BALTIMORE
DEMONSTRATES
GAS PYROLYSiS
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BALTIMORE
DEMONSTRATES
GAS PYROLY5IS
resource recovery
from solid waste
This first interim report (SW- 75d. i) on work performed under
Federal solid waste management demonstration grant No. S-801533
to the City of Baltimore was written by DAVID B. SUSSMAN.
U.S. ENVIRONMENTAL PROTECTION AGENCY
1975
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An environmental protection publication (SW-75d.ij
in the solid waste management series
Mention of commercial products or organizations does not constitute
endorsement by the U.S. Government
For sale by the Superintendent of Documents, U.S. Government Printing Office,
Washington, D.C. 20402
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foreword
The solid waste generated each year by urban areas in the United States
contains an estimated 830 trillion Btu of energy—the equivalent of 400,000
barrels of oil per day, which is nearly a third of the Alaskan pipeline's pro-
jected flow. In addition to energy, 7 percent of the iron, 8 percent of the tin,
and 14 percent of the paper consumed each year could be supplied from what
is now waste. At present, despite concern about shortages of energy and
materials, less than 1 percent of the resources in municipal waste is being re-
claimed; the rest goes into dumps, landfills, and incinerators.
Large-scale recovery of usable waste materials would not only conserve re-
sources but also save the environment from much of the pollution, hazards to
health, and blight caused by improper disposal. The increasingly burdensome
cost of disposal in urban areas is another reason to urge reuse. And informa-
tion is emerging to show that recycling has other benefits that are not so ap-
parent. When two production systems are compared, one using virgin mate-
rials, the other waste materials, the system using wastes almost always causes
less air and water pollution, generates less solid waste, and consumes less
energy. These differences appear when the environmental impacts of all
activities are measured—mining, processing, fabricating, manufacturing, and
the transportation and disposal steps in between.
The Nation's task, then, is to mobilize our systems and institutions to-
ward recovering and using the resources in waste. One tool that should facil-
itate that movement is new technology. But technological advances are usual-
ly expensive and entail risk. The Resource Recovery Act of 1970 (which
amended the Solid Waste Disposal Act of 1965) enabled the Federal solid
waste management program to assist States and municipalities by assuming
part of the risk of trying new technologies. The result was a significant ex-
pansion of the Federal resource recovery demonstration program. This report
describes one project in that program, in which energy will be recovered in
the form of steam by converting solid waste into a combustible gas through
pyrolysis and then using the gas as a fuel to fire a steam boiler. Ferrous
metals will be recovered from the pyrolysis residue, as well as a glassy aggre-
gate for use in street construction and a carbon char that has possible uses in
wastewater treatment and soil conditioning.
The process was developed on a pilot scale by Monsanto Enviro-Chem
Systems, Inc., St. Louis, Missouri. In July 1972, the City of Baltimore
applied to the U.S. Environmental Protection Agency for a grant to demon-
strate this Monsanto "Landgard" system with a full-scale pyrolysis plant that
ill
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would process about half of the city's solid waste. The grant that was
awarded covers 40 percent of the cost of the project. Construction began in
early 1973 and operation is scheduled to begin in early 1975.
The Baltimore project will recover energy and materials from waste, relieve
the city's disposal problem, and have beneficial effects on the environment.
The projected costs and revenues indicate a good possibility that the plant
can do all this at a cost competitive with or lower than that of landfilling or
incineration.
This demonstration exemplifies the kind of creative solutions that gov-
ernment at all levels, industry, and the public must pursue to bring our
environmental and resource conservation problems under control.
