2200°F), of the coal.
When the coal was changed to another coal having a higher fusion temperature,
114
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137 30C (250G°F), the clinkering stopped,
cures clinkered, che LOO percent pellets,
of 1151'C (2103°"), did noc clinker.
While coal with low fusion cc-mucra-
which had a low fusion temperature
Corrosion—Sight clamp-on corrosion case specimens '-ere installed on che
down-comers o: che rear screen wall 1.52 n (5 ft) above che fuel bed. After
478 hours of exposure to various blend and coal-only firings, normal wastage
was evident on all specimens except the 101S specimen. This test specj-en,
which had extremely high wastage, was laouncad in the area where the heavy
slagging occurred because of the maladjusted spreader.
3oiler Operation. Air Flow Controllers—During load shreds, the fuel bed
was more suscepcible co clinkering when coal:dRDF blends were fired. The
clinkering was elinir.aced by biasing the undecfire air control co supply
approximately 70 percenc excess air to the fuel bed. Reducing che ash
content of the pellecs to 10 to 12 percenc should eliminate all clinkering
problems and corresponding biasing of air controls.
Grate Dvell-Shake—Throughout che test, che duration and amplitude of che
grate shake pulse was adjusted to advance che fire line at the rear of the
boiler approximately 15.2 cm (5 in.) per excitation. In all advances, the
pulse frequency was che principal controlling variable. Ac 40 percenc load,
the frequency of che pulse decreased from 11 minutes for 100 percent coal Co
3 minutes for 100 percenc pellets. ^Tien firing a blend, the pulse duration
tended to increase because che bulk density of "he blend ash was less than
that of the coal ash.
Ash Handling—The sieve analysis of bottom ash samples caken during coal-
only, bland, and pellec-only firings indicated that conventional pneumatic
ash handling systems can handle the bottom ash from blend firings as well as
they do the bottom ash from coal-only firings. On a few occasions fire
occurred in che ash pit during blend firing. Rodding of che clinkers
revealed that the ash had a soft, pliable consistency. Under similar
conditions, when firing coal only, che bottom ash was much easier co break
up by rodding. The bottom ash removal system malfunctioned only during
100 percent pellet firing. The bottom ash was so fine that it would noc de-
entrain properly in the cyclone. These particles, which had been wected by
che steam in che ejector, passed chrou§n che chroat of che cyclone and
eventually plugged che ejector.
As dRDF was substituted for coal, che ash distribution became finer. The
size of the collector particles ranged from 200 micrometers for 100 percent
coal firing to 90 micrometers (sizes ac the 50th percentile) for 100 percenc
pellet firing. .Also, the carbon concent of che fly ash decreased signifi-
cantly with increasing dRDF substitution.
Mass Balance—The mass balance indicated that an unusually large amount of
the fuel ash had accumulated in the collectors. Subsequent analysis of che
collector fly ash revealed that the high collector ash weights were cue co
che presence of 50 co 70 percent carbon in the ash and that 90 percent of
che particles were greater than 50 micrometers in diamecar. The carbon
content of the bottom ash was 2 co 10 percent, and che carbon content of che
fly ash was 30 to 40 percent. The analysis of the fly ash as a function of
blend revealed chat its carbon content decreased as the cRDF substitution
increased.
Ifficiencies--During the testing, the boiler efficiencies were extremely
low, namely 52 co 60 percent. These low efficiencies were primarily due co
the low boiler loses (less than 30 percent of rating) and extremely high
115
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losses (up to 25 perccnc) of combustibles in the refuse. The analysis of
the results indicated that the coal-only and blend firing efficiencies had
no discernable differences. However, this fact is unique to the boiler
installation at MCI since the large amount of unburned combustibles removed
by the collectors is certainly an anomally to expected boiler performance.
Tables 1 and 2 present the results of the mass and energy
balances,
TABLE 1. HEAT BALANCE
SUMMARY
As Received
Blend 1:0
1:1
1:2
0:1
PARAMETER
Fraction of Rating .17
.33
.30
.19
Excess Air(%) 104
82
99
113
LOSSES
Dry Gas 17.9
13.7
17.8
19.4
Fuel Moisture .1
.9
1.2
4.0
H20 for H2 Combustion 4.0
5.1
5.4
8.1
Combustibles in Refuse 18.3
25.3
16.6
3.0
Radiation 3.7
1.8
1.8
3.7
Unmeasured 1.5
1.5
1.5
1.5
TOTAL 45.5
48.3
44.1
39.7
EFFICIENCY 54.5
51.7
55.9
60.3
TABLE 2. ASH MASS BALANCE
Bottom
Ash
Fly Ash
Collec tor*
Fuel
%
Ash in
Kg/h
r
Kg/hr
Kg/h
r
Blend
Flow
Ash in
Fuel
Carbon
With
Carbon
With
Carbon
With
Coal:dRDF
Kg/hr
Fuel
Kg/hr
Free
Carbon
Free
Carbon
Free
Carbon
1:0
872
21.9
191
82
89
5
r-»
r—
104
219
1:1
1489
23.3
347
232
238
5
6.8
110
369
1:2
2035
23.4
476
324
341
7
10.2
145
300
*Note: The collector weight was determined by difference.
Particulate Emissions. Mass Flux—The particulate mass flux in the 1:1 and
1:2 blend firings was slightly less than the flux in the coal-only firing.
However, the reductions were not significant at the 90 percent confidence
level. The mass flux at a 40 percent boiler load for 1:1 and 1:2 blend
firings was 0.5 g/Nm3.
Particulate Size—As more dRDF was substituted for coal, the particulate
diameter decreased. In the May tests the diameters for the coal-only
firings were 3 micrometers and those for the dRDF-only firings were
0.8 micrometer (at the 50 percentile point).
Particulate Resistivity—Because of the unusually high carbon content in the
fly ash during the coal-only firing, the resistivity was generally less than
10° ohm-cm. As dRDF was substituted for coal, the carbon burnout in the fly
ash improved and the resistivity increased to 2 * 1010 ohm-cm for the
1:1 blend firing.
Opacity—As dRDF was substituted for coal, the overall opacity of the plume
reduced signigicantly. At 40 percent boiler load, the opacity for coal-only
116
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firing was 16 percent (based on a 1.22 a (4 ft) diameter stack). Ac che sane
boiler load, the opacicy dropped to 10 percent for aRDF-only firing.
Gaseous Emissions. S03--Since che dRDF had a sulfur content of 0.6 percent,
the SOj emissions reduced with increasing dRDF substitution. The decrease
was particularly significant for the 1:2 and 0:1 (100 percenc dRDF) blend
firings. Ac 40 percenc boiler load, che S02 dropped from 1300 pom for coal-
only firing to 250 ppra for aRDF-only firing.
N0X—There '-ere no significant changes in N0X as dRDF was su'oscicuced for
coal. Ac 40 percenc boiler load, che NOx concentrations ranged from 200 co
350 ppm.
Chlorine—As dRDF '-as substituted for coal, che chlorine in the emissions
increased from 60 ppra for coal-only firing Co 650 ppm for aRDF-only firing.
As the boiler loads changed, che chlorine concentrations differed negligibly.
Fluorine—Fluorine concentrations also increased with increasing dRDF substi-
tution. However, the concentrations were very low, e.g., 3 pom for coal-
only firing and 12 ppm for dRDF-only firing at a 40 percent boiler load.
Hydrocarbons—There were no significant changes -in hydrocarbon emissions
when substituting dRDF for coal. Ac .a 40 percent boiler load, the total
hydrocarbons ranged from 10 to 25 ppm. As the boiler load increased, the
hydrocarbon concentrations decreased significantly.
Organic Emissions—The overall emissions of polycyclic compounds for coal-
only and blend firings were well below the chreshold limits proposed by che
National Academy of Science.
Inorganic Emissions—The analysis of che fly ash for trace tnecals revealed
chac relacive co coal-only firing che blend firing enriched some cecals buc
reduced ochers. For example, 34 times more lead was emitted when firing che
1:2 blend 'than when firing coal only. While dRDF was the main contributor
of 3r, MM, ?b ,• and Sb, coal was che primary source of As, Ni, and V.
Several elements, particularly As, Ga, Ma, and Sb, tended co concencraCe in
small particles. In addition, as the dRDF su'oscicucion increased, boch che
solubility of the fly and che amounc of small-size particulates in che
raspiracory range increased. Consequently, che combined effects of che
foregoing pose a pocencial hazard co respiracion and landfills.
SUMMARY
The preliminary resulcs from chese field tests indicace chac coal and dRDF
can be co-fired ac volumetric coal:dRDF ratios up co 1:2 wich only minor
adjustments to the boiler and fuel handling systems. The Phase 2 tasting,
which involved co-firing 1555 Mg of pellets at boiler loads of 40, 75, and
100 percenc and coal:dRDF volumetric blends of 1:1, 1:2, and 1:4 have been
completed. The tests were conducted in a Babcock and Wilcox spreader stoker
fired boiler rated at 68,000 kg/hr (150,000 lb/hr), 4312 PA (625 psi), and
440°C (325°F). Emissions tests were carried out to determine the effects of
blend firing on electrostatic precipitator performance with and without fly
ash injection. Results from this evaluation will be available in the near
future. The long-term effects of corrosion and erosion cn boiler tubes when
firing blends of coal:dRDF remains to be determined.
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CO-FIRING FLUFF RDF AND COAL IN A CEMENT KILN
Cliff R. Willey
Maryland Environmental Service
Maryland Department of Natural Resources
60 West Street
Annapolis, MD 21401
Prepared for the Conference
"Waste-to-Energy Update 1980"
Cincinnati, OH
April 15-16, 1980
118
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Co-Firing Fluff RDF and Coal in a Cement Kiln
Cliff R. Wiley
Fluff RDF from the 3altimore County, Maryland Resource Recovery
Facility was successfully tested as a supplemental fuel with pulverized
coal at the Lehigh Portland Cement Company, Union Bridge, Maryland. A
total of 1400 tons of RDF was burned in a 700 ton-per-day (clinker
capacity) rotary kiln, contributing 30 percent of the kiln heat. There
were four days of preliminary RDF burns followed by a 27-day extended
period of which 20 days involved burning RDF. Tests included air
emissions, cement quality and chemistry, RDF characteristics, and checks
on kiln operation.
Satisfactory Type I cement clinker was produced during most test3.
Evidence of reducing conditions on the kiln bed due to incomplete
burning of RDF in suspension was detected during initial tests; this
problem, however, was quickly corrected by increasing RDF velocity into
the kiln. Finely shredded RDF (roughly 95 percent less than one-inch
size) was required to guarantee suspension burning. The average heat
value of the RDF during the tests was approximately 6,500 3TU per pound.
So adjustment in kiln raw materials feed was required when burning RDF.
In general, particulate and chloride emissions were higher during
RDF burning, and S0X lower. Equipment configuration was such that only
stack emissions could be measured; therefore, the effect of burning RDF
on kiln emissions, versus effect on electrostatic precipitator efficiency,
could not be determined. After several days of burning RDF, some difficulty
was experienced in removing ash and cement dust from collectors in the
electrostatic precipitator; it va3 conjectured that this problem was
caused by a decrease in the resistiviy of airborne particles. The problem,
however, was not considered serious as adjustments in the precipitator
operation could be made to correct this situation.
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INTRODUCTION AND OVERVIEW OF TEST PROGRAM
In early 1975, during Che construction phase of the Baltimore County
Resource Recovery Facility (a joint venture of the Maryland Environmental
Service^/ and Baltimore County), Teledytie National, the project's prime
contractor, held discussions with more Chan 30 industrial firms,
institutions, and State organizations regarding their interest in burning
RDF to be produced at the Facility. As a result of this survey, letters
of interest were received from a number of potential users of RDF, three
of whom were cement companies. Of the three cement companies, attention
was directed to the Lehigh Portland Cement Company^/ Union Bridge,
Maryland, because of its large coal use (500 tons per day), interest in
a test program, and shortest distance (45 miles) from the 3altimore
County Resource Recovery Facility.
In ensuing discussions with Lehigh it became apparent chat, even
though there was interest in burning RDF, there were also a number of
justified areas of concern. These included:
a. abilicy to supply and feed RDF continuously
b. firing characteristics and ability to burn RDF in suspension
c. effect of RDF chemical composition and variations in
composition on cement quality and chemistry.
d. long-term effects of RDF on kiln operation and cement production
e. effect on air emissions
A test program was therefore developed Co tackle chese concerns step
by step, as follows:
(1) It was agreed that RDF would first be tasted at a
coal-fired, Lehigh-owned, lightweight shale kiln at
Woodsboro, Maryland. The advantage of this test
would be that experience could be gained with the
1/ A non-profit, waste management utility - an agency of the State of
Maryland
2/ Now a division of Heidelberg Cement Inc.
120
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burning characteristics of RDF and the reliability
of RDF feed equipment without facing concerns
about cement quality and production. As part or
the test, it was also agreed that the feed
equipment would provide seven days of continuous
operation before permission would be given to
begin tests at the cement plane.
(2) Provided there was satisfaction with the light-
weight aggregate test, RDF feed equipment would
be sec up at the Union Bridge cement plant to
produce test quantities of cement for analysis
(a 2 to 3 day test).
(3) Again based on satisfaction with the previous
step, an extended burn test involving air emission
measurements would be run.
Step (1) was carried out in 1977 and 1978 and Steps (2) and (3) in
March and November-December of 1979, respectively. This paper summarizes
results of these tests.
The test program was carried out by Teledyne National under contract
to the Maryland Environmental Service. Support for the program was
received from grants to the Maryland Environmental Service by the U.S.
Environmental Protection Agency and other sources, as recognized in
the Acknowledgment of this paper.
THE CEMENT INDUSTRY
Cement manufacturing presents an attractive opportunity for
energy recovery from solid waste via the RDF approach. It is energy
intensive, consuming 457 trillion 3TU per year(l)£/ and it involves
a process in which ash as well as other products of combustion become
part of the final product, thus minimizing residues requiring disposal
and need for costly additional air emission control equipment.
Duckett and Weiss(2) have reviewed the potential of this RDF market,
reporting that of L57 U.S. plants, 65 would have a capacity for 210 to
380 tons of RDF per day, 29 a capacity for 380 to 540 tons per day and
3/ Numbers in parentheses denote references.
121
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20 planes, over 540 cons per day when burning RDF as 30 percent of their
fuel supply, assuming 5500 BTU/lb. RDF and 300 operating days per year.
In addition, they point out that 26 plants are located within 25 miles
of major metropolitan areas. In spite of this attractiveness, progress
towards the use of RDF in che cement industry has been tempered by
industry caucion on one side and a lack of test information on the
other.
Cement manufacturing typically consists of the following steps:
(1) grinding and mixing raw materials in wet or dry form
(limestone, shale and/or clay, silicone oxide and
iron bearing materials)
(2) drying (primarily for che wet process)
(3) calcining (to burn off carbon dioxide from limestone)
(4) clinkering (or burning), a process that cakes place at
2,400 to 2,800°F (1,300 to 1,500s C)
(5) cooling, clinker grinding and addition of gypsum to
retard setting time
Although most new cement plants use a mora energy efficient preheated,
dry-process system in which only step 4, clinkering, is carried out
in the rotary kiln, 80 percent of existing plants still perform steps 2
through 4 in the rotary kiln(l). In this process, Steps 2, 3 and 4
occur in succession as raw materials from Step 1 are placed in one end of
the kiln and travel counter to the flow of heat and gases from fuel burned
at che opposice end. The process requires careful control of both
temperature and composition, which is adjusted to account for the ash
of fuels used to fire the kiln.
At the end of 1978, 63 percent of cement was produced with coal
or coke-fired plants, 20 percent with natural gas, and the remainder
with ocher energy sources. The trend in cement production is towards
coal-fired plants (1).
122
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TEST KILN
The Lehigh Portland Cement Company Union Bridge plane operates four
parallel 400-ft. (121-m), 11-1/2-ft. (3.5-m) diamecer, dry-process kilns,
each rated at 700 tons per day capacity clinker production. The Mo. 4
kiln was selected as the cest kiln. Characteristics of the kiln are as
follows:
a) kiln inclination - 5/8-inch (1.6-cm) per linear feet;
b) rotation - 65 to 85 rph;
c) fuel - bituminous Pennsylvania-type coal (12,000 BTU/lb.
and 2-1/2 - 3 percent sulfur);
d) fuel input - 6 cons per hour at 28 - 30 tons/hr. product
throughput;
e) reaction (burning) zone temperacure - about 2,700aF (1,480°C).
Air pollution control equipment on the test kiln (No. 4) consists
of two parallel Buell electrostatic precipitators (ZS?). Total flow
rate through the dual unit is 120,000 ACFH at 650"? (340°C).
Approximately 95 percent of Che ES? collected¦particles (ash and raw
material dust) is reinjected back into the kiln. The precipitators
exhaust to a common stack-
Raw aaterial feed to Che kiln consists of approximately 90 percent
limestone, 10 percenc shale, and small amounts of sand and iron bearing
materials.
To inject RDF into the test kiln, Lehigh placed a second nozzle
extending 11 feec (3.4 m) into the kiln, parallel co and under the coal
nozzle. Placement above Che coal nozzle would have increased RDF
suspension time, but kiln design prevented this arrangement. RDF
was conveyed co the nozzle pneumatically with abouC 3,200 ASCFM air ac
30 percent RDF kiln heat contribution.
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3ALTIM0RE COUNTY RESOURCE RECOVERY FACILITY AND RDF FEED STATION
Figure 1 shows che fluff RDF process line of the Baltimore County
facility as it now exists. Additional details on the facility and other
recovered materials are found in References 3, 4 and 5. Daily average
input to the facility is 750 tons residential solid waste per day. The
RDF production line has a capacity to produce about 300 tons per day RDF
under normal operating hours (10 hour day).
The 800 hp Williams secondary shredder was installed in October
of 1979; prior to that, secondary shredding was done with a 350 hp
Grundler horizontal hammermill. Approximate particle size distribution
of RDF for each of the shredders is given in Table 1. (This will change
somewhat with hammer wear and solid waste characteristics.) The
Grundler was fitted with a 1-inch round hole grate.
TABLE 1. RDF PARTICLE SIZE (NEW HAMMERS)
Screen Size Z Passing
inch centimeter Grundler Williams
3 7.6 100 99
2 5.0 100 98.5
1 2.5 95 94
1/2 1.3 51 84
3/8 1.0 17 57
In connection with the cement kiln tests, an evaluation was done
of secondary shredding to enhance RDF as a fuel for cement kilns;
this work is discussed in Reference 6.
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FIGURE 1. PROCESS FLOW FOR RJDF PREPARATION - BALTIMORE COUNTY FACILITY
PRIMARY SHREDDERS
(tvo 1000 hp A-60 Tracor Marksman
horizontal hammeraills, 6 x 12-inch hole graces
V
MAGNETICS REMOVAL
(two Dings three-stage belt
separators, one each shredder line)
V
DIVERTER
(Option: portion of primary shredded stream
can be diverted to Heil trailer compactor)
•»
AIR CLASSIFIER
(modified Montgomery Industries, Jacksonville 31ow Pipe,
vertical cylinder)
^ i
CYCLONE AND AIR LOCK FEEDER
*
TROMMEL
(Triple S 24-ft. (7.3-in), 12-fc. (3.7-m) diam. screen,
1.25-in. (3-cm) holes)
SECONDARY SHREDDER
(300 hp Williams horizontal hanmeraill, 1.5 x 2.12 inch hole,
herringbone pattern grates)
CYCLONE AND AIR LOCK FEEDER
Y
TRANSFER TRAILER COMPACTOR
125
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As part of a market development program associated with the Baltimore
County project, a modular, transportable RDF feed system was constructed
for receiving and pneumatically conveying RDF to various potential users.
Figure 2 outlines components of this system as modified for the cement
kiln tests. RDF is delivered in 65 cubic yard transfer trailers from
the Baltimore recovery faciliy and hydraulically metered into the RDF
feed system. Feed rates are controlled at the RDF feed module.
FIGURE 2. RDF FEED STATION
TRANSFER TRAILER
-------
LIGHT AGGREGATE KILN TESTS
Prior to conducting currant kiln casts, che reliability of RDF
feed equipment and burn characteristics of the RDF were demonstrated
for Lehigh at a nearby plant producing a lightweight aggregate from shale.
The advantage to this was chat It was unlikely RDF would affect the
quality of the aggregate.
At this plant, shale is heated and expanded in two 10-foot-diameter,
pulverized coal-fired rotary kilns. A.nozzle to inject RDF was added
to one kiln, next the the coal nozzle, and was connected via pipe Co
Che feed station set up outside, next to the kiln.
During February and March of 1977, 217 tons of RDF were burned
intermittently. Although there were initial problems with temperature
readings and shale buildup on the kiln wall, called "rings," these were
overcome by adjustments in the RDF nozzle position and in the kiln
controls. It was apparent in these Cest3 that rather finely shredded
RDF would probably be necessary to prevent the burning of RDF directly
on the kiln bed (grate sizes 4 to 1/2-in. were tried).
The RDF feed system (which differed from that in Figure 2 in chat
secondary shredding wa3 carried out at che kiln sice, wich RDF being
aspirated from the shredder and blown into che kiln chroug'n a 12,000 C7M
fan) did not prove reliable. Problems encountered were severe shredder
hammer wear and maintenance, jamming, uneven feed rates, and excess air
being blown into che kiln. Because of che inabilicy co feed RDF
satisfactorily with this system, modifications were made co che feed
system, bringing it into che configuration shown in Figure 2.
In October of 1978, using the modified equipment, cests were run
again at the kiln, sustaining an average RDF feed race of 1.13 cons per
hour, earning che permission of Lehigh co move che RDF feed station to
the Union Bridge cement plant.
-------
PRELIMINARY CEMENT KILN TESTS
The object of this test was to produce initial quantities of cement
clinker for analysis by Lehigh and by the Portland Cement Association
and to make any necessary RDF feed equipment adjustments. Tests were
run March 6 to March 9, 1979 and on April 26, 1979.
During the first test, 123 tons of RDF and 215 tons of coal were
burned in 55 hours of operation. The average heat contribution of the
RDF during this period was 24.7 percent. Cement clinker was sampled at
0, 10 and 30 percent RDF heat substitution.
During the tests, 13 transfer trailer loads of RDF were used. As
each truck was unloaded, a composite sample was taken for analysis for
heat value, percent moisture, and percent ash, according to ASTM procedures
D2015-71, D3302-74, and D3174-73, respectively. Results of these tests
are listed in Table 2.
TABLE 2. CHARACTERISTICS OF RDF - PRELIMINARY TEST
Characteristic and Unit Average Values3/ Low High
Heat Value, BTU/lb. 6897 5963 7832
Moisture, % 18.2 12.1 25.2
Ash, 7. 9.7 6.3 15.1
Metallic Aluminum, 1 0.018 <0.01 0.04
Sulfur, % 0.19 — —
f/Arithmetic average of 13 RDF samples except sulfur, which was run on a
composite of all samples
Samples of clinker and cement were analyzed by PCA by x-ray
fluorescence, x-ray diffraction, microscopic observation, and standard
ASTM C-130 cement tests. Partial data are included as Table 3 for
128
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reference by chose familiar wich cemenc chemistry and tests. From the
analysis, ?CA developed the following conclusions:
"The arnouncs of heavy metals found in che clinker vera very low
and ic does not appear that chese elements will cause problems
in praccice. Mo certain estimate of metallic aluminum could be
made, buc ic seems likely chac its concentration was negligible.
The RDF clinkers were of poor quality, mainly because of poor
control in che burning zone of che kiln. The burning zone should
always be maintained in an oxidizing state (at least 1 percent
excess oxygen) and none of the RDF should be allowed to fall into
the clinker before being thoroughly burned. If che burning
conditions are improved, ic seems to us chat good quality clinker
will result."
TABLE 3. CEMENT CHARACTERISTICS FROM PRELIMINARY RDF TEST
PERCENT RDF
Characteristics 0 10 30
Compressive Strength
3-day 3820 3620 4000
7-day 4650 4830 4370
28-day 5920 6200 5300
K20 0.69 0.72 0.90
Na20 0.06 0.11 0.14
t^O Equiv. 0.51 0.58 0.73
Free CaO 2.14 1.13 0.95
Although kiln operators were pleased with the testing and overall
control of RDF, there was concern about excess RDF burning on the kiln bed
ac che 30 percent rate, which caused reducing conditions, as noted in the
?CA analysis. Because of this condition, nozzle size was reduced from
9 co 7 inches in diamecer to increase RDF velocity and suspension cime.
129
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As a follow up co Che previous cesc, a one-day run was made on
April 26, in which 34.6 cons of RDF was burned. The smaller nozzle
increased suspension cime sufficiently Co minimize RDF burning on Che
clinker bed. In addicion co cescs ac 30 percenc, short runs were made
at 40 and 50 percenc RDF heat contribution. At 40 percent, RDF also
appeared to bum satisfactorily in suspension. However, at 50 percent
there was dropout and flaming pieces on Che bed and decreased visibility
into che kiln. Since a few hours of operacion is not enough co stabilize
for clinker testing because of the slow redistribution of ash chroughouc
the kiln and electrostatic precipitator system, no cement analysis was
done.
Following chese tests, permission was received from Lehigh to
proceed with the extended cement kiln tests.
To allow cine for installation of a larger shredder for secondary
RDF shredding and for equipment repairs at Lehigh, not related co the tests
but affecting them, further tescing was deferred until che fall of 1979.
EXTENDED RDF CEMENT KILN TEST
This test was run November 27 to December 23, 1979, burning 1,272
tons of RDF for an average race heat contribution of 30 percent
(approximately 3.5 tons per hour). Average characteristics of RDF used
in the tests are listed in Table 4. Table 5 summarizes coal usage and
RDF heat input during this period. There were 20 days on which RDF was
burned. During December 7 to 11 che kiln was on coal only for che emissions
testing program.
130
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TABLE 4. CHARACTERISTICS OF RDF - EXTENDED TEST
Characteristics ana Unit
Average Values f/
Low
Heat Value, BTU/lb
6440
5067 8797
Moisture, Z
20.4
6.7 39.0
Ash, %
11.8
6.4 27.7
a/ Arithmetic mean of 95 RDF samples
During December 5 though 14, the Environmental Engineering Division
of the Energy System Group of TRW, Inc., conducted source emission tests to
determine the amount of pollutants discharged from the electrostatic
precipitator serving the test kiln. There were seven sample periods, four
with RDF and three with coal only. Tests included flue gas flow rates
and stack moisture determinations, particulate matter and sulfur oxides
emissions, nitrogen oxides emissions, chlorides (as HCL) emissions,
stationary gas analysis, and flue opacity readings. All sampling was
conducted through four equally spaced openings located below the top of
the stack. No sampling could be done prior to gases entering the electrostatic
precipitator because of the design of the system.
Table 6 summarizes conditions during the emissions test, and Table 7
presents part of the test data. Because of electrostatic precipitator
failure during the first test day, December 5, that day's data have been
omitted.
During RDF burning, particulates were higher, chloride emissions
increased, nitrous oxide emissions appeared lower, and, surprisingly,
sulfur oxide emissions reached their highest levels, but remained well
within Federal and State standards. Since the RDF, which is only 0.2% in
sulfur, significantly lowered the overall sulfur content of the kiln
131
-------
fuel, the increase must have been related to some other changing condition
within the kiln or ESP. It was suggested that cleaning the ESP of dust,
which adsorbs SO2 and is recycled back into the kiln, prior to the tests,
may have produced this effect.
As of Che date of preparation of this paper, complete anal/sis of
the cement is not available from PCA. However, we have been told by
Lehigh chat cement strength tests and other analysis so far show a
satisfactory Type I cement was produced and indicate that the RDF fuel
had no detrimental effects on the cement.
Although there was an Lnitial concern by Lehigh that the raw material
feed to the kiln would need adjustment to compensate for differences
between the"'chemical composition of R.DF/coal ash and the coal-only ash
it replaced, this did not turn out to be the case. Therefore, to from
coal-only to coal-plus-RDF firing required few operational changes.
TABLE
5. COAL AND
RDF USAGE DURING
NOVEMBER - DECEMBER
TESTS
Date
Coal Usage
RDF Usa?e
% Heat
Daily Totals
Daily Totals
Total Heat Contribution
(Tons)
(Tons)
(Million 3TU)
(RDF)
11-27
72.70
61.5
799.5
31.17
11-28
72.85
59.0
767.0
30.78
11-29
106.0
92.3
1199.9
32.35
11-30
42.55
31.8
413.4
29.10
12-1
105.95
74.2
964.6
27.78
12-2
99.10
68.5
390.5
27.51
12-4
87.35
63.0
819.0
28.37
12-5
106.00
82.2
1068.6
29.37
12-6
89.20
70.3
913.9
30.21
12-11*
30.30
20.5
266.5
25.96
12-12
32.60
26.7
347.1
30.14
12-13
105.30
91.5
1189.5
31.40
12-14
104.20
90.7
1179.1
31.43
12-15
105.95
90.7
1179.1
31.11
12-16
109.30
90.9
1181.7
30.46
12-17
103.35
74.1
963.3
27.32
12-18
84.55
63.2
821.6
28.25
12-19
43.85
41.7
542.1
33.37
12-20
26.15
25.5
331.5
33.93
12-23
44.50
53.7
698.1
38.6
TOTAL
1721.4
1397.1
18,162.3
30.53
*Coal only
for emissions
testing 12-7 co
12-10
132
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TABLE 6. OPERATING CONDITIONS AND FUEL FEED DURING EMISSIONS TEST RUNS
TEST RUN NO.
2
3
4
5
6
7
Date
12/10
12/10
12/11
12/13
12/13
12/14
Tasc Time, scare
end
0913
1131
1211
1426
0950
1206
0840
1049
1412
1624
0801
1026
Product Race, cort/hr
29.2
29.4
28.9
25.1
27.1
29.2
Kiln, RPM
34
84
82
71
78
32
Coal Fuel Race, #/hr
12,200
12,770
11,800
3,600
3,430
8,500
Coal Fuel Type*
r/h-v
H-V
H-V
H-V
H-V
H-V
RDF Fuel Rate, ->l/hr
0
0
0
7,209
9,366
7,963
7. RDF by 3TU Value
0
0
0
30.6
37.4
33.0
Kila, Oxygen, Z
3.2
2.8
2.6
3.0
2.3
3.0
Xiln End Vacer Spray
(Gallons Per Miauce)
26
26
23
31
34
30
*R 3 Regular, H-V =» High
Volatile
Coal
133
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TABLE 7. CEMENT KILN EMISSIONS -
CONDITIONS STATED IN TABLE 6
TEST RUM
2
3
4
5
6
7
Flue Gas
Temperature, °F
485
486
483
485
500
493
Flow race, DSCFM
49,150
53,390
50,190
45,680
49,340
43,760
Water vapor, by volume
15.05
14.60
13.47
19.32
19.33
20.95
Stack opacity, %
2.6
17.0
9.8
21.6
16.8
16.6
Particulate Matter
Concentration, grain/DSCF
0.0128
0.0221
0.0331
0.0474
0.0801
0.0495
Emission rate, pounds per hour
5.38
10.12
14.26
18.56
33.83
18.56
Chloride Emissions as HC1
HC1, pom (dry)
7.47
191.
77.8
155.
223.
242.
, pounds per hour
2.09
58.0
22.2
40.3
62.6
60.2
Sulfur Oxides Emissions
SO3, pnra (dry)
3.0
2.5
9.3
4.1
25.4
7.1
, pounds per hour
1.83
1.65
5.79
2.32
15. 5
3.85
S02, ppm (dry)
19.7
34.3
. 235
1,050.
353.
444.
, pounds per hour
9.65
18.3
118.
478.
' 174.
194.
Nitrogen Oxides Emissions (as NO?)
N0X, ppm (dry)
135
295
112
72
130
160
, pounds per hour
47.6
113.
40.3
23.6
46.0
50.2
Stationary Gas Analysis (dry)
CO2, ?.
10.7
10.1
14.2
11.4
11.6
12.6
0-?, %
13 .8
13.6
9.9
11.1
11.5
11.9
CO, %
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
>?2, % by difference
75.5
76.3
75.9
77.5
76.9
75.5
134
-------
CONCLUSION
RDF proved co be an adequate fuel for firing with coal in a
rotary cement kiln ac races of up co ac lease 30 percent heat
contribution, "o detrimental effects on the cement quality were noted
once proper suspension burning of "he RDr was accomplished. Compression
test strengths- were generally the same or higher when RDF was burned.
ACKNOWLEDGMENT
This work was supported by the U.S. Environmental Protection Agency,
Grant S-30&786, "Marketing Refuse Derived Fuel," Office of Water and
Hazardous Materials, Washington, DC, and Grant R-305613, "Refuse Derived
Fuel as a Supplemental Fuel in Cement Kilns," Office of Research and
Development, MERL and IERL, Cincinnati, OH, Mr. Robert Olexsey, Project
Officer.
Significant contributions to Che project also were made by che Lehigh
Portland Cement Company, Teledyne National, and che Portland Cement
Association.
The author wishes Co thank Teledyne and Lehigh for "heir review and
helpful comments in che preparation of this paper.
Air emission casts were performed by TRW, Environmental Engineering
Division, Research Triangle Park, NC; RDF and coal analysis was performed
by Panniman and Browne, Inc., Baltimore, MD.
REFERENCES
L Portland Cement Association, "1973 Energy Report U.S. Portland
Cemenc Industry," Skokie, IL 60077.
2 Duckect, E.J., and Weiss, D., "The Use of RDF as a Kiln Fuel."
In press for ASME National Solid Waste Processing Conference,
Washington, DC, May 11-14, 1980.
3 Willey, C.R., and 3assin, M., "The Maryland Environmental Service/
Baltimore County Resoure Recovery Facility," Proceedings of che
Sixth Mineral Waste Utilization Symposium, Chicago, IL, 1973,
pp. 231-235.
135
-------
4 Bendersky, D. and Sinister, 3., "Research and Evaluation of Solid
Wasce Processing Equipment," Municipal Solid Waste: Resource
Recovery, Proceedings of Che Fifth Annual Research Symposium,
Orlando, FL, 1979, pp. 77-85.
5 Savage, G.M., et_. al_. , "Evaluacion and Performance of tiammermill
Shredders Used in Refuse Processing," Municipal Solid Waste:
Resource Recovery, Proceedings of the Fifth Annual Research
Symposium, Orlando, FL, 1979, pp. 36-98.
6 Weinberger, C.S., "Evaluacion of Secondary Shredding to Enhance
RDF Production as Fuel for Cement Xilns - A Research Test," In
press for ASME National Solid Waste Processing Conference,
Washington, DC, May 11-14, 1980.
136
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STEAM PYROLYSIS OF ORGANIC WASTES AS
A SOURCE OF CHEMICALS AND INDUSTRIAL FEEDSTOCKS
by
Michael J. Antal Jr.
Department of Mechanical and Aerospace Engineering
Princeton University
Princeton, New Jersey 08S40
INTRODUCTION
Recently completed research at Princeton University and elsewhere (1-4)
has shown biomass gasification to be a three step process:
1. Solid Phase Pyrolysis. At modest heating rates (l°C/min to 100°C/inin)
biomass materials lose between 70% and 90% of their weight by pyrolysis,
forming gaseous volatile matter and solid char. This weight loss occurs at
temperatures below 500°C. As discussed later, very high heating rates en-
hance volatile matter production at the expense of char formation. Recent
Princeton publications review mechanistic and kinetic research on cellulose
(5), lignin(6), and wood (7) pyrolysis in more detail.
2. Gas Phase Cracking/Reforming.of the Volatile Matter. At somewhat
higher temperatures (600°C or more) the volatile matter evolved by the
pyrolysis reactions (step 1) reacts in the absence of oxygen to form a
hydrocarbon rich synthesis gas. These gas phase reactions happen very
138
-------
rapidly (seconds or less) and can be manipulated to favor the formation
of various hydrocarbons (such as ethylene). Rates and products of the
cracking reactions for volatile matter derived from cellulose, lignin, and
wood are now becoming available in the literature (1, 3, 6, 7).