-ARSEN J. DARNAY
Deputy Assistant Administrator
for Solid Waste Management
IV
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BALTIMORE
DEMONSTRATES
GAS PYROLY5IS
resource recovery
from solid waste
ALTHOUGH a number of European countries have been generating steam
and electricity from municipal solid waste for years, recovery of energy from
municipal solid waste has been limited in the United States. Until recently, it
consisted of relatively inefficient waste-heat boilers installed in conventional
incinerators. In the past 5 years, however, more sophisticated solid waste
incinerators have been built which incorporate boilers for the recovery of
steam. But these newer facilities, known as waterwall incinerators, have
several important limitations. First, the ability of these incinerators to meet
and maintain clean air standards economically is questionable. Pollution
control of incinerators is expensive and technically difficult. Second, the new
facilities are relatively expensive both in capital and operating cost. Third,
their relative reliability has not always been acceptable. Fourth, the energy
conversion efficiency is somewhat less than desirable.
By converting solid waste into a new fuel and burning the fuel in a boiler,
the above limitations can be reduced. While the pyrolytic conversion of solid
waste into steam is not a panacea for either the solid waste problem or the
energy crunch, it certainly can be a significant part of the solution to both.
The concept was considered attractive enough for the City of Baltimore to
undertake a demonstration with financial support from the U.S. Environmen-
tal Protection Agency's Office of Solid Waste Management Programs. The
project is scheduled to begin processing waste in early 1975.
Objectives
The primary objective of the project is to demonstrate the technical and
economical feasibility of recovering energy from mixed municipal waste using
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a gaseous pyrolysis process. (Pyrolysis is the physical and chemical decompo-
sition of organic matter brought about by the action of heat in an oxygen-
deficient atmosphere.) The City of Baltimore is building a full-size, 1,000-ton-
per-day plant that will receive mixed municipal solid waste, including krge
household appliances and tires. Sewage sludge may also be included. The
Baltimore plant will generate steam, recover ferrous metals, and produce char
and a glassy aggregate product. The project includes the design, construction,
operation, and evaluation of a system that will convert most of the incoming
waste into usable products in ways that will meet all pollution control
standards. Approximately half of Baltimore's residential solid waste will be
processed by this plant.
The~project also will evaluate the marketing of steam, ferrous metals, and
pyrolysis residues.
Benefits
The project has many potential benefits. The most important ones are:
(1) the disposal of about half of the city's residential solid waste without
environmental degradation, (2) the energy recovered from the waste in the
form of steam and the associated saving of fossil fuels, and (3) a disposal cost
that is less than that of landfilling and incineration, according to a pre-
liminary economic analysis.
Participants
EPA awarded $6 million toward the cost of the $16 million project. The
Federal share was provided under the authority of Section 208 of the Solid
Waste Disposal Act, as amended.
The Maryland Environmental Service (MES) provided the project with a
$4 million loan. MES is an agency of the State Department of Natural
Resources and has authority to finance projects that preserve, improve, or
manage the State's air, water, and land resources.
The City of Baltimore is providing the remaining $6 million for the
pyrolysis plant, and the land on which the plant is sited. The loan from MES
will be reimbursed from the proceeds received from the sale of the steam,
glassy aggregate, and ferrous metal.
Monsanto Enviro-Chem Systems, Inc., of St. Louis developed the
"Landgard"* system and operated a 35-ton-per-day pilot plant. Monsanto
also designed and, through their subsidiary, the Leonard Construction Com-
*Landgard is a proprietary system; apparatus and process patents have been allowed
by the U.S. Patent Office.
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1. RECEIVING
2. SHREDDERS
3. STORAGE
4. REACTOR
5. AFTERBURNER
6. BOILERS 11. CARBON CHAR
7. SCRUBBER 12. FERROUS METAL
8. PLUME SUPPRESSOR 13. STEAM LINE
9. RESIDUE SEPARATOR
10. GLASSY AGGREGATE
Figure 1. Artist's sketch of the Baltimore plant.
pany, is building the 1,000-ton-per-day plant in Baltimore. Monsanto will
turn over to the city a fully operational, demonstrated plant early in 1975.