3. Char Gasification. At even higher temperatures char gasification
occurs by the water gas and Boudouard reactions, and simple oxidation
and hydrogenation:
C + H^O—>C0 + (water gas)
C + CO2 —^ SCO (8oudouard)
C + l/202->C0
(oxi dation)
C + o2 —*co2
C + 2!^—(hydrogenation)
Because pyrolysis (step 1) produces less than 30% by weight char for most
biomass materials, the char gasification reactions (step 3) play a less
important role in biomass gasification than steps 1 and 2. This contrasts
with coal gasification, where char gasification plays a much more important
role because most coals contain less than 40* by weight volatile matter.
The following sections discuss steps 1 and 2 of the gasification
process. This discussion assumes no free oxygen to be present in the gasi-
fication system, since oxidative processes seem likely to destroy the
chemical products sought by this research.
SOLID PHASE PYROLYSIS OF PARTICULATE BIOMASS
The work of 3roido (3), Shafizadeh (9), Lewellen (10) and others (11)
has shown cellulose pyrolysis to be describable in terms of a competetive
139
-------
mechanism*.
volatile tars (levoglucosan)
char + low molecular weight
volatiles
Two pyrolysis reactions compete to consume the cellulose; however only one
reaction produces char. The first reaction is favored by high temperatures
and rapid heating, producing combustible volatile matter (1evoglucosan) at
the expense of char formation. The second reaction is favored by low
temperatures and slow heating of the cellulose. Water, CO, CO^ and char
are the primary products of the second reaction.
Because char is an unlikely source of chemicals (having to compete
directly with coal), conditions which optimize the production of levoglu-
cosan (Cg 0^, or the "monomer" of cellulose) are of interest here,
levoglucosan (and related compounds) have been described as potentially
important industrial intermediate chemicals (12). In addition it plays
the role of a very reactive intermediate in the gas phase chemistry of
biomass conversion (step 2).
High yields of levoglucosan are obtained by rapid heating of the cellu-
lose polymer (13, 14) and when condensation reactions (leading to the forma-
tion of char) are minimized. Dilute phase, transport reactors minimize
condensation reactions by permitting the (gas phase) levoglucosan molecules
to rapidly disperse themselves in a largely non-reactive carrier gas (such
as H^O, CO^, H^, Ar, He, etc). Thus entrained flow, flash pyrolysis
reactors appear to be best suited for the production of large yields of the
140
-------
reactive intermediate "1evoglucosan" from cellulose.
A recent paper by Krieger (15) summarizes much of what is known about
lignin pyrolysis. Detailed studies of the mechanisms and kinetics are not
available. Char yields approximating 50* by weight are obtained when
lignin is heated at a moderate rate (100°C/min) to 500°C in steam. Rapid
heating reduces char formation (4).
As discussed in the following section, the volatile matter evolved
during lignin pyrolysis cracks rapidly in the gas phase to produce a
hydrocarbon rich synthesis gas. This gas phase behavior of lignin volatile
matter resembles that of the reactive intermediate 1evoglucosan, derived
from cellulose pyrolysis. Since the monomeric phenyl propane units which
compose lignin are joined by ether linkages (patterning to some extent the
glucosidic linkages which tie cellulose monomer units together), rapid
pyrolysis of lignin may result in the formation of monomeric phenyl propane
units. These reactive gas phase intermediates could undergo higher
temperature, gas phase pyrolysis to produce the permanent gases described
in the following section of this paper. Although the results of some
pyrolysis studies would seem to contradict this hypotheses (16), the
effects of secondary gas phase reactions may have masked the formation of
the primary intermediate molecule. Dilute phase, flash pyrolysis reactors
minimize the effects of secondary reactions and promise to be a powerful
tool for the study of lignin pyrolysis.
The pyrolysis chemistry of hemicelluloses has been reviewed by Soltes
and Elder (16). Although furan derivatives might be expected to be a pri-
mary product of hemicellulose pyrolysis, low yields are usually observed
relative to acetic acid. These results probably reflect the high reactivity
141
-------
of furfural and related molecules, which decompose rapidly by gas phase
pyrolysis. Consequently, reactive intermediates derived from hemicellulose
pyrolysis have not been observed. Nevertheless, results discussed in the
following section of this paper suggest the formation of a reactive inter-
mediate product during hemieel 1ulose pyrolysis which plays a role similar
to that of 1evoglucosan.
GAS PHASE CRACKING/REFORMING OF VOLATILE MATTER
DERIVED FROM PYROLYSIS OF BIOMASS
Siomass gasification chemistry is dominated by the role of the second-
ary gas phase cracking reactions, which are largely independent of the solid
phase pyrolysis reactions. A tubular quartz, plug flow reactor has been
used at Princeton (1-3, 6, 7) for two years to study the products and rates
of these gas phase reactions as a function of gas phase conditions (tempera-
ture, residence time, steam dilution, etc.). Our results show that gas
yields from cellulose can be increased by a factor of ten simply by in-
creasing the gas phase temperature from 500°C to 700°C with a gas phase
residence time of about 2 sec (1-3). Similarly, gas yields from Kraft
lignin can be increased by a factor of three or more by the same variation
in gas phase conditions (5). Table 1 lists typical product yields from
cellulose, mannose, and kraft lignin for reactor conditions chosen to
produce little or no condensible materials. Similar data for various woods
will be available in the forthcoming thesis of Mr. T. Mattocks (7).
Apparent gas phase rates of production of the major permanent gas
products of cellulose gasification are given as Arrhenius plots in Reference
1. Similar kinetic data for the gas phase conversion chemistry of lignin
142
-------
is given in Reference 6. Oue to insufficient funding, kinetic data for
hemicellulose gasification has not been obtained. However, kinetic data for
wood conversion will be presented in Reference 7.
TABLE 1. SELECTED GASIFICATION RESULTS FOR
CELLULOSE, D MANNOSE AND KRAFT LIGMIN
Cellulose 0 Mannose Kraft Lignin
Gas Phase Reactor Temperature
700
750
750°C
Gas Phase Reactor Residence Time
3.5
2.0
2.2 sec
Sample Weight
0.125
0.256
0.360 g
Char Residue Weight
0.012
0.053
0.176 g
Tar Residue Wei ght
0.003
0.011
0.052 g
Gas Volume Produced
84
31
73 ml
Gas Heating Value
490
455
579 Btu/scf
Calorific Value of Char
2.3
5.8
14.3 MM 3tu/tonne
Calorific Value of Gases
13.7
5.7
4.9 MM Btu/tonne
Calori fic Value of Tars
0.5
0.9
3.5 MM 3tu/tonne
Carbon 3alancs
0.96
0.37
0.98
Gas Analysis (Vol %)
CO
52
53
34
H2
13
10
1 5
co2
8
16
13
cha
14
14
32
C2H4
6
5
4
C2H6
1
1
1
C3HS
0.1
0.5
0.7
other
0.9
0.5
0.3
3ecause levoglucosan is known to be the major component of the volatile
matter derived from rapidly heated cellulose pyrolyzate, the large increase
in gas yields due to increasing gas phase temperatures may be presumed to be
the result of the gas phase pyrolysis of the reactive intermediate levoglu-
cosan. Similarly, the large increase in gas yields from lignin must be the
143
-------
result of the gas phase pyrolysis of some condensible material derived from
lignin. Although the identity of this intermediate compound is not presently
known, it may be presumed to be related to the phenyl propane units which
compose the lignin structure. Finally, the gas phase behavior of volatile
matter derived from mannose, wood and corn cob materials also suggests the
formation of an intermediate compound from the pyrolysis of hemicellulose,
which cracks in the gas phase to yield a product slate relatively similar to
that of levoglucosar derived from cellulose.
Somewhat surprisingly, strong similarities are evidenced between the
product slates of cellulose, lignin and hemicellulose in Table 1 . This
ability of thermal processes to "normalize" the conversion chemistry of
different biomass materials is an important advantage over the more feed-
Stock sensitive biological conversion routes.
DISCUSSION
Traditional feedstocks for the production of olefins (ethylene) and
other valuable chemicals are becoming scarce and costly. For example, crude
oil has recently been proposed as a feedstock for ethylene production by gas
phase pyrolysis in an unusual reactor (17). An alternative source of
ethylene is biomass: as described earlier six per cent yields of ethylene
from cellulose and woody materials by gas phase cracking are regularly
achieved at Princeton. With this yield, the yearly wood manufacturing
(27x10^ dry tons), cereal straw (161x10^ dry tons), corn stalk (142x10^
dry tons) and logging residues (75x10^ dry tons) available in the U.S.A. (13)
could be used to produce 24x10^ tons per year of ethylene without the use
of imported hydrocarbons. The predicted 1930 demand for ethylene in the
144
-------
U.S.A. is 14x10® tons. Thus, presently obtainable yields of ethylene from
organic wastes are sufficient to meet our annual ethylene demand by the gas
phase cracking of agricultural and wood residues.
Olefin production also has a significant impact on process economics.
Table 2 lists the values of various products obtained from 3razilian
Eucalyptus Wood using a Princeton pyrolysis reactor. Reactor conditions
weve not o-piirtizsd for sthylsns production. Nevertheless, ethylene is the
second most valuable product. Ongoing research at Princeton could more
than quadruple the yield of ethylene from Eucalyptus wood over that indicated
i n Table 1 .
CONCLUSIONS
Flash pyrolysis of particulate biomass materials produces large yields
of reactive intermediate compounds referred to as volatile matter. These
intermediate compounds undergo further pyrolysis in the gas phase at some-
what higher temperatures, producing lighter weight oxygenates and hydro-
carbons .
Research at Princeton has shown that yields of ethylene generally
exceeding by weight can be produced from cellulosic materials. The
ethylene is produced entirely by the gas phase cracking reactions. Future
research on the gas phase cracking chemistry of organic wastes could
potentially quadruple the yields of ethylene. The production of ethylene
and other valued chemicals from organic wastes has the potential of
revolutionizing the petrochemicals industry within a decade.
145
-------
TABLE 2. ESTIMATED VALUE OF THE PYROLYSIS PRODUCTS OF
BRAZILIAN EUCALYPTUS WOOD
One metric ton ¦
Eucalyptus Wood
GdS
-> C2Hu*
Char
Tar
9 Gj at S2 .00 per Gj = $1 8
32 kg at $0.38 per kg = $1 2
6 Gj at $1 .50 per Gj = $ 9
1 Gj at $1 .00 per Gj = $ 1
total $40
*Y1elds of ethylene will be considerably improved in future reactor designs,
REFERENCES
1. Antal, M.J. "The Effects of Residence Time, Temperature and Pressure on
the Steam Gasification of Biomass", American Chemical Society Division
of Petroleum Chemistry, Honolulu, 1979.
2. Antal, M.J. "Synthesis Gas Production from Organic Wastes by Pyrolysis/
Steam Reforming", IGT Conference on Energy from Biomass and Wastes,
Washington, D.C., 1978.
3. Antal, M.J., Friedman, H.L., Rogers, F.E. "A Study of the Steam Gasifi-
cation of Organic Wastes", (Final Progress Report, U.S.E.P.A.)",
Princeton University, Princeton, N.J. 1979.
4. Rensfelt, E., 81omkvist, G., Ekstrom, C., Engstrom, S., Espensas, S-G.,
Liinanki, L. "Basic Gasification Studies for Development of Biomass
Medium Btu Gasification Process", IGT Conference on Energy from 8iomass
and Wastes, Washington, D.C., 1978.
5. Antal, M.J., Friedman, H.L., Rogers, F.E. "Kinetic Rates of Cellulose
Pyrolysis in Nitrogen and Steam", to appear in Combustion Science and
Technology, 1979.
6. Kothari, V.S., Antal, M.J., Reed, T.B. "A Comparison of the Gasifica-
tion Properties of Cellulose and Lignin in Steam", to appear.
7. Mattocks, T. M.S.E. Thesis, Princeton University, Princeton, N.J., 1979.
8. Broido, A. "Kinetics of Solid Phase Cellulose Pyrolysis", in "Thermal
Uses and Properties of Carbohydrates and Lignins", Shafizadeh, F. et al .
(ed.), Academic Press, New York, 1976.
9. Shafizadeh, F., Groot, W.F. "Combustion Characteristics of Cellulosic
Fuels" in "Thermal Uses and Properties of Carbohydrates and Lignins",
Shafizadeh, F. et al. (ed.), Academic Press, New York, 1976.
146
-------
10. Lewellen, P.C., Peters, W.A., Howard, J.3. "Cellulose Pyrolysis
Kinetics and Char Formation Mechanisms", 16th International Symposium
on Combustion, Cambridge, 1976.
11. Arseneau, O.F. Can. J. Chem., 1971, 49, 632.
12. Shafizadeh, F. "Thermal Conversion of Biomass" in RANNZ, Volume 2,
NSF, 1 976.
13. Berkowitz-Mattuck, J.B., Noguchi , J.3. Journal of Agolied Polymer
Sci encs, 7, 709, 1 963.
14. Martin, S. "Oiffusion Controlled Ignition of Cellulosic Materials by
Intense Radiation", 10th International Symposium on Combustion,
Cambridge, Mass. 1964.
15. Graef, G., Allan, G.G., Krieger, B.S. "Rapid Pyrolysis of Biomass/
Lignin for Production of Acetylene", American Chemical Society Division
of Petroleum Chemistry, Honolulu, 1978.
16. Soltes, E.J., Elder, T.I. "Pyrolysis" in "Organic Chemicals from
Biomass", CRC Press, to appear.
17. Yamaguchi , F., Sakai, A., Yoshitake, M. and H. Saegura "COSMOS Cracks
Crude to Olefins", Hydrocarbon Processing, 9_ (58), 167, 1979.
13. Burwell, C.C. "Solar 3iomass Energy: An Overview of U.S. Potential",
Science, 199, 1041 , 1978.
147
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ENVIRONMENTAL ASSESSMENT OF w'ASTZ - TO-ENERGY
CONVERSION SYSTEMS
by
K. P. Aaanch
M. A. Golembievski
Midwest Research Institute
425 Volker Boulevard
Kansas City, Missouri 54110
EPA Contract No. 63-02-2166
MRI Project No. 4290-G
EPA Project Officer: Harry M. Freeman
for
Presentation ac the "Wasce-co-Energy Technology--rJpda te L980" Conference
Cincinnati, Chio
April 15-15, 19SO
148
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Introduction
The Fuels Technology Branch of Z?A13 Industrial Environmental Research
Laboratory in Cincinnati is sponsoring a program ac Midwest Research Insticuca
(MRI) co conduce environmental assessments or wasta-co-energy conversion facili-
ties. The overall objective or chis program is co evaluate the multi-media
environmental impacts chat result from using waste (municipal solid waste, in-
dustrial/sewage sludge, agricultural residue) as an energy source and to iden-
tify control technology needs. As part of chis program, MSI has undertaken
fairly extensive sampling and analysis efforts at the following waste conversion
sites.
* A 200 ton/day refuse pvrolysis system
* A 120 ton/day municipal Incinerator fired with municipal solid
vasts (MSW)
* 10MW power plant boiler fired with wood waste and No. 2 oil
* A 70,000 lb/hr 3team boiler fired with coal and densified refuse-
derived fuel (dRDF)
* A 20MW power boiler fired with refuse derived fuel
A brief description of the facility, the sampling and analysis methods used,
and the results obtained are individually presented below for each of these
facilities.
Refuse ?v~olvsis System
The Union Carbide refuse pyrolysis system (FJRQX) at South Charleston,
West Virginia, was designed to pyrolyze 200 tons/day of refuse. The refuse was
obtained by shredding MSV co a 3 in. size and then removing the magnecic mater-
ials from the shredded waste. The PUROX system is a partial oxidation process
chat uses oxygen to convert solid wastes into a gas having a higher heating
value (ZHV) of about 370 3tu/scf.
The refuse is fad into che cop of Che reactor, che principal unit on
the process. There are chree general zones of reaction within the reactor (dry-
ing, pyrolysis, ana combustion). The reactor is maintained essentially full of
refuse which slowly descends by gravity from che drying zone through the pyroly-
sis tone into che combustion zone. A countarflow of hoc gases, rising from the
combustion zone at che bottom, dries the incoming moisc refuse. As che material
progresses downward, it is pvrolyzed co form fuel gas, char, ana organic liquids
149
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Oxygen is injected into the bottom hearth section ac a ratio of about
207. by weight of incoming refuse. The oxygen reacts with char formed from che
refuse co generate temperatures of 2500 co 3000°; in che Lower zone which con-
verts che noncombusciblas inco a molten residue. This rasidue is discharged
inco a water quench cank vhere it corns a slag. The cypical composition of che
3 lag is reported to be 507. SiO-,, L17. Ai-,03, 117. CaO, 97. J^O, 57. FeO, 27. MgO,
and 27. ocher oxides.
The Sot gases from che hearch section are cooled as chey rise chrough
che zones of che reactor. Aftar leaving che raactor, che gases are passed
chrough a recirculating wacer scrubber. Entrained solids are separaced from
che scrubber wacer in a solid-liquid separator, ana racyclad co che reactor for
disposal. The watar product discharged from che separacor system is senc co a
plane creataent syscem. The gas leaving che scrubber is further cleaned in an
electrostatic precipitator and then cooled in a heat exchanger prior co combus-
tion in a flare comoustor. For purposes of this cast program, however, che pro-
duct gas was combusted in a package boiler and amissions resulting from its
operation were characterized. As a baseline comparison, the source boiler was
also tested when firad with natural gas.
Sampling and analysis of air emissions from che boilar included parti-
culate loading determination by EPA Method 5 with a aigh volume sampling syscam
(HVSS), gas analysis by continuous monitors for 0?) CO, hydrocarbons and M0X.
SQ2 was determined by EPA Method 6. Gas samples for total carbonyls were col-
lected using grab sampling techniques and analyzed using prescribed procedures.
In sampling for mercury and chlorides, fluorides, bromides and cyanides in the
vapor form, a sampling crain concaining 5 midget impiagers was used. In addi-
cion, che Source Assessment Sampling Syscam (SASS) was used as prescribed by
EPA for Level 1 environment assessment. Opacity of scack emissions was deter -
mined using EPA Method 9.
The PITR0X gas fad iaco che boilar was also sampled for cricaria pol-
lutants using EPA mechods.
¦ Refuse fed inco the reactor, slag from che quench cank, and wascavacer
before and after Creacnent were all sampled and analyzed for mecals, anions, and
PC3's. Wastewater analysis was also carried out for priority pollutancs ocher
chan ?C3's and for BOD, COD, curbidicy, phenols, acc.
Results of che casting effort showed that, of the criteria pollutants,
only N0X and particulate emissions increased when burning Purox gas as compared
to natural 2as. N0X and particulate levels were of the order of 350-400 pom and
6-14 mg/dNm respectively. SO2 amissions averaged 70-100 ?om. Particulate and
SO2 emissions vere below present scandards, whereas M0X will require further
-eduction. Also, analysis for cecals and ocher pollutants indicates that these
150
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should aoc present any problems. The vastevatar, however, without proper treat-
aeac would be a aajor araa of concern.
The SAM-LA assessment methodology vas utilised by applying it co che
daca obtained for aach of the thrae primary affluent streams from the Jurox pro-
cess (slag, scrubber affluent, ana boiler stack gas) . Results of this applica-
tion showed chat che scrubber afflueac had che highest degree of hazard, being
considerably greater than che hazard value for che inpuc river water. However,
che slag scream had che highesc toxic discharge raca (TuDR). The boiler flue
gas affluent had che lowesc hazard value and che lowesc TUDR; boch vera close
Co cha baseline values computed for boiler flue gas when burning nacural gas.
Municipal Incinerator Tired with MSV
The Braintree municipal incinerator (3raincrae, Massachusetts) is a
aass-burn facility consisting of tvia vacer-vall combustion units, aach with a
design capacity of 120 tons of MSW for 24-hr period. A portion of che steam
produced (20-357.) is supplied to neighboring manufacturers and cha remainder is
condensed. Each furnace is equipped with an ESP ana boch ISP's exhaust co a com-
mon stack.
The Riley Stoker boilers ara of the single pass design with aach hav-
ing a r3tad capacity of 30,000 lb of steam/hr at ±QQ°7 and 250/psig. The ESP
units ara single field, 12 passage precipitators with a specific collection araa
of 125 ft~/1000 acfa; aach has a design collection efficiency of 937..
invtronmencal assessment of the incinerator facility was conducted
using EPA approved sampling and analysis procedures. Results and conclusions of
tne cesciag effort are summarized below.
Of the critaria pollutants, S02> a:i(i hydrocarbon amissions were
low. However, CO levels were high and could not be explained considering the
large quantities of excess air chac were used. The average particulate concen-
tration was 0.24- gr/dscm, corrected co 127, CO2 • This level exceeded the faderal
and staca regulations. However, subsequent cases for compliance had an outlet
particulate loading o£ 0.07i jr/dscf, which shows compliance.
Elemental analysis of che glass-and metal-free boccon ash revealed an
overall increase in the elemental, concencracions when compared to the refuse faed.
The coiiactad fly ash contained levels of chlorides, sulfates and some trace
netals which nay be of concern. ?C3's were not detected in the collected fly
ash; & PAH compounds were identified.
Levels of 3CD,C0D, oil and grease, TS5 and TDS in the bottom ash quench
watar do not appear to be of concern. The phenolic concant vas found co be
<0.1 ag/liter in all samples.
151
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Levels of gaseous chlorides and ocher halides were low. Presence of
?C3's was confirmed only Ln the SAS5 era in XAD-2 resin ac a concentration of 3.5
ag/n'3.
Results of che SAM-LA environmental assessment procedure show che in-
cinerator scack emissions co have che highest apparenc degree of health hazard.
Further analysis is needed co determine che exact composicion of che organic
components of che scack emissions to better ascertain the hazard potential.
SAM-LA also shoved chac che boccom ash effluent had the largest toxic unit dis-
charge race due primarily to che abundance of phosphorus and aiecals in this stream.
Power Plant 3oiler Fired With vJoodwascs and Fuel Oil
The Mo. 1 unit ac the 3urlingcon Electric Plane (Burlington, Vennonc)
was originally a coal fired boiler which has since been aodiiied co fire wood
chips wich supplemencary No. 2 fuel oil. Because of che high aoiscure concent
of che chips, che boiler cannot provide che desired steam output on wood alone.
Therefore, No. 2 fuel oil is used. Sceam produccion-is raced ac LOO,000 lb/hr,
which powers a 10MW curbine generacor. Residual ash from che boiler is dis-
charged ac the end of che grace inco a hopper and is then pneumatically trans-
ported to an outdoor storage silo. The flue gases leaving the boiler are ducted
CO an amission control, system consisting of fao high efficiency mechanical col-
lectors in series. For a flue gas flow rate of 60,000 acfm at 330°?, che col-
lectors were designed for an overall pressure drop of 6.5 in. H2O and a collec-
tion efficiency of 97.75".
Sampling and analysis was focused on che input fuels, boctom ash, pri-
aary and secondary collector ash, and air amissions at the collector inlec and
outlet. The input fuels were analyzed for their heating value and trace cnecal
concenc. The aois cure concenc of wood was also decarmined. Boctom ash ana
collector ash were analyzed for cheir trace aiecai and PC3/PAH concencs . Collector
inlet gases were sampled using SPA Method 5 for parciculace. particle sizing and
elemencal analysis were also carried ouc. The scack gases were sampled and
analyzed for criteria pollutants, trace aiecals, and PC3/PAH. SPA Mechod 5 and
5ASS trains were used for parciculace aeasuraaenc. Major resulcs and conclusions
of the sampling and analysis program are as follows:
On a heat input basis, wood accounted for 807« of the boiler fuel, and
oil the remainder. The heat of combustion of wood was 5870 3tu/lb (as received)
and for oil, the heat of combustion was 19,500 3tu/l'o.
3octom ash analysis indicaced chac aosc elemencs were aore concentrated
in the ash relative co che input fuels. No PC3's were dececced in boctom ash but
one PAH compound was present at a concentration of 0.39 ug/g. Primary and secon-
dary collector ash contained no PCB's but several PAH compounds were identified
in the secondary ash wich one sample containing 10 ug/g of ahenanchrane.
152
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Particle sizing ac the collector inlat and outlet could r.oc be estab-
lished due co constant plugging of che dilution system. Scack concentration of
particulates averaged 0.08 gr/dscf and che collector had a particulate efficiency
of 9^.27.. N0X and SO? concentrations averaged 66 and 123 pon respectively. CO
averaged 213 pom and hydrocarbons 9 pom. Analysis of Method 5 particulate indi-
catad concancracicns approaching 100 ug/dsca for ?b, 3a, 3r, Fe and Ti in che
scack gases. ?C3 and PAH cases of che scack gases ware negative.
EPA'3 SAM-LA analysis indicated chac che 3accQdary collector ash con-
tained che highest degree of hazard a 1 chough all 3 ash screams were siailar in
che magnitude of cheir hazard values. Scack emissions snowed a low degree of
hazard. The primary collector ash had che highest toxic unic discharge rata.
However, because of che limitations of che methodology, chese. findings should
30c be viewed as conclusive.
Steam 3oilar Firad with Coal and Densifiad Refuse Derived Fuel (dRflF)
MRr, in conjunccion wich che Geaer3l Services Adniniscracion (GSA) and
che National Centar for Rasource Recovery (NCES) , conducted amission cases on
¦che No. boiler ac che GSA/Pantagon facility. The No. ^ unic was co-firad with
difieranc blends of coal and dSDF. S caam oucpuc of che underfed-racort stoker
boiler was rated ac 70,000 Ib/hr. The boiler was equipped wich. a mulciclone unic
for particulaca removal.
Emission casts vera conductad by MSI Co decarrine particulaca loadings,
gaseous criteria pollucanc and chloride concancracions in che scack gas. The
particulaca samples were also analyzed for lead. lasting was conducted first
at baseline conditions (coal only as fuel) and chen when firing blends of 20%
d&DF:S0" coal and 307. dSLDF:407. coal. NCXS. conducted other evaluations . The results
of MSI's efforts are as follows:
* Particulate emissions ware raducad from 22 to 387. when d3HF was
blended wich che original coal fuel. Filcarabla particulate emissions vera lowest
when using che 207. dSDF blend and rosa again when che proportion of dSDF was
raised co S07». This finding nay noc be conclusive, however, since che boiler
load was held staady during the 207. dSDF firing but not during che 607. mode.
* The amounc of particulaca lead amicced when burning cLJLDF with coal
is substantially higher than chat from combustion of coal alone (an average of
10C0 ag/a^ wits 207. dRDF, and i^50 ug/m^ with cC/L dSDF, versus 320 ug/n^ wich coal
only).
- Chloride amissions showed no definite trand which could be used to
correlate chloride amissions with RDF modes, though slightly higher concancracions
of HC1 were observed in r-o of che samples collected during combustion of che
507. dSDF bland.
153
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Power Boiler Fired with RDF
The Hempstead Resource Recover/ Plane (Long Island, New York) is a
complece wasce-co-energy facilicy in chac ic cakes In municipal solid wasce, pro-
duces an RDF and converts the fuel co eleccrical power. The facilicy consists of
cvo discincc segmencs: a refuse processing ooeracion, utilizing che 31ack Clawson
Eydrasposal system; and a power house, which concains cvo 5ceam. boilers aacL cvo,
20 eleccrical curbine generacors.
Tests were conducted by MRI on che Mo. 2 unic of che power house, which
is an air-swepc spreader scoker wacerwall boiler wich a nominal capacicy of
200,000 ibs/hr of sceam ac 625 psig and 750a7. The boiler was fired wich 1007,
refuse-derived fuei (RDF), although auxiliary oil burners are used for start-up
and during fuel feed incerrupcions. Air poliucion concrols for che boiler con-
sisc of a bank of 12 mechanical cyclones followed by an eleccroscacic precipicacor.
The purpose of che program was co primarily invescigate organic con-
stituents of- che scack gases and co quanciiy odorous componencs.
Emission screams avaluacad included che boiler boccom ash, cyclone ash,
ES? ash and che scack effluenc gases. Samples of che RDF were also collected for
analysis. The chree ash screams were analyzed for elemencal composition, as well
as for ?C3 and PAH oiacarials. Scack amissions were continuously aonitorea for
SO,, CO, 07 and cocal hydrocarbon concencracions, and were also cesced co
determine levels of vaporous mercury' and aldehydes. In addition, a test was con-
ducced using che Source Assessmenc Sampling Syscen (SASS) for analysis under
EPA's Level L protocol. Samples of che RDF fad co che boiler were avaluacad for
moiscure concent, elemental composition and chemical parameters (proximate/ultimate
analyses) .
Laboracory analyses have only been partially compleced. Therefore,
che results will be reported ac the cime of presencacion of this paper.
154
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EMISSIONS ASSESSMENT FOR
REFUSE-DERIVED FUEL COMBUSTION
Prepared for:
Environmental Protection Agency
Cincinnati, Ohio 45268
Under Contract No. 68—03—2771
Submitted by:
J.W. Chrostowski
Energy Resources Co. Inc. .
185 Alewife Brook Parkway
Cambridge, Massachusetts 02138
(617) 661-3111
March 18, 1980
156
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1. Introduction
Energy Resources Co. Inc. (ERCO) has been contracted
by the Environmental Protection Agency (EPA) to investigate
the emissions (gaseous and particulate) from co-firing of
refuse-derived fuel (RDF) and coal in a pilot-plant scale
atmospheric fluidized-bed ccmbustor (AFBC). Gaseous
emissions (SO.,, NO , CO, and hydrocarbons) are continuously
fa A
monitored with the appropriate instrumentation. Parti-
culates samples are collected with a Source Assessment
Sampling System (SASS train) and will be subsequently
analyzed for trace metals and organic content using the EPA
Level 1 procedure.
2. RDF/Coal Supplies
At the present time, two sources of RDF and a single
source of coal have been obtained. The suppliers and
properties of the fuels are summarized in Table 1.
3. Description of Work Plan
The major objectives of this investigation are as
follow:
• Quantify the gaseous and particulate emissions from
a co-fired RDF/coal feed in an atmospheric fluidized-
bed combustor. The primary process variables include
¦combustion temperature (1100 - 1400° F) and the
weight fraction of RDF in the feed (0-75 percent).
The upper temperature limit of 1400° F is set by the
fusion temperature of glass which is present in the
source RDF material.
157
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TABLE 1
COAL/RDF SUPPLIERS AND FUEL PROPERTIES
Crushed Coal
-FEEDSTOCK-
EcoFuel
Anierlcology
Suppller
Si ze
Heating Value (IIIIV, Btu/lb
m. f.)
Moisture (% wet basis)
Chemical Composition
(wt %, m.f.)
Sulfur
Carbon
Hydrogen
Ni trogen
Oxygen
Chloride
Ash
Fusion Temperature (°F)
Battelle
233S> 1. 7nm
59% mid-range
18%<300|jm
12953
9.38
0.07
71.81
1.78
1.59
15.5
0.53
Combustion
Equipment
Associates
28%<170 mesh
30% 170/230 mesh
42% 230/325 inesh
7827
3.2
0.61
40.0
4.6
<.1
45.5
.26
9.0
^1800
American Can
<1"
6430
25-35
N. A.
N. A.
N.A.
N.A.
N.A.
N.A.
N.A.
M 300
-------
• Obtain pilot plant performance data to assess the
suitability of co-firing RDF/coal in an atmos-
pheric fluidizea-bed combustor. This includes
the determination of associated heat and material
balances to define the overall process.
4. Description of Atmospheric Fluidized-3ed Combustor
(AFSC) Pilot Plant
A schematic of the ERCO AF3C pilot plant is provided
in Figure 1. The major equipment components include the
following:
Solids feed system (hopper, star valve and feed
screw)
Sutorbilt rotary vane air blower (600 SCFM at
6 psig discharge)
20" diameter fluidized bed (2.13 ft^) with
removable in-bed heat transfer tubes and ccn-
vective heat transfer tubes in the freeboard
Fisher-Klosterman cyclone for elutriated solids
collection
SASS train for particulate and organic collection
The fluidized bed has a Incallov-300 perforated plats
distributor which is mounted to permit thermal expansion.
The fluidizing medium is refractory sand with a mean particle
size of 400-500 microns diameter. The bed is heated to the
desired ignition temperature of 300-1000° F (before the
addition of the coal/RDF feed) by burning natural gas below
the distributor plate.
The continuous monitoring equipment for gaseous emissions
include the following:
159
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Cyclone
Convective
Freeboard
Tubes
Coal/RDF
Feed Hopper
ln-3ed Heat
Transfer Tubes
Rotary V
Star Valve
Solids
Feed
Screw
Distributor Plate
Combustion Air
Figure 1. Schematic of ERCO Fluidized 8ed Pilot Plant.
160
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• Seckman Paramagnetic C>2 Analyzer
• Thermo-Electron Chemiluminescent MO-NO^ Analyzer
• Thermo-Electron Pulsed Fluorescent SO2 Analyzer
• Beckman NDIR Model 365 CO/CO2 Analyzer
• Beckman FID Model 400 Total Hydrocarbon Analyzer
In addition to this on-line equipment, a Fischer Hamilton
Model 120 0 Gas Partitioner is used to periodically sample for
t t ^2' ^2' and CO2•
5. Summary of Coal/RDF Runs
The pilot-plant AFBC has been run with crushed coal
(no RDF) and with two RDF/coal mixtures (25 and 50 weight
percent EcoFuel) with bed temperatures ranging from 1000
to 1320° F. The operating data and the heat and material
balances for the individual runs are summarized in Table 2.
In these runs, the static bed height was maintained
relatively constant at 16 to 13 inches and the fluidizing
velocity ranged from 1.1 to 3.1 feet/sec at the actual operating
conditions. The minimum fluidization velocity for the refrac-
tory sand with a mean particle diameter of 420 microns is
nominally 0.29 feet/sec. Operation with a fluidizing
velocity 3.9 to 11.1 times the minimum fluidization velocity
ensures excellent solids mixing and uniform temperature
distribution (+ 25° F) throughout the bed.
It should be noted that these preliminary runs were
shake-down runs to ensure satisfactory operation of 1) the
pilot-plant equipment (solids feed system and bed operation);
161
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2) on-line instrumentation for SC^, ^x' CO, an<^ ^2 measure~
ment; and 3) evaluation of the SASS train for particulate
and organic collection.
The data in Table 2 for runs #3-6 with crushed coal
alone indicate satisfactory performance of the AFBC with
combustion temperatures ranging from 1150-1313° F. The
combustion temperature was varied by either changing the coal
and air feedrates (maintain same excess air) or the number of
in-bed tubes. Because of the fines in the crushed coal (18
wt percent less than 300 microns), 20 to 30 percent of the
carbon was burned in the freeboard. The efficacy of the SASS
train for particulate collection was initially evaluated in
run #6. Because of the relatively high particulate, loading
from the cyclones, the SASS train filter clogged in approx-
imately 30 minutes.
The two preliminary runs with EcoFuel/coal (run #7
with 50 percent RDF and run #3 with 25 percent RDF) at
nominally 1300° F were successful from the standpoint of
solids feeding and operation of the fluidizea bed. The run
(#7) with 50 percent RDF indicated a significant amount of
freeboard burning associated with the fine particle size of
the RDF (42 wt percent less than 230 mesh). The SASS train
was again evaluated in run #8 with 25 percent RDF; as before,
the filter clogged after about 30 minutes of sampling.
6. Future Work
The primary objectives of the future series of RDF/coal
runs will be the following:
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TABLE 2
SUMMARY OF RDF/COAL AF3C RUNS
RUN NUMBER
3
4
5
6
7
8
Feed Rates:
Coal/RDF (Ibs/hr)
71
12
30
30
24
34
Weight Fraction RDF
0.0
0.0
0.0
0.0
0.50
0.25
Air (SCFM)
115
71
56
64
39
59
Fluidizing Velocity
3.13
1.79
1.56
1 .66
1.10
1.64
(fps)
Temperatures (°F)
Bed
1203
1150
1318
1210
1320
1309
Freeboard
866
1086
905
891
1060
868
Stack Gas Composition
Oxygen (%)
1.7
3.1
2.9
3.7.