Schedule
Construction is presently underway. All development and pilot testing
work has been completed by Monsanto. The major dates on the project
schedule are:
Groundbreaking
Complete design
Complete construction
Plant start-up
Operation and evaluation
January 1973
January 1974
December 1974
January to March 1975
April 1975 to April 1976
Although it is expected that the plant will operate as planned, the reader
should be aware that the data presented in this report are based on the
experiences of the 35-ton-per-day pilot plant. The economic estimates and
recovery rates are projected from those data.
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system description
Original Development Work
In 1967 Monsanto began a survey of solid waste problems and their future
impact. The company, because of long experience in materials processing,
decided to concentrate on disposal methods and investigated various ideas,
including pyrolysis. They perceived resource recovery as an attractive tool in
solid waste management and pyrolysis as the most attractive option. A study
of pyrolysis processing systems determined that direct-fire pyrolysis using a
rotary kiln would be the best method. A rotary kiln is a cylindrical chamber,
slightly inclined, that rotates about its horizontal or lengthwise axis. Solid
waste enters the high end of the kiln. Fuel is fired directly into the kiln
(hence, the term direct-fired) rather than burned to heat the kiln's outer
shell as with a popcorn popper. Rotation tumbles the material and allows for
complete heating. Gravity slowly moves the material to the low end for dis-
charge. Rotary kilns are used extensively in the cement industry and in pro-
cessing many granulated materials. Monsanto has designed and operated
several similar units.
After a laboratory model of a direct-fire continuous pyrolysis unit was
built and operated in Dayton, Ohio, Monsanto decided to build a pilot-size
pyrolysis unit near St. Louis to develop scale-up data for designing a full-size
plant. Trial handling of mixed municipal solid waste began in June 1969.
GAS
SCRUBBER
STEAM /
RECEIVING
CLEAN AIR TO
ATMOSPHERE
I
STAC
FAN
WATER CLARIFIER
RESIDL
MAGNET
WATER
QUENCHING -9-
FERROUS
METAL
Figure 2. The processing at the Baltimore plant is depicted in this flow
diagram.
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Continuous operation at a feed rate of 35 tons per day was demonstrated
by early 1970. The next year, a system was added to recover carbon char,
glassy aggregate, and ferrous metal from the residue. The pilot plant was dis-
mantled in late 1971 after all testing was completed.
The system being built in Baltimore is a scale-up to 1,000 tons per day
from the 35-ton pilot plant. Scale-ups of this ratio are common in both the
petrochemical and materials processing industries, and no major scale-up
problems are expected.
The Site
The plant is located on a 16-acre peninsula just south of the Baltimore
business district. The entire site is zoned industrial, and its use for the pyrol-
ysis plant is consistent with industrial redevelopment plans for the area.
Waste Types Processed
The plant will accept residential and commercial solid waste typical of
U.S. cities (Table 1). Large household appliances, occasional tires, and the
like will be processed; however, automobiles and industrial wastes are ex-
cluded. The ability of the plant to accept bulky items is a function of the
shredder size and design, not of the pyrolytic process. Oversized or non-
shreddable waste can be removed from the system before processing by the
loader operators. Automatic safety devices will remove large, nonshreddable
wastes or stop the conveyor belt, thereby preventing damage to the processing
equipment.
Sewage sludge was pyrolyzed successfully at the pilot plant; this practice
may be further demonstrated in the Baltimore project.
Capacity
The receiving and shredding system is designed to process 1,000 tons of
solid waste during a 10-hour daily shift. The pyrolysis reactor, materials
recovery, and steam generator subsystems will operate continuously 24 hours
per day, 7 days per week. In order to feed the reactor continuously from the
intermittent preparation stream, a storage bin with a capacity of 2,000 tons is
provided.