2.5
3.2
CO (pom)
1055
—
425
225
530
527
NO (ppm)
124
--
—
—
80
96
S0X (ppm)
975
—
—
—
539
273
Energy Balance
Heat Out/Heat In
1.02
1 .18
1.20
1.09
1.01 '
0.78
Thermal Efficiency
0.43
0.73
0,85
0.76
0.70
0.50
Combustion Efficiency
0.64
0.76
0.87
0.90
0.93
0.91
Fraction C Burned in
0.10
0.27
0.18
0.20
0.65
0.08
Freeboard
163
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Modify the SASS train to extend the sampling
time from 30 minutes to permit collection of
sufficient particulate and organic material for
subsequent analysis.
Run varying RDF/coal mixtures at temperatures of
nominally 1100, 1200, and 1300° F to obtain
gaseous emissions data. Run the SASS train with the
optimum set of conditions to obtain particulate and
organic emissions data. These runs will be per-
formed with the two RDF fuels presently available,
namely EcoFuel from CEA and the Americology fuel.
Obtain a source of hazardous waste which can be co-
fired with RDF to study emissions from an atmos-
pheric fluidizea-bed boiler.
164
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KVB12-P-
COMBUSTION AND EMISSION ASSESSMENT OF REFUSE-DERIVED
FUEL COFIRED WITH PULVERIZED COAL
BY
L. J. MUZIO, Ph.D.
J. K. ARAND
R. R. PEASE, II
KVB, INC.
A Research-Cottrell Company
for
WASTE-TO-ENERGY TECHNOLOGY - UPDATE 1980
Cincinnati, Ohio
April 15-16, 1980
166
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COMBUSTION AND EMISSION ASSESSMENT 0? REFUSE-DERIVED
FUEL COFTRED WITH PULVERIZED COAL
INTRODUCTION
Solid waste burning is not a new concept. Incinerators for burning municipal
waste were formerly common in most metropolitan areas. With the passage cf
stringent air pollution regulations and the advent ox the sanitary landfill,
burning of garbage has lost much of its widespread application. Recently,
however, new incentives have surfaced which make the combustion of municipal
waste an attractive disposal alternative. Today's proposed and prototype
waste-burning installations are processing solid waste Ln a variety of methods
that may shred, compact, or pelletize the refuse into valuable fuel. Resources
in the waste stream are recovered, and conservation of energy is realized by
the use of this alternate fuel.
A laboratory program is being conducted to measure emissions (aqueous, air,
solid waste) from the combustion of refuse-derived fuel (RDF) and mixtures of
RDF and coal in a suspension-fired system. Two sources of SDF will be eval-
uated, Combustion Equipment Associates' (CEA) Eco Fuel II and Americology SDF.
Evaluation of transformer waste oil contaminated with polychlorinated biphenyls
(PC3) is also planned. The criteria pollutants NO, SOj, CO, and hydrocarbons
will be monitored continuously in the flue gas stream, and special tests will
be performed to characterize the fuel, flue gas stream, and bottom ash in terms
of trace elements and trace organics including POM and ?C3, fluorine, chlorine,
and bromine.
The combustion facility used for this program is capable of firing gaseous,
liquid, and pulverized solid fuels. The basis of the combustion facility is
the shell of an 80-horsepawer firatube boiler which has been modified to fire
various fuels and also includes capability of air preheat (^-600 ?) , staged
combustion, and flue gas recirculation. The facility and burner used in
cofiring the coal and RDF are illustrated by Figure 1.
Testing is being conducted at a single load for all coal/RDF/vasts oil mixtures.
The burner settings which include primary/secondary ai.r ratio and burner swirl
are net being varied oarametrically but rather have been optimized in terms of
flame stability for each of the RDF/coal/waste oil mixtures. The combustion
parameters that are being investigated during the program include:
RDF Type
RDF/Coal/Waste Oil Ratio
Excess Air
Air Preheat
Staged Combustion Configuration
167
:
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TEST RESULTS
Included in this paper are the available gaseous and particulate results which
have been performed to date. Samples are currently undergoing analysis for
trace elements and organics and no results are presently available. The
results which will be discussed were obtained burning the CZA material cofired
with coal.
The gaseous data which were obtained are nitric oxides (NO), carbon monoxide
(CO), carbon dioxide (CO2), excess oxygen (02), unburned hydrocarbons (UHC),
sulfur dioxide (SO2) , chlorine (CI), fluorine (F), and bromine (Br). The
CI, F, and 3r were obtained only on certain test points, with all other data
obtained for each test point.
The gaseous emissions from the cofired coal and RDF are given in Figures 2, 3,
and 4. The NO emissions for single-stage combustion are shown in Figure 2; the
SO2 emissions are shown in Figure 3. It can be seen from these data that the
NO and SO2 emissions increase as the percentage of RDF is increased to
20 percent; emissions then decrease as the RDF fraction is increased to
50 percent. Based upon the RDF fuel analysis supplied by the manufacturer and
an independent testing lab analysis for the coal as given in Table 1, both the
NO and SO2 emissions should decrease as the RDF material is cofired with the
coal due to the lower nitrogen and sulfur content of the RDF.
The unburned hydrocarbon emissions for the cofiring points were essentially
0 ppm. The carbon monoxide amissions were lower with increasing percentages
of RDF than for coal alone, as illustrated by Figure 4. Typically, the emis-
sions were about 50 ppm lower at a ratio of 50 percent RDF and 50 percent coal.
The chlorine, fluorine, and bromine concentrations are shown in Table 2 for
all tests completed to date. Also included in this table are the particulate
loadings and 30^ concentration.
The loading results are consistent with what would be expected based on the
percentage of ash contained in the coal and the RDF, since there is less than
a percentage point difference in those ash values. The SO3 values for the
baseline coal are consistent with previous measurements that show a decrease
in SO3 concentration wirh staged combustion. However, this trend was reversed
when 50 percent RDF was fired. Additional measurements are necessary before
any conclusions can be made on the significance of this result.
The halogens show increased concentrations over the base coal when RDF is
cofired. The multiple values for Test No. D reflect that two separate samples
were taken at different times during the test and each analyzed. This probably
reflects the compositionality of the RDF. Also, the data shows a trend of
increasing halogen emissions as the percentage of RDF in the fuel is increased.
Again, additional tests are required before firm conclusions can be drawn from
these data.
163
KVB12-P-241
-------
ADDITIONAL TESTING
Further casting is planned to characterize the amissions from the cofiring
ox the Americolocy 3DF and coal. Also planned for inclusion with these tests
is the burning of transformer waste oil in combination with coal and RDF and
with the coal only. Results are anticipated by November of this year.
169
KV312-9-241
-------
o
to
I
I
ro
1. LiMI ' f*-' '*¦ _
III
0
u»r c«m
-------
900
300
700
600 —
>
a
500
m
O 400
Z
300
200 —
% 3DF
10%
O 1
~ 20%
O 50%
ot
10
12
EXCESS 02 PERCENT
Figure 2. Nitric Oxide Emissions Cafired Coal and
CEA SDF single Stage Combustion.
171
KV312-P-241
-------
TABLE 1
ULTIMATE FUEL ANALYSIS
Chemical Analysis
(Dry Basis) CEA RDF Coal
Carbon 39.32 74.17
Hydrogen 4.82 4.98
Nitrogen >0.1 1.34
Chlorine 0.29 0.04
Sulfur 0.74 1.05
Ash 9.71 9.33
Oxygen (Diff) 44.62 9.09
100.00 100.00
HHV, Btu/lb (dry basis) 7,754 13,206
172
XVB12-P-241
-------
% RDF
EV
T
0 2 4 5 8 10
EXCESS 0, psacsiT
Figure 3. Sulfur Dioxide Emissions Cofirsd Coal and RDF.
173
¦CV312-P-2 41
-------
360
320 _
5.5% 0^ Single Stage
Q 6% 0^ Single Stage
P"*| 4% 02 Single Stage
280 _
240 —
2- 200
u
Q
w
X
O
z
160
z
o
a
OS
-------
TJVBLE 2
Test No.
Excess
Oxygen
Particulate
Load tng
EO^
CIj
BR
F
Fuel
Type
Type
Firing
Condition
Percent
lb/106 Utu
ppm
ppm
ppra
ppm
A
5.4
2.29
3.04
14.2
0.09
3.0
Coal
Single Stage Coinb.
B
5.35
3.55
0
13.5
0.00
2.4
Coal
Two Stage Comb.
C
5.7
3.17
H/A
53.2
0.6
2.3
10* CEA RDF/
90* Coal
Single Stage Coin)).
D
6.5
3.4B
N/A
79.4
0.6
2.6
20% CEA RDF/
80% Coal
Single Stage Conib.
&
6
2.17
0
55.G2
0.15
14.0
50% CEA RDF/
50% Coal
Single Stage Couib.
F
5.0
2.28
4.4Q
79.4/
146.1
0.21/
0.07
5.71/
11.6
50% CEA RDF/
50% Coal
Two Stage Comb.
i
•u
to
I-4
-------
PILOT SCALE EVALUATION
OF FOUR REFUSE-DERIVED FUELS
R. A. Brown
Acurex Corporation
485 Clyde Avenue
Mountain View, California
176
-------
Abstract
Pilot Scale Evaluation of Four Refuse-Derived Fuels
R. A. Brown
The EPA is continuing to explore control technology in the
areas of alternate fuels, waste fuels and control of NOx emissions
for boilers in the government-owned test facility located at Acursx
Corporation.
Baseline tests on refuse derived fuels (HDF) fired either
with pulverized coal or natural gas were determined. Emissions
assessments made include NOx, CO, particulate loading and size dis-
tribution, twelve trace metals and a cursory search for ?C3 and
POMs. NO^ emissions decreased as the percent ?DF increased even
though the available fuel nitrogen increased. Particulate loadings
from the PDF were concentrated in the less than ly size fraction.
This project was supported by EPA Contract 53-02-1385. Mr.
H. M. Freeman was the project officer.
177
-------
PILOT SCALE EVALUATION OF FOUR
REFUSE-DERIVED FUELS
INTRODUCTION
There is considerable heating value (4000 to 7000 3tu/lbm)
associated with municipal solid waste. If this resource could be
used in steam boilers, rather than lost by incineration, a signifi-
cant energy resource would be tapped.
Research studies have included using heat recovery incin-
erators, spreader type stokers and suspension firing in large elec-
tric utility boilers. The EPA has supported experiments in cofiring
the refuse-derived fuel (RDF) in full scale boilers in St. Louis,
Missouri, Ames, Iowa, and Columbus, Ohio (References 1 through 4).
Although these full scale experiments are providing useful
data, problems associated with the many varieties of RDF need to be
studied. Because the refuse comes from local municipalities, there
can be significant variations in the combustion and environmental
characteristics of the fuel from season to season or from locale to
locale.
There is little published data on the emissions from RDF when
cofired with other fuels. Kilgroe (Reference 5) reported that the
St. Louis demonstration site produced a moderate increase in chloride
emissions but that the RDF did not significantly affect the S02 or
NO emissions. Little information is available on the amount of
x
trace metals and organics or the nature of the particulates. The
work performed here, provides the initial data base to answer environ-
mental questions on four RDF's.
178
-------
EXPERIMENTAL HARDWARE
The EPA experimental multiburner, furnace facility (Figure 1)
was developed to study control technology problems associated
with large-scale and utility and industrial boilers- Details on
this facility design have been discussed in other papers (References
5 and 7).
The furnace fires from 293 kW-thermal to 880 kW-thermal (1 to
3 x 10s 3tu/hr) depending on the fuel and heat release per unit
volume being simulated. The facility may either be front-wall
fired using one to five variable swirl block burners, or it nay be
comer-fired using four to eight tangentially-fired burners pat-
terned after Combustion Engineering's design.
The standard gaseous emissions (NO, CO, CO0^/ 30^) were
continuously monitored throughout the test program. Particulates
were obtained using a high volume EPA method 5 stack sampler; trace
metals and organics sampling was obtained using the Source Assess-
ment Sampling System (Reference 3).
The refuse-derived fuel tests were conducted in the main
firebox in the tancentially-fired mode. First, a feed system (Fig-
ure 2) was designed to control and measure from 10 to 60 lbs/hr of
varied refuse-derived materials. RDF is delivered to the upper
part of two diagonally opposed corner-fired burners. Natural gas
or coal is also delivered to these burners and to the other two
burners. The RDF feed system consists of a rotating drum hopper
which deposits the aiaterial on a conveyor belt. The conveyor de-
livers the material to a vertical downcomer, where it is pushed
through by a blast of air. Additional air at the junction of the
vertical downcomer and horizontal feed tube conveys the RDF into
the furnace through a horizontal water-cooled feed tube. The RDF
feedrata is controlled by a variable speed drive on the feed belt;
the drum is maintained at constant optimum speed to keep the feed
belt full.
179
-------
The delivery tube is sized to prevent blockage while mini-
mizing the transport air. This sizing is critical for a small-scale
facility where the minimum pipe size is governed by the maximum
particle size and the minimum conveyance air needed to keep the ma-
terial suspended. The received RDF material was shredded from a
nominal 2 to 4 inches down to 1 to 2 inches using a conventional
garden shredder to reduce the feed tube diameter and transport
air flow to an acceptable level.
EXPERIMENTAL RESULTS
The test program determined the gaseous, particulate trace
metal and organic emissions of refuse-derived fuel from San Diego,
California; Richmond, California; the Americology Facility in
Milwaukee, Wisconsin; and Ames, Iowa.
All of these materials had gone through metals and glass
separation and a primary shredding. Table I shows the composition
and heating value for each fuel type.
Figure 3 shows the effect of NO versus excess air for the
four fuels at 20 percent RDF and 80 percent natural gas. Although
the NO levels are not particularly high, there was a definite dif-
ference between the fuels. The NO also increases with both excess
air and increases in RDF. Also, when the percent RDF is increased
and cofired with coal, the NO levels decrease (Figure 4) while total
fuel nitrogen increases. This is possibly the result of enriched
fuel jets at the coal-refuse injection guns. Except at very low
excess air (5 percent) CO levels were always less than 100 ppm.
Results from the particulate, trace metal, and organics
sampling also provide some interesting preliminary information on
RDF emissions. Table II shows the results of particulate concen-
trations in the various size cuts for four RDF materials cofired
with natural gas. Although the total particulate quantity was
quite low in all cases, the majority of particles were smaller than
180
-------
ly and coll acted only on the filter. Although the particulate may-
be rather friable and break up in the sampling equipment during
collection, it may eventually end up in the respirable size range.
Table III shows particulate loading in the same size cuts for
two levels of Richmond RDF cofired with coal and for coal alone.
With the substitution of RDF, the total grain loadings decreased
with increasing RDF. However, in both cases, adding RDF increased
the percent of material in the lu size cut over coal alone. Thus,
it appears that adding RDF may increase the grain loading in size
cuts less than lu. This result could produce problems for flyash
collection equipment. Percent combustibles in the particulate
were generally Less than 2 percent except when the excess air
levels were 10 percent or less. This result also corresponds to
generally low CO (<100 ppm) and unbumea hydrocarbon levels.
Table TV lists the total trace metals in microcrams/3Cu
found in the particulates and the condensible vapor for: (1) coal
only, (2) coal plus 10 percent RDF, and (3) gas plus 10 percent RDF.
Increases in trace metal concentrations varied among the three
tests. In the coal only test, the lead concentration was exception-
ally high. In addition, no correlation was found as the percent
of RDF was increased.
It is difficult to draw any conclusions from this trace
metal data. Several factors may be contributing to the data vari-
ability:
• The RDF material is nonhomogeneous and will vary from
minute to minute, hour to hour, and season to season
• Metals from the furnace and sampling system could con-
tribute to the trace metal loadings
• Hold up in the convective section
• Analvtical error
181
-------
These factors indicate the need for a broader data base to
draw meaningful conclusions on trace metal concentration when co-
firing RDF with other fuels. This data will contribute to that
base, but a larger sample of data is needed to statistically de-
termine real trace metal effects.
In addition to trace metals, a limited search for organics
in terms of (PNA or PC3's) was undertaken. A portion of the par-
ticulate and the XAD-2 organic section resin of the SASS train were
analyzed by liquid chromatography according to EPA Level 1 procedures
(Reference 9). Of the material divided into the standard seven
cuts, only cuts two and three were expected to contain PNA and
PC3. Therefore, these two fractions were combined for a single
GC/MS analysis. Five out of nine tests where organic samples were
taken contained no detectable compounds. Test conditions, and the
PNA found in the remaining samples, are listed in Table V. Mo PCB
was found in any of the test samples.
Little organic material, combustible CO, and unburned hydro-
carbons were found in the particulate and gaseous streams. It has
been reported (Reference 5) that significant quantities of unburned
material have been found in full-scale tests. These pilot scale
tests have higher combustion efficiency over full-scale tests pos-
sibly because of the additional shredding and/or hot refractory
walls providing an improved ignition source.
In summary, up to 30 percent RDF may be cofired in a subscale
test facility without experiencing a reduction in combustion effi-
ciency. Additional studies are necessary to determine how this
technology can be implemented in a full-scale facility using the
same degree of efficiency but a higher RDF percentage. Furthermore,
the flame's heat transfer characteristics must be clearly defined
to determine the effect on the boiler steamside or to design a
boiler specifically for cofiring RDF. Finally, more data is needed
to statistically determine the trace metal and organic makeup of
RDF cofired boilers emissions.
182
-------
|EE/S 002c|
Fiyure 1. Photograph of experimental multiburner furnace.
-------
Feed System
Tangential Burner
Main Firebox
Figure 2. RDF feed system and firebox.
184
-------
20% Refuse/Natural Gas
0 Ames
g Richmond
& Americoiogy
lQ San Diego
% Ndmmf
200
.946
o
£ 100
10 20
30
0
EA%
Figure 3. Saseline i:Ox — amissions - HEP and gas.
185
-------
Richmond Reiuse/Pittsburg Coal
600
500
400
a 300
200
100
30
20
40
10
0
% RDF (Heat Input)
Figure 4. Effect of percent RDF coal and RDF.
186
-------
TABLE I. RDF FUEL ANALYSES
Ultimate Analysis*
Fuel Type
Pittsburg
No. 8 Coal
Klclnnond
Kefuae
Ames
Kefuse
Aiuerlcology
Refuse
San Diego
Refuse
Carbon X
75.23
42.60
40.49
40.29
38.01
Hydrogen X
5.15
6.26
6.01
5.88
5.64
Oxygen X
8.12
37.90
30.04
25.20
17.40
Nitrogen X
1.49
0.83
0.73
0.91
0.69
Sulfur X
2.51
0.16
0.35
0.17
0.21
At.lv X
7.50
12.25
22.38
27.55
38.05
Moisture X
(oa received)
0.93
23.8
15.2
24.4
26.3
Chlorine X
0.14
.46
.43
.72
.79
Heating Value
Utu/lb
13,545
7696
7831
7164
7146
A
Dry Baals
-------
TABLE II. EFFECT OF RDF TYPE ON PARTICULATE SIZE DISTRIBUTION
Filter
> 10 M
> 3 |i
>1M
Fuel
Qcy (gr/fc3)
X
Qty (gr/fL3)
X
Qcy (gr/ft3)
X
Qty (gr/ft3)
X
20X Ames
0.039
0.011
0.003
0.004
+ NaC Cas
(69)
(19)
(6)
(6)
20% Richmond
0.032
0.0004
0.0004
0.0024
+ NaC Cas
(91)
(1.)
(I)
(7)
20% Ainerico-
logy
+ Nat Gas
0.041
(86)
0.002
(5)
0.002
(5)
0.002
(5)
20% San Diego
0.062
0.007
0.002
0.006
+- Nat Gas
(80)
(9)
(3)
(8)
-------
TABLE III. EFFECT OF COAL AND RDF CONCENTRATIONS ON PARTICUI.ATE SIZE DISTRIBUTION
Fuel
Filter
>10ti
>3li
>lM
Qty (gr/fi3)
X
qty (gr/ft3)
X
Qty (gr/ft3)
Z
Qty (gr/ft3)
X
202 Richmond
RDF
+ Co.il
.026
(9.1)
.134
(47.3)
.107
(38.0)
.016
(5.5)
102 Kicliinonil
RDF
^ Coal
.0 44
(7-6)
.269
(46.1)
.226
(38.8)
.044
(7.6)
Coal Only
.021
(2.1)
.539
(56.3)
.344
(35.9)
.055
(5.7)
-------
TABLE IV. TRACE MliTAL CONCENTRATION FOR COAL VS 10% RDF + COAL VS 10% RDF + GAS (jig/Btu)
ELEMENT
Coal Only
10Z RDF + Coal
10% RDF + Gas
TeaC 040
Test 038a
Test tfllba
Cm
L. 9581
<0.3319
0.3402
Zn
0.5294
0.8227
0.4468
Mn
0.1526
<0.2693
0.0209
Pb
17.5319
0.3091
1.4996
Cd
o;oo9i
0.004 8
0.0062
lie
<0.0176
0.0013
<0.0034
T1
<1.7540
<0.0587
<0.0277
Sb
<0.0020
<0.0090
0.0333
Sn
0.1300
<0.0913
<3.5033
"b
<0.0015
<0.0173
<0.0009
As
<0.0881
<0.0323
<0.0184
d207. excess air
-------
TABLE V. 0RGA21ICS FOUND
Test Condition
Organic
Amount (ug/104 Btu)
Gas Coflre
Fluoranthene
10
10% RDF
Pyrene
332
20% EA
Ames Fuel
Gas Coflre
Phenanthrene
64
10% RDF
Fluoroanthene
160
20% EA
Pyrene
576
Richmond Fuel
Dlphenyi Elher
3395
Blphenyi Phenyiether
1697
Gas Coflre,
Phenanthrene
59
10% HO*
Pyrene
104
2C% EA
M.Tiericology F-.el
Coal Coflre
Ptienanthrene
98
10% RDF
20% EA
191
-------
REFERENCES
1. Vaughan, D. A. and Associates. Report of First Year Research
on Environmental Effects of Utilizing Solid Waste as a Supple-
mentary Powerplant Fuel, Battelle Columbus Ohio Laboratories,
EPA Research Grant R-304008, June 1975.
2. Nydick, S. E. and Hurley," J. R. Study Program to Investigate
Use of Solid Waste as a Supplementary Fuel in Industrial Boilers,
Thermo-Electron Corporation. EPA Contract Mo. 63-03-3005,
January 1976.
3. Riley, B. T. Reliminary Assessment of the Feasibility of
Utilizing Densified Refuse Derived fuel (DRDF) as a Supplementary
Fuel for Stoker Fired Boilers, published report to EPA, 1975.
4. Vaughan, D. A., Krause, H. H., Hunt, J. Cover, ?. W.,
Dickson, J. 0., and Boyd, w. K. Environmental Effects of Utili-
zing Solid Waste as a Supplementary Powerplant Fuel. Seventh
Quarterly Progress Report, EPA Research Grant 304008-02-1, 1975.
5. Kilgroe, J. D., Shannon, L. J., Gorman, P. Environmental Studies
on the St. Louis Union Electric Refuse Firing Demonstration.
6. Brown, R. A., et al. Pilot Scale Investigation of Combustion
Modification Techniques for N0X Control in Industrial and Utility
Boilers. iPA-600/2-76-152b. Proceedings of the Stationary
Source Combustion Symposium, Volume II, June 1976.
7. Brown, R. A., et al. Investigation of Staging Parameters for
NOx Control in Both Wall and Tengentially Coal-Fired Boilers.
EPA-600/7-77-073C. Proceedings of the Secondary Stationary
Source Combustion Symposium, Volume III, Stationary Engine,
Industrial Process Combustion Systems, and Advanced Processes,
July 1977.
8. Blake, D. Source Assessment System Design and Development, EPA-
600/7-78-01S, August 1977.
9. IERL/RTP Procedures Manual: Level 1, Environmental Assessment,
Second Edition. June 1976.
192
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APPLICATION OF SLIPSTREAMED AIR POLLUTION
CONTROL DEVICES ON WASTE-AS-rUEL PROCESSES
Fred D. Hall, John M. Bruck, and Diane N. Albrinck
PEDCo Environmental, Inc.
Robert A. Olexsey
U.S. Environmental Protection Agency
INTRODUCTION
PEDCo is currently involved in an EPA contract for testing
and evaluating prototype air pollution control devices on various
waste-as-fuel processes for the control of potential harmful air
emissions. As part of the contract, sampling and analysis pro-
grams were conducted at the RDF and coal cofiring facility in
Ames, Iowa and the mass burn incineration facility in Braintree,
Massachusetts. These programs involved evaluating the pollutant
removal efficiency of a pilot fabric filter, a pilot scrubber,
and a pilot ESP. The objective of the program was to determine
pollutant removal efficiencies of each device for variable proc-
ess and control device operating parameters. Operation ana
testing of the control devices took place in October and November
1978 and June through October, 1979.
This project focused on three primary thermal waste-as-
fuel technologies: 1) Co-firing - The combined firing of a
solid, largely cellulosic waste with coal, oil, or natural gas in
a modified conventional boiler, 2) Mass burn incineration - The
combustion of unprocessed or processed solid wastes in water-
wall incinerators for the generation of steam, ana 3) Pyrolysis -
The thermochemical decomposition of solid wastes in an oxygen-
starved environment that converts a heterogeneous waste material
into a liquid, gaseous, or solid fuel product.
These technologies were studied with respect to atmospheric
pollution and potential control techniques in various phases as
follows: 1) Collection of data on known and potential air pollu-
tants for waste-as-fuel processes, 2) Assessment of air pollution
control devices applicable to waste-as-fuel processes, 3) Deter-
mination of the best air pollution control devices to be de-
veloped as pilot-scale air pollution control devices for the most
194
-------
significant problems associated with waste-as-fuel processes, 4)
Procurement of two to four pilot-scale air pollution control
devices, and 5) Operation of the pilot-scale units to generate
and analyze data-
Midwest Research Institute (MRI), concurrent with the PEDCo
effort, conducted a comprehensive environmental assessment of
various resource recovery operations for EPA. Data from this
project provided valuable technical information for the PEDCo
study with respect to test site and control device selection, and
air pollution problems associated with waste-as-fuel processes.
PRELIMINARY PROGRAM
The nature and magnitude of atmospheric pollutant emissions
from waste-as-fuel processes were investigated as were the
requirements for emission control technology. The focal point of
the study was the combustion process. Pyrolysis processes are
still under development and no continuously operating systems
were available for testing. Therefore, pyrolysis was not of
primary interest in this project.
Waste preparation (preprocessing) as well as the combustion
process were studied. Particulate was the most apparent problem
associated with waste preprocessing but for the combustion proc-
ess, trace elements in the particulate as well as gaseous chlo-
rides and mercury vapor were also cf interest. Previous studies
had theorized that there logically should be an increase in
particulate emissions when co-firinc RDF and coal versus coal-
firing alone because of the normally greater ash content of RDF
versus coal and an expected decrease in control device efficiency.
Although the MRI study did not show a definite increase in par-
ticulate emissions for co-fired boilers, gaseous chlorides as
well as trace elements in the particulates such as lead, copper,
and zinc were shown to increase when burning RDF plus coal versus
coal alone while others, such as iron and calcium were shown to
decrease.
From an air pollution control technology standpoint, PEDCo
investigated state-of-the-art technologies (e.g., fabric filter,
ESP, and scrubber) for control of waste-as-fuel processes as well
as more novel devices (e.g., wet ESP's, jet ejector scrubbers,
etc.). Fabric filters have been successfully applied to prepro-
cessing operations and ESP's are the most common air pollution
control equipment used cn co-fired boilers and mass burn incin-
erators. Full scale fabric filters have not been applied to
waste-as-fuel combustion processes and wet scrubbers have been
195
-------
used on incinerators with less success. Since state-of-the-art
devices effectively controlled pollutants of concern from waste-
as- fuel processes, the other more novel devices were not considered
for the PEDCo test program.
TEST PROGRAM
Early in the project, several waste-as-fuel facilities were
visited as a prelude to later, more extensive test site selection
and to observe the effectiveness of the applied control technolo-
gies. Table 1 describes those sites visited.
TABLE 1. PEDCo RESOURCE RECOVERY SITE VISIT SUMMARY
Generic
technology
Plant
location
Preprocessing
product
Preprocessing
Missions
control
ROF
combustion
equlonent
Casbustlon
enlssion
control device
Co-Mr1ng
Ants. Iowa
Chicago SW
Colimbus. Ohio
Hagentowi, MO.
Milwaukee. Wis.
Fluff
Fluff
Shredded wste
?ellets
Fluff
Saghouse system
Saghouse system
None
•lore
lagftouse systen
Pulverized coal and
stoker-bol ler
Pulverized coal
boiler
Stoker-boiler
Stoker-boiler
Pulverized coal
boiler
ESP
ESP
Cyclone
Cyclone
ESP
Mass burn
Chicago. Ntl
Harrliburg, P».
Nashville, Tenn.
Saugus. Mass.
Hamilton, Ontario
Jraintree, Mass.
Bulky Itens
removed
Sulky iten
rwoved
Sulky Items
removed
As received refuse
Pulverized refuse
As received refuse
.lot Applicable
Hot applicable
Not applicable
Not applicable
None
Not applicable
Incinerator/boiler
Inc1nerator/bo1ler
Incinerator/boiler
Inclnerstor/boi1er
Inclnerator/boller
Incinerator/boiler
ESP
ESP
ESP
ESP
ESP
ESP
Pyrolysls
South Charleston,
W. Va.
Shredded waste
None
Open burner
None
Other
Fairmont, M1nn.
Houston, Texas
Minneapolis, Minn.
Shredded waste
Shredded waste
Oevatered sludge
None
Bagnouse
None
Inc1nerator/bo1ler
Cement kiln (co-
fired with gas)
Multl-hearth sludge
Incinerator
Wet scrubber
Wet scrubber
None
From these sites, the Ames, Iowa cofiring facility and the
Braintree, Massachusetts incinerator were selected as test sites
because of the cooperation of the management, availability of
data from the MRI source assessment project, high reliability of
the preprocessing and utility operations, and limited facility
modifications required.
196
-------
The execution of a program of this type relies heavily on
the cooperation of plant management. The administrative, oper-
ating, and maintenance staffs of the Ames Municipal Electric
System and the Braintree Municipal Incinerator provided EPA and
PEDCo with invaluable assistance throughout the program.
' Concurrent to the site selection process, available pilot
air pollution control devices were investigated. Suitable pilot
ESP's and scrubbers were available from vendors and IZRL/RTP. A
transportable pilot fabric filter typical of a full scale unit
was not available for the test program. Since the fabric filter
testing was to be an integral part of the test program, a 1.4 nvVs
(3000 acfm) pilot fabric filter was designed and assembled by
PEDCo for IERL/Cincinnati.
The project objective for both test sites was to character-
ize the specific pollutant removal efficiencies of each control
device for. different boiler loads, RDF inputs, and operating
parameters. It has been assumed that any full-scale application
of these control devices to a coal- and RDF-fired boiler must
operate with varying flue gas temperatures and compositions. A
plan was developed to monitor and measure these two factors, but
not co modify or control them.
The IZRL/RTP mobile ESP and scrubber as well as the IZRL/Cin-
cinnati pilot fabric filter were slipstreamed on Ames' 3oiler 7.
The scrubber and ESP were tested in October and November 1973
while the fabric filter was tested in June and July 1979. Ames
Boiler 7 is a tangential fired pulverized coal unit with a 33 MW
capacity. During the test program, RDF supplied from 0 to 25
percent of the total boiler heat'input. The scrubber was tested
both upstream and downstream (primary and secondary) of the exist-
ing full seals ESP and the mobile ESP and fabric filter were
tested only as primary devices.
At Ames, total uncontrolled particulate emissions did not
appear significantly different when comparing coal only tests to
coal plus RDF tests. Some uncontroleed trace elements and
gasecus chlorides increased significantly when burning RDF plus
coal. Lead and zinc amissions concentrations were about 3 times
higher and gaseous chlorides emission concentrations were about
ten times higher when burning 2 5 percent RDF plus coal than when
burning coal alone.
The scrubber operated at pressure drops of 25.4 and 76.2 cm
(10 and 30 in.) H2O. The particulate removal efficiency of the
scrubber was consistently above 9 9 percent when used as a primary
device but considerably less (72 to 97 percent) when used as a
secondary device. The particulate removal efficiency of the ESP
ranged from 94 to 98 percent ana cf the fabric filter above 99
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percent. Neither scrubber, ESP, or fabric filter particulate
removal efficiencies changed appreciably as the portion of heat
input supplied by RDF increased. The efficiency of trace element
removal was typically less with the scrubber than with the ES? or
fabric filter. For example, lead removal efficiency was about 90
percent with the scrubber, but greater than 95 percent with the
ESP and fabric filter. Alternatively, the gaseous chloride
removal efficiency was greater than 95 percent for the scrubber
but negligible for the ESP and about 20 percent for the fabric
filter.
At Ames, the full scale fabric filter controlling the pre-
processing. system was tested to determine its particulate removal
efficiency. The fabric filter controlling the 140 Mg (150 tons)
per eight hour day plant operates at 22.4 m^/s (47,000 acfm) and
collects the in-plant air via hoods located at critical dusting
points, 'especially transfer points. The cleaned air from the
fabric filter is discharged back into the resource recovery
plant. The tests showed average inlet and outlet concentrations
of 44 6 mg/m3 and 9.7 3 mg/m^ respectively for an average particu-
late removal efficiency, of 97.8 percent.
The IERL/Cincinnati pilot fabric filter and a pilot venturi
scrubber from Neptune/Airpol were slipstreamed as primary con-
trols on the Braintree Municipal Incinerator. These control
units were tested August through September 197 9. The Braintree
plant has two waterwall incinerators with a design capacity of 5
tons of unprocessed refuse per hour each. Incinerator No. 1
which operates continuously was used for testing, and it is
controlled by a Wheelabrator-Frye ESP.
The pilot fabric filter that was tested at the Ames site was
transported to Braintree and slipstreamed upstream of the full
scale ESP. The fabric filter was automatically operated and
functioned 24 hours a day. By varying operating conditions of
the fabric filter and maintaining steady-state conditions at the
furnace and boiler, the control performance of the fabric filter
was evaluated with respect to: precoating, pressure drop, air-
to-cloth ratio, and cleaning mechanism. A lime precoat was added
to the flue gas stream during some of the tests upstream of the
fabric filter but downstream of the inlet sampling location. The
pressure drop across the fabric filter ranged from 3.9 to 15.8 cm
(3.5 to 6.2 in.) of water. The cleaning mechanism was reverse
air, shake, or both. Varying the air-to-cloth ratio from 1.1 to
2.0 did not significantly effect the pollutant removal efficien-
cies. The cleaning mechanism also did not appear to have a
perceptible affect on performance, however the amount of time
necessary for each mechanism varied. Shaking took the longest,
reverse air next and both took the least amount of off-line
cleaning time. The particulate removal efficiency averaged 95.2
percent for all tests. Most trace element removal efficiencies
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were consistent with the particulate removal. Sulfur oxides were
not effectively controlled by this device, however precoating the
fabric with lime roughly doubled the SOx removal efficiency (20
to 40%), when compared to the "without precoating" tests. Gas-
eous chloride removal efficiency for "without precoating" tests
a\feraged 23 percent, and increased to 38 percent with the lime
precoat.
The scrubber used at this site was a pilot venturi scrubber
rented from Neptune/Airpol. It was installed on Braintree's
incinerator no. 1, using the same slipstream duct work as the
pilot fabric filter. The pilot scrubber operated unfiltered,
recirculating scrubber liquor. The pH was controlled through
addition of soda_ash. The liquid-to-gas ratio ranged from 5.5 to
18.4 gal/1000 ft and the pressure drop ranged from 10 to 32 in.
H2O. The particulate and trace metal removal efficiencies for
the scrubber were much lower than the pilot fabric filter, how-
ever, gaseous chlorides were removed with 96.5 percent efficiency.
The scrubber tests showed some re-entrainment of particulate
in a few'of the runs due to poor demister removal of water
droplets. The particulate removal efficiency averaged 72 percent
during tests in which re-entrainment was minimized.
In summary, the fabric filter performed more effectively
than the scrubber in removing particulate pollutants but not
gaseous compounds.
Currently, ail field and analytical work is completed on
this project. One report entitled "Evaluation of Fabric Filter
Performance at Ames Solid Waste Recovery System" is in preliminary
draft stage and evaluates the particulate control achieved by the
fabric filter at the Ames RDF plant. Two other reports are
presently being prepared, one covering the evaluation of the
mobile ESP, scrubber and fabric filter tests conducted at the
Ames Power Plant, and the other report will discuss results of
our tests of the mobile fabric filter and scrubber at the Brain-
tree mass burn incinerator.
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TREATMENT OF WASTEWATERS "ROM
REFUSE-TO-ENERGY SYSTEMS
3Y
GORDON P. TREWEEX, Ph.D.
MEMBER ASCE
ABSTRACT
This paper discusses the wastewater treatment technologies that can be
effectively utilized at WAF facilities to treat waterborae pollutants. The
principal water-borne emissions contain organic surrogates (BOD, COD, TSS)
in concentrations up to 100,000 mg/1 at pyrolysis units; organic priority
pollutants in concentrations up to 100 mg/1 at pyrolysis and digester units;
and trace metals in concentrations up to 1,000 mg/1 in incinerator scrubbers.
The efficacy of aerobic, anaerobic, and physical chemical treatment steps
on the wastestreams produced at incinerators, hydrapulping facilities,
pyrolysis units, and digesters is projected and potential treatment trains
are recommended.
INTRODUCTION
During the past ten years, shortages of basic raw materials such as ferrous
metals, scrap paper, and fuel oil have prompted private and governmental
agencies to investigate the recovery of valuable materials from solid wasres.
James M. Montgomery, Consulting Engineers, Inc.
S55 East Walnut Street, Pasadena, California 91101
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For example, the fuel shortage of late 1973 and the subsequent drastic
increase in fuel prices have resulted in a major effort to find alternative
sources of energy. One possible source of energy is the solid waste
generated from municipal, agricultural, and forestry operations. Although
the composition of these wastes varies widely with the type of enterprise,
consumer habits, geographical location, tiae of year, and numerous other
factors, the waste streams invariably contain a high organic content which
can be either directly combusted or converted to conventional fuels.
Without seme fora of recovery of their material and energy properties,
the increasing quantities of solid waste, along with projected depletion
of economical waste disposal sites, constitute a growing waste disposal
problem. Thus, the increased cost of fuel and raw materials coupled with
the increased concern over the environmental impact of disposing large
volumes of solid wastes, has prompted significant investigation into waste-
as-fuel CWAT) processes. This paper discusses one aspect of WAT processes:
the water pollutants produced and the technology available to treat these
wastes.
WASTIS7HEAM I3ENTITICATSCN
A two-step procedure is followed in processing refuse into useable fuel:
preprocessing and aonversion. Preprocessing consists of a series of
physical operations which size, classify, and segregate the raw refuse
into useable fractions. Conversion consists of cne of the follcving four
unit operations: conbusticn (mass incineration or co-firing), pyrolysis,
anaerobic digestion, or aethanaticn. From a water pollution control stand-
point, filtrate frcn hydrapulping (preprocessing), incinerator scrubber
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washwaters, pyrolysis condensate, centrate fran anaerobic digesters, and
leachate fran landfills (methanation) constitute the majcr sources of
wastewater.
The extent of water use and wastewater production axe primarily dependent
upon the type of process utilized for preparing the municipal solid waste
(MSW) and the actual combustion process itself. Wastewater streams range
from very small quantities of high organic deaand wastewater, such as that
associated with the condensate of pyrolysis units, to relatively large
volumes of low organic demand wastewater, such as that utilized to sluice
ash residue frca mass bum crmhustars. Four major catagories of pollutants
were identified in the wastestrearns at WRF facilities: the organic
surrogates (30D, COD, TSS), which measure the oxygen demand of the waste-
water on the receiving water body; the mineral quantity, specifically
corrosive agents such as chlorides and sulfates, and the hydrogen ion
concentration; the organic priority pollutants including total organic carbon
and total organic nitrogen; and the heavy metal priority pollutants. While
in most cases, good data were available on the organic surrogates and the
mineral quality of wastewater produced at refuse-derived-fuels (32F) and
WAF facilities, very little inforaation was available on the organic and
heavy metal priority pollutants.
PTS?K0CE3SING
The extent of wastewater production ir. preprocessing operations depends
almost exclusively on whether wet or dry preprocessing steps are utilized.
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In dry preprocessing operations, vastewatars axe produced in small quantities
at only a few locations. Water is used rarely in the actual process since
any moisture added to the RDF oust be eventually evaporated in the conver-
sion facility. The primary uses for water are dust control, fire fighting,
and clean-u? activities. Water is also used occasionally in some types of
material separation units, such as those recovering aluainum and glass.
Wastewaters primarily originate from washdcvn operations, drainage from
storage pits, and the above-mentioned materials recovery processes. Trash
confined in the storage pit may leach compounds such as pesticides and
organic solvents which can have adverse effects on wastewater treacnent,
but these conditions must be evaluated on an individual basis and treated
accordingly. In most cases the wastewater from dry preprocessing operations
can be discharged safely to sanitary sewers.
In contrast to dry preprocessing, wet preprocessing or pulping of MSV
involves placing the material into a large hydrapulper, analogous in
operation to a household garbage grinder. A thick slurry of MSW is formed
with heavy particles of ferrous materials and other ncn-farrous materials
separated by centrifugal action. The slurry containing the organic fraction,
glass, and small pieces of metal is segregated into light and heavy fractions
via licuid cyclone. The light organic fraction is dewatered by screening
and pressing, and the liquid waste streaa is recirculated to the pulper.
The dewatered pulp can be cleaned and dried for use in paper products or
burned for energy production.
Depending cr. the combination of energy recovery and materials separation,
203
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water is required for pulping, cleaning, equipment cooling, and resource
recovery. In most cases the quality of water is not critical, which permits
the use of non-potablS supplies such as sewage treataent plant effluents
and sludges. By far the largest quantity of water is required by the hydra-
pulper. Water far the hydrapulper can be obtained from the dewatering and
material recovery units through recirculation.
Three sources of wastewater exist in the hydrapulping system: the waste-
water blowdown from the recycling hydrapulping system, the sludge/slurry
mixture which has been dewatered in the cone press, and the effluent from
air pollution scrubbers. These wastewaters are characterized by their
large volume and high organic content. (Table 1.)
CONVERSION
Following preprocessing, the MSW is converted either directly into energy
or into fuels for combustion. Our study found wastewaters associated
with the two principal combustion processes; the mass burn incinerator and
the co-firing boiler; the anaerobic digestion process; and the pyrolysis
process. The latter two processes produce fuels for subsequent combustion.
The wastewaters from combustion processes consist primarily of site drainage
and washwaters; quench and sluice waters; boiler blowdown; and scrubber
effluent. The first three categories of wastewater are generally small in
quantity or of low strength and can be discharged directly into sanitary
sewers. The largest quantity of water is used for scrubbing exhaust gases.
Waterwall incinerator facilities help keep water use to a miris® by using
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electrostatic precipitators and dry handling systems for ash. While
electrostatic precipitators are preferred frcm a water pollution control
viewpoint, nevertheless wet scrubbers say be required for the removal of
gaseous chlorides and SO2 in order to meet air quality standards. The
scrubber waters are generally acidic, with pH's in the range 2.5 to 5.0.
The total solids concentration varies fraa 500 to 7000 mg/1 with about
80-85 percent being dissolved solids. The chloride, hardness, sulfate,
and phosphate concentrations of the inccoing raw water are significantly
increased after passing through the scrubber. Furthermore, the scrubber
wastewaters often contain high concentrations of trace metal priority
pollutants which must be reaoved prior to discharge to either the sanitary
sewer or the ambient receiving water. (Table 2.)
Pyrolysis involves heating a preprocessed to a sufficiently high tenper
tare in a low-oxygen environment so that the organic components breax down
chenicaliy. The heat for pyrolysis of MSw usually is obtained by totally
oxidizing part of the refuse. The pyrolysis reacticn produces.three com-
ponents : 1) a gas consisting primarily of hydrogen, methane, carbon mon-
oxide, and carbon dioxide; 2) an oily or liquid fraction which contains
organic chemicals such as acetic acid, acstone, and methanol plus water
derived from hydrolysis or organic compounds, and 3) a solid char fraction
consisting of unbumed carbon plus inert materials such as glass.
Water is used in pyrolysis plants for cooling, gas scrubbing, char quenchir.
and miscellaneous housekeeping. Wastewater straa-T.s of major concern are
those collected from scrubbers, condensers, and ether gas cleaning devices.
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These wastewaters usually are high strength and contain a variety of organic
materials formed during the pyrolytic reaction or vaporized from the raw
RDF. A BOD5 in the range 50,000 to 100,000 ppm is caused by water-soluable
organics such as alcohols, organic acids, and aldehydes. BOD's in this
range are too high for conventional activated sludge and nust be pretreated
by other processes. In addition to the high organic strength, the pyrolysis
condensate is characterized by high concentrations of organic priority
pollutants such as phenol, benzene, and toluene; and the gas scrubber waters
are characterized by high concentrations of trace metal priority pollutants.
(Table 3.)
Anaerobic digestion of sewage sludge to produce methane gas has been a
conanon practice in sewage treatment, however, anaerobic digestion of MSw
is only in the developmental stage at this time. A system for digesting
the organic part of municipal trash in a mixture with sewage sludge is
currently under shake down testing in Pompano Beach, Florida. Two waste-
water streams are anticipated: storage pit drainage and a liquid effluent
generated from dewatering the digested sludge. No data are available on
the composition of these waste streams when MSW is digested with the sewage
sludge. We anticipate that the dewatered filtrate from the digestion of
combined MSW/sewage sludge will be similar to that which exists at normal
sewage sludge digesters. Thus, the wastewaters will be characterized by
high BOD's, in the range 500-10,000 mg/1 and high concentrations of
organic priority pollutants, in the range of 650-3,800 mg/1. (Table 4.)
In sunmary, although many sources of wastewater exist at RDF and WAF
206
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facilities, the quantities and strengths of the wastewater are often small.
Consequently, these wastes can usually be discharged directly into the
sanitary sewer or held for a brief period in an -oxidation pond before
discharge to aobient receiving waters. In addition to these snail
insignificant scurcss, we found several major waste streans generated
in RDF/VAF facilities. The exact quantities and strengths of these
wastes are highly dependent upon the operating characteristics of the
particular facility, important constraints on operating characteristics
have been 1) the local air and water quality standards, and 2) the
availability of sanitary sewers.
The major waste streams of concern, associated with current 3DF/WAF
facilities, are:
1) Pressate from the devatared subsystem of the hydrapulping wet
preprocessing facility. This wastewater is characterized by moderate
SOD/COO (less than 10,000 ag/1), moderate suspended solids (less than
10,000 mg/1), and acidic pH (pH less than 7,0).
2) Pyrclysis condensates and gas scrubber effluents. These wastewaters
are characterized by very high (greater than 10,000 mg/1) 30D/C0D, low
(less than 1,000 mg/1) suspended solids, and high organic content,
especially phenols and benzene caapounds.
3) Filtrate and supernatant from anaerobic digesters. These wastewaters
are characterised by high (greater than 10,000 nc/1) 3GD/C0D, high
(greater than 10,000 ag/1) suspended solids, and neutral pH's.
4) Gas scrubber effluent frczi combustion facilities. These wastewaters
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are characterized by low (less than 1,000 mg/1) 30D/C0D, low (less than
1,000 mg/1) suspended solids, variable pH, and the presence of heavy
metals.
PROJECTED TREATMENT EFFICIENCIES
The efficiencies of pollution control technologies applicable to the
identified waste strezms are discussed in the following paragraphs.
As presented earlier, the principal waterborae emissions are the organic
surrogates (BOD, COD, TSS), the organic priority pollutants, and trace
metals. The first tvo are efficiently treated with biological processes,
either aerobic or anaerobic; whereas the latter are successfully removed
via physical-chemical processes. Physical-chemical methods are also
effective in removing organic surrogates but the total cost is higher
than with usual biological processes. Similarly, some adsorption ar.d
removal of trace metals occurs in biological processes, but this removal
is incidental to the real purpose: the conversion of soluble organic
material into microorganisms and gas.
Waste streams identified as quench water, sluice water, and ash pond
effluent associated with mass burn- and co-firing incinerators are readily
treated with existing control technology. Other waste streams such as
the scrubber waters at mass bum and incinerator facilities and digester
supematants at the anaerobic digester facilities appear amenable to
treatment via physical-chemical and aerobic biological processes,
respectively. Which of the tvo control processes would be most successful
in treating these wastes or whether the control processes may be required
in tandem should be investigated in pilot studies. The remaining two
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waste streams, the pyrclysis gas scrubber water and the thickner waste-
water from the hydrapulping process have far greater strength than
normally associated with domestic wastewater. ?ilot plar.t data (14-19)
indicate that these wastewaters should be amenable tc treatment by
anaerobic processes; the pyrolysis gas scrubber water being especially
adaptable to the anaerobic filter treatment process because of low
suspended solids and elevated temperatures, the hydrapulping wastewater
being amenable to the anaerobic biological contact process because of its
high suspended solids. Both of these treatment processes are in the
developmental stage and will require verification testing to determine
operating parameters and applicability to particular waste streams.
Aerobic biological processes can be applied effectively to any of the
organic pollutants identified earlier. Under aerobic conditions, the
soluble organic matter in a waste stream is converted into active
bicmass. Organic removal efficiencies of aerobic processes range betveen
80 and 90 percent. The removal efficiency of soluble organic material
from the liquid phase is actually greater; however, enough solids escape
the final clarification process to reduce the overall efficiency.
The efficiencies of the various treatment steps discussed above in removing
significant pollutants frca pertinent industrial discharges are presented
in Table 5. The listed industries produce wastestreams similar to those
encountered in T0F-WJJ" facilities.
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KECCKMENDED PILOT PLANT STUDIES
Based on the strengths of wastewaters produced at RDF-WAT facilities,
and the anticipated removal efficiencies of various treatrsent processes,
pilot plant studies are recommended to verify renoval efficiencies and to
determine whether linkage of processes in series is required to meet
discharge standards. The pilot plant studies would investigate the
effectiveness of aerobic, anaerobic, and physical-chemical processes
in obtaining the desired effluent quality.
Two main aerobic processes are available: filters and activated sludge.
In the biological filter, waste is applied continuously or intermittently
to the top surface of the filter. Natural rocks or ceranic or plastic
fill material have been successfully used as filter media. Air is
circulated through the filter either by natural convection or forced
draft to maintain aerobic conditions throughout the depth of the media.
A diverse population of microbites and microlutes live on the surface
of the media and utili2e the waste either directly or as high food chain
consumers.
In the activated sludge process, the microbial population is dispersed
in the liquid phase. The population is less diverse but more concentrated
than in a biological filter. Air is introduced into the liquid phase
to maintain aerobic conditions and to keep the microbial population in
suspension. Organic removal in activated sludge can be improved by
increasing the number of microorganisms in the mixed liquor or the period
of contact of the waste with the microorganisms.
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In order to provide flexibility in the operation of in aerobic pilot
plant, both the biofilter and the activated sludge processes should be
constructed. The biological filter can be selectively inserted into
the treatment train in front of the aeration tank. In addition to
overall increased efficiency, the diverse biota of the biological
filter are resistant to shock loadings and toxic elements, thus affording
a degree of protection against npset not available in an activated
sludge process alone. The effective depth of the biological filter can
be varied, as can the amount of flow path of recirculation within the
filter. Waste streams with high COD will probably require the use of a
biological filter as a first stage roughing filter prior to activated
sludge treataent.
The activated sludge aeration stage should be designed as a completely
mixed reactor; a configuration suitable for high organic loads and easy
operation. The aeration tank should be divisible into four ccnpartaents
to facilitate variation of aeration tiae. The aeration systea can be
converted froa air to pure oxygen.
Anaerobic treataent is well adapted to target waste streams containing
high concentrations of organic surrogates. An exception to the above
stateaer.t is the digester supernatant, where the efficacy of treating
the effluent froa an anaerobic treataer.t systea with another anaerobic
treataent systea is dubious.
The efficiency of anaerobic processes appears to increase with higher
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concentrations of organic surrogates and high temperatures in the anaerobic
reaction vessel. Thus, an anaerobic treatment process is ideally
suited for a vara, concentrated waste stream. The pyrolysis waste
is the primary candidate for anaerobic treatment because of its
concentration and elevated temperature. Another liJcely candidate is
the hydrapulping waste stream.
Based on the available data for waste streams at WAT facilities, two
anaerobic treanaent processes axe recoraended for construction in the
anaerobic pilot plant. These processes are the anaerobic filter and
the anaerobic contact chamber. In the anaerobic contact process, the
solids retention tiae is increased by recirculating sludge removed in
the secondary sedimentation tank. The anaerobic filter, on the other
hand, retains the sludge within the primary vessel; both on the media
and between the voids of the media. In anaerobic processes the
conversion of soluble organics to gases is high; eighty percent gas
(CJ4 + COj) to twenty percent sludge production is not uncommon. Because
of this, anaerobic processes can treat large quantities of organic waste
with only a moderate build up of sludge. Indeed, low sludge generation
and methane production are the two major advantages ef anaerobic treatment.
Operating experience with both types of anaerobic processes is scant.
Our literature review showed only one full-scale operation of the anaerobic
filter and no full scale operation of the anaerobic contact chamber. In
spite of these limited operations, both processes have significant
advantages over aerobic treatment. The anaerobic filter is simple to
operate, does net require sludge recirculation, and requires construction
of only one vessel.
71 7
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The physical-chemical treatment process is directly applicable to
the treatment of wastes found in incinerator scrubber waters. Furthermore,
the process aay be combined with either the aerobic or anaerobic
treatment processes to produce an effluent acceptable for discharge
to ambient receiving waters.
Since a physical-chemical pilot plant nay be used in a tertiary role as
veil as by Itself, the flow must be. ccmpatable with the other pilot
plants, particularly with the aerobic unit. Extensive bypass capability
oust be provided so that in the tertiary treatment mafe, individual unit
processes can be inserted or removed as desired. The unit processes of
flocculation, sedimentation, filtration, and carbcn adsorption should
be provided in the physical-chemical pilot plant.
Operational variables that can be controlled fcr experimental purposes are
1) the chemical dose—variation in amount and type of primary coagulant and
filter aid; 2) flocculation—flocculation energy input, detention time, and
sludge-solid content; 3} filtration—filter media design and filtration
rate; 4) carbon adsorption—contact time in the adsorption column.
OnliJce the biological units, the physical-chemical pilot plant does not
require a period of cell growth and acclamation upon startup. Most modifi-
cations to the treatment process can be accomplished in a matter of minutes.
Housing the physical-chemical processes in a separate trailer will provide
additional flexibility in the sequential or concurrent operation of the
different processes on the WAT waste streams.
Based on the waste streams generated in W\r facilities, ar.c the available
wastewater treatment processes and efficiencies, combinations of treatment
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processes nay be required to achieve the effluent limitations for discharge
to ambient receiving waters. In most cases, the use of a single treataer.t
process will produce an effluent acceptable for discharge to a publicly-
owned treatment wcrXs. However, in virtually all cases, a physical-
chemical process following either an anaerobic or aerobic process will be
required to polish the effluent and thereby meet discharge standards for
surface waters.
For hydrapulping waste streams, either anaerobic or aerobic processes
should be effective in producing a 90 percent reduction in the high BOD and
COD of these wastewaters. Tor comparison purposes, two anaerobic processes,
the anaerobic filter and the anaerobic contact chamber will be operated
•v
in parallel along with the aerobic pilot plant, consisting of a roughing
filter and activated sludge aeration. Based on the efficiencies of these
processes, the effluent should be acceptable for discharge to POTW. For
discharge to surface waters, a physical-chemical pilot plant must be
utilized to further reduce both organic and inorganic contaminants.
(Figure 1.)
For contaminants identified as occurring in incinerator or boiler scrubber
waters, either aerobic or physical-chenical processes should be effective
in treating the relatively low BOD waste streams. The physical-chemical
pilot plant should effectively reduce both the organic contaminants ar.d the
trace metal concentrations to levels acceptable for discharge to surface
waters. The aerobic treatment process will probably require subsequent
polishing via physical-chemical processes to remove trace metal contaminates
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to levels acceptable for discharge to surface waters.
The waste screams produced in the condensation of cases and the
•separation of pyrolysis fuel oils from the scrubber ail are the most
difficult to treat. Based on the very high 300's and the low suspended
solids iron this WAF process, the anaerobic filter appears ideally
suited for the initial treatment step. To date, the anaerobic filter
has been utilised only ones in full scale operations and consequently
the pilot plant data vill be especially valuable in the development of
this innovative technology. The anaerobic contact process will run
concurrently with the anaerobic filter for comparison between the two
processes. Likewise, the aerobic pilot plant should be utilized with the
pyrolysis waste streams and the results compared with those frco the OHOX
process utilised by the Onion Carbide Company in treating their Purox
wastewaters. Subsequent physical-chemical treatment may be required
prior to discharge to surface waters for the removal of traca metals
although these have not been specifically identified in the analysis of
pyrolysis waste streams, (Figure 3.)
The wastewaters from the anaerobic digestion of MSW are the most poorly
characterized because the process itself is only now undergoing full
scale investigation. Depending on the oxygen demand of the waste streams,
either the aerobic or the physical-chemical processes should be effective
in its treatoient. The aerobic process would generally be ineffective
in the removal of trace metals and consequently, based on results of
further testing, a physical-chemical process may be required to upgrade
the effluent. (Figure
-------
In conclusion, based on the results of our investigation, we feel that
three pilot plant trailers should be designed, constructed, and
operated in the field at WAF facilities. These three pilot plants,
anaerobic, aerobic and physical-chemical, should be operated both
in series and in parallel to obtain data on the relative efficiencies
of the different processes. The operation of the anaerobic pilot plant
should be especially valuable because of the innovative nature cf the
processes involved. In addition, the operation of the other pilot plants
will provide valuable information on their respective removal efficiencies
with respect to organic and trace metal priority pollutants. The
successful operation of the pilot plants at WAF facilities will provide
valuable information on the wastewater streams generated and the
applicability of various treatment schemes in reducing the pollutant levels
in these waste streams to acceptable levels.
acknowledgement
This study to characterize liquid pollutants produced at PDF-WAF facilities
and to recc-nsnend treatment steps for their removal was funded by the
Fuels Technology Branch, Industrial Environmental Research Laboratory,
Environmental Protection Agency, Cincinnati, Chio.
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TABLZ 1
SOMMAICf OF SIGNIFICANT POLLUTANTS IDENTITIZD IN SYT5RAPTJL?XKG KASTZ STSSAKS [i]
?A?jy
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TABLE 2
SUMMARY OF SIGNIFICANT POLLUTANTS IDENTIFIED IN INCINERATOR WASTE STREAMS [2-3]
PARAMETER (nq/13
QUENCH WATER
SCRUBBER WATER
Organic Surrogates
3.O.D.
-*
15-400
C.O.D.
•
20-790
T.S.S.
4-4,070
90-13,000
Oil and Grease
•
•
Mineral Quality
+
Na
ca+2
3.36-1,306
14-1,621
66-517
19-1,4 99
Total Alkalinity
0-835
0-2,630
CL
98-1,920
180-3,540
S042
25-5000
20-1,250
^3
P°4
35-100
1-21
10-710
1-51 '
CN
•
5.2
pH (Units)
3.6-11.5
1.8-11.9
DO
*
*
Priority Pollutants
Organics
«
*
Priority Pollutants
Metals
*
Hg
AS
0.03-11
0.2-7
T-C
ft
1-200
Cr
0.06-7
Pb
13-500
Cd
1.2-20
Fe
40-3,600
Cu
1-52
Zn
30-1,050
Mn
£-65
' Flow (liter/sin)
Corcinec
flows up
to
2,000 1/m
218
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TABLE 3
SXSWfUCf OF SIGNIFICANT POLLUTANTS IDOTI7IZD H7 PYHOLYSIS WASTE STREAMS [9-11]
PA2A>ETSH (bc/IJ
PY5CLYSIS COTOEMSATE and GAS SCH033ES WATE3
Organic Surrogates
B. 0. D.
50,000-77,000
C.O.D.
30,000-52,000
T.S.S.
30-112
Oil and Grease
500-1,000
Mineral Quality
Na+
89-170+
Ca+2
34-135+
Total Alkalinity
CL~
360-€90+
S0I2
44-€2+
N°3
«
TO43
*
CM
2-a+
pH ( units )
3.7+
CO
2.4-3.7+
Priority Pollutants
Qrgaaics
Phenol 20-50+
2-4 Diaethyl ?hcno 0.6-5+
Benzene 4+
TOluene 1+
Ethylbenaene 1+
Naphthalene 3+
Priority Pollutants
Metals
Lead 0.3-0.S+
Zinc 2.3-15+
Flow (litar/nin]
Op to 250-reports differ
219
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TABLE 4
SUMMARY OF SIGNIFICANT POLLUTANTS IDENTIFIED
IN DIGESTER SUPERNATANT/FILTRATE [12-13]
PARAMETER (mc/1)
DIGESTER SUPERNATANT/FILTRATE
Organic Surrogates
B.O.D
500-10,000
C.O.D.
1,000-30,000
T.S.S.
200-15,000
Oil and Grease
«
Mineral Quality
+
Na
•
^ +2
Ca
*
Ttotal Alkalinity
100-2,700
CL
•
SC42
*
N°3
«
?°43
•
cn"
*
pH Cur-its)
6.4-7.2
DO
*
Priority Pollutants
Organics
TOtal .volatile solids 650-3,300
Priority Pollutants
Metals
*
Flow (liter/i&in]
•
220
-------
TABLE 5
efficiency gf treats;? processes in removing significant
POLLUTANTS FROM PERTINENT INDUSTRIAL DISCHARGES (20-22)
Percent Removal (\)
Indus try/Le ve 1
or TTeataent
BOD
COD
35
Oil i
Grease
Phenol
Aitsnonia
Sulfide
Metals 1
Pe trol s'ja.
Prxnary
3iological
Secondary
Filtration
Carbon Adsorption
Anaerobic Filter
30-60
40-99
40-70
70-98
20-50
30-95
20-53
70-94
10-13
50-30
20-85
75-95
60-90
60-95
50-99
65—95
70-95
0-50
60-99
5-20
90-100
0-99
70-100
Stean Electric
Power
Primary
Biological
Secondary
Anaerobic Filter
50-70
70-90
50-95 |
Puis S Paoer
Primary
Biological
Secondary
Anaerobic Filter
8S-99
73-94
95
Staan Supply a
Cooline
Precipitation &
Coagulation
90-100 1
Organic Cienicals
3iological
Secondary
Carbon Adsorption
93
90
69-74
69
Plastics s
Synthetics
Biological
Secondary
30-99
90-95
1
Food Processir.c
Anaerobic Filter
55-56
1
Pharmaceutical
Anaerobic Filter
94-98
1
Wastewater Treat-
ment Plant
Anaerobic Filter
85
76
45
1
i
221
-------
REFERENCES CITED
1. Ywong, J. C., and Johnson L., "Water Use and Wastewater Production
at Solid Waste Processing/Energy Recovery Facilities," Engineering
Research Institute, Icwa State University, Ames, Iowa, 1977.
2. Matusky, F. E., and Hampton, R. K., "Incinerator Wastewater,"
Proceedings National Incinerator Conference, 1968.
3. Achiger, W. C., and Daniels, L. E., "An Evaluation of Seven
Incinerators," Proceedings National Incinerator Conference, 1970.
4. Wilson, D. A-, and Brown, R. E. , "Characterization of Several
Incinerator Process Waters," Proceedings National Incinerator
Conference, 1970.
5. Schoenberger, R. J., et al, "Characterization and Treatment of
Incinerator Process Waters," Proceedings National Incinerator
Conference, 1970.
6. Schoenberger» R. J.» "Studies of Incinerator Operation," Proceedings
National Incinerator Conference, 1972.
7. Cross, F. L., and Ross, R. W., "Effluent Water From Incinerator Flue
Gas Scrubbers," Proceedings National Incinerator Conference, 1963.
8. Kaiser, E. R., and Carotti, "Municipal Incineration of Refuse with
2 Percent and 4 Percent Additions of Form Plastics: Polyethylene,
Polyurethane, Polystyrene, and Polyvinyl Chloride, "Proceedings
National Incinerator Conference, 1972.
9. Engineering and Economic Analysis of Waste to Energy Systems, Ralph
M. Parsons Company report to EPA Industrial Environmental Research
Laboratory, June 1977.
10. Hoffman, D. A., Pyrolysis of Solid Municipal Wastes, EPA report
67012-73-039, Cincinnati, Ohio, 1977.
11. Ananth, C. et al, Environmental Assessment of Waste-to-Energy Process:
Union Carbide Purex System, MKI report to EPA Industrial Environmental
Research Laboratory, June 1978.
12. Malina, J. F., and Felipo, J. D., "Treatment of Supernatants and
Liquids Associated with Sludge Treatment," Water and Sewace wcrfcs
Journal, August 1971.
13. Sludge Treatment and Disposal, EPA Technology Transfer Manual, 1974.
14. Jennett, J. and Dennis, D., "Anaerobic Filter Treatment of Pharmaceutical
Waste," Journal Water Pollution Control Federation, 47,l(January 1975).
15. Young, J. C., and McCarty, p. L., "The Anaerobic Filter for Waste
Treatment," Journal Water Pollution Control Federation, 41, 5 (May 1969).
222
-------
16. Taylor, W., Full-Scale Anaerobic Trickling Filter Evaluation, Food
Waste Research Section, US EPA, Cincinnati, Ohio.
17. Sana, R. T. , Raksit, S. K. , and Wong, G. G., "Anaerobic Filter Treated
Waste Activated Sludge" Water and Sewace Works Journal, 124, 2
(February 1977). '
18. Sanders, F. A., and Bloodgocd, D. E., "The Effects of Nitrogen-to-
Carbon Ratio on Anaerobic Decomposition," Journal Water Pollution
Control Federation, 37, 12 (December 196S).
19. Schoepfer, G. J,, and Zeiake, N. R., "Development of the Anaerobic
Contact Process, I, Pilot Plant Investigation and Economics," Savage
and Industrial Wastes, 31, 2 (February 1959).
20. State and Local Pretreataent Programs, Federal Guidelines. Volume I,
US OA, Municipal Construction Division, Washington, D.C. January 1977.
21. State and Local Pretrsatment Pro
-------
HYORAPVUPtNfi WASTESTOCAM
r
ANACTOBJC
. FILTER
ANACRO0IC
v 03NTACT
SCSIMO(TAT)OH
SCOtMeXTATION
PR1MAPV
tNTXRMCaAT£
CLAfllFIER
CFFLUCNT
TO POTW
EFFLuCnT
TO POTW
TO WTW
n^CCJLATO*
DUAL wEDIA |
P1LTOTS | }
1
' 1
CAR30N AOSORPTIOnI |
COLUMNS | j
^1
PHYSIOL
CHEMICAL
PILOT
PLANT
effluent to
SURFACE WATERS
AEROBIC AND ANEROBIC TREATMENT PROCESSES,
FOLLOWED 3Y PHYSICAL CHEMICAL TREATMENT
SHOULD 3E INVESTIGATED IN THE TREATMENT
OF HYDRAPULPING WASTESTREAMS (TABLE 1)
Figure 1
224
-------
scauaaca watg?
EFTUJENT
TO POT*
PRIMARY
G-AWIflEf?
EFFLUENT TO
SECONQARY
vC-ARIFIEH .
CARSON
ABSORPTION
C3UJMN3
FLOCCUOTOR
FLOCCULATCR
OVJAU. MEDIA
FILTERS
ACTIVATED
SLUOGE
CARSON
AOSORPT1CN
COLUMNS
CXJAi_ MEDIA
FILTERS
SURFACE WATERS
BOTH AEROBIC AND PHYSICAL CHEMICAL TREATMENT PROCESSES
SHOULD 3E INVESTIGATED IN THE TREATMENT OF
SC5U3BER WATERS (Table 2)
Figure 2
-------
rrmxrsis •a*te5T*cw*
i
AHA£POQlC
. CONTACT,
SCC* MOT A TUX
IC0IMO4TATIOM
1MTCRM tD» + TZ
ri AOinra f
m ruiMCDiAre
Voffline* V
njCOJLATOB
CAM BON AOSOftPTION
OUJMKS
crn-ucwT to
su*FACt «ATors
AEROBIC AND ANAEROBIC TREATMENT PROCESSES, OPERATED
IN SERIES AND IN PARALLEL, SKCCJLD 3E INVESTIGATED
IN THE TREATMENT OF PYROLYSIS WASTESTREAMS (Table 3)
Figure 3
226
-------
OU3C3TOI m.7*ATE
AOIOfflC
*UOT
ruant
PRIMARY
PRIMARY
cu#ir\a*
04fiX4lCAl
OUAi. MCStA
HUTS?
intepm court
O^ARtHS?
GAR80* A ~SORPTION
CSCUMNS
ETFUUCNT TO
SURFACT WATOW
PUW4T
OJAC MQIA
OUTERS
CARSON aosor*tioh
COUJMNS
CFFUJClT TO 3URFACZ WATERS
AEROBIC AND PHYSICAL CHEMICAL TREATMENT PROCESSES
SHOULD 3E INVESTIGATED IN THE TREATMENT
OF DIGESTER WASTESTREAMS (Table 4)
Ficiire 4
227
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completingj
I.SEPORTNO. 2.
3. RECIPIENT'S ACCESSlOl^NO.
a. title amo subtitle
Proceedings from a Technical Conference on
Waste-Co-Energy Technology Update - 1980
5. REPORT DATE
September, 1980
6. PERFORMING ORGANIZATION COOE
G-8290
7. AUTHOR(S)
G. Ray Smithson, Jr.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME ANO AOORESS
Battelle Columbus Division
505 King Avenue
Columbus, Ohio 4 3201
10. PROGRAM ELEMENT NO.
11. CONTRACT/GHANT no.
R 806 653 010
12. SPONSORING AGENCY NAME AND AOORESS
Incineration Research Branch
Industrial Pollution Control Division
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT ANO PERIOD COVERED
Proceedings
14. SPONSORING AGENCY COOE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The Technical Conference on Waste-to-Energy Technology Opdate-1980 was held ac
Cincinnati, Ohio, on April 51 and 16, 1980. The purposes of the technical conference
were:
o To review the status of relevant research and
development activities being supported by U.S.
EPA's Industrial Environmental Research Laboratory
at Cincinnati, Ohio.
o To consider the most effective means for the
commercial exploitation of the results of this
research.
o To review areas for future research and to recommend
strategies for the implementation of such research.
The conference was presented in three technical sessions; these are Conversion
Processes, Combustion, and Environmental Assessments and Pollution Control Technology
These proceedings incorporate copies of the papers presented by the conference
speakers.
17. KEY WORDS ANO DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATi Field/Group
Was te-to-Energy
RDF
DRDF
Energy Recovery
Waste Disposal
i3. DISTRIBUTION STATEMENT
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO.PAGES
20. SECURITY CLASS (This page)
11. PRICE
EPA Form 2220-1 (9-73)
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