Receiving Area
Raw solid waste is discharged from conventional collection vehicles into a
concrete pit in the receiving building. The collection trucks are weighed
prior to and after dumping for purposes of billing and determining the ton-
nage processed. Two bulldozers push the dumped waste onto two separate
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TABLE 1
Composition of Municipal Solid Waste4
Kind of material
Percent of incoming waste
Paper
Glass
Metals
Ferrous
Aluminum
Other
Plastics
Rubber and leather
Textiles
Wood
Food wastes
Yard wastes
Miscellaneous inorganics
8
It
It
38
10
10t
4
3
2
4
14
14
1
100
Chemical analysis
Proximate analysis
(pre-pyrolysis)
Ultimate analysis
(post-pyrolysis)
Component
Moisture
Volatiles
Fixed carbon
Inerts
Percent
21
45
8
26
100
Component Percent
Ferrous 7
Glass and ash 19
Water 21
Carbon 25
Sulfur and nitrogen It
Hydrogen 3
Oxygen 24
100
*Sources: Percentages of kinds of materials are from EPA study of typical composi-
tion of U.S. municipal solid waste streams. The chemical analysis is based on samples
taken at the Monsanto pilot plant in St. Louis.
fLess than percent shown.
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conveyors that lead to the shredders. The conveyors are located at opposite
ends of the receiving pit and elevate the waste from below floor level in the
pit to the top of the shredders. The receiving pit is 160 feet long, 80 feet
wide, and 14.5 feet deep, and will hold 1,000 tons of refuse at a density of
270 pounds per cubic yard.
Shredders
Mixed municipal solid waste is very heterogeneous. Most materials-conver-
sion processes require a reasonably homogeneous feed, however. Shredding
the waste homogenizes it, reduces odors, and makes handling easier. Each of
the two hammermill shredders at the Baltimore plant contains 30 large ham-
mers that swing on pins attached to a horizontal shaft. They grind or mill the
waste against steel grates until the particles are small enough (4-inch diameter)
to fall through the grates. The milled refuse falls onto a conveyor that trans-
ports it to the storage bin or directly to the kiln.
The shredders are manufactured by Jeffrey Manufacturing Company,
Columbus, Ohio. Each has a rotor (shaft, pins, and hammers) that is
73 inches in diameter and 99 inches long, and is belt-driven by a 900-horse-
power electric motor.
Storage Bin and Reactor Feed
Shredded municipal solid waste is difficult to store. It is conveyed easily,
but once piled up, it tends to stick together and become dense. A conical,
live-bottom, Atlas storage bin with a 2,000-ton capacity was chosen to store
the shredded waste. This device was originally developed for agricultural
products but handles solid waste well. A similar storage bin has been used
successfully at another EPA-supported energy recovery project, located in St.
Louis.
The shredded waste enters the top of the bin and forms a conical pile. A
rotating drag line with buckets at the bottom of the pile undercuts the pile
and drags the material to a conveyor under the floor of the bin. The storage
bin effectively isolates the dumping, loading, and shredding operations from
the downstream processes; it acts as a buffer to absorb minor process inter-
ruptions so that the waste can be fired continuously into the pyrolytic
reactor (kiln).
The shredded waste is conveyed from the storage bin at a constant rate and
fed into the reactor by twin hydraulic rams.
Pyrolytic Reactor
The pyrolysis reaction takes place in a refractory-lined horizontal rotary
kiln with a throughput of 42 tons per hour. The kiln is 19 feet in diameter,
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Figure 3. The pipeline will transport steam, the plant's major product, to Balti-
more Gas & Electric's steam distribution line. The structure at center of photo houses
100 feet long, and rotates at approximately 2 revolutions per minute.
The concrete-like refractory lining keeps the heat of reaction within the
kiln and prevents erosion of the kiln shell. The heat required to accomplish
the pyrolysis reaction is provided by both the partial burning of the solid
waste and a supplemental fuel. A portion of the solid waste is combusted
using 40 percent of the air theoretically required for complete combustion.
No. 2 heating oil, at the rate of 7.1 gallons per ton of waste, provides the re-
mainder of the required heat. The fuel oil burner is located in the discharge
end of the kiln. Pyrolysis gases move counter-current to the waste and exit
the kiln at the feed end. The gas temperature is controlled to 1,200 F and the
residue is kept below 2,000 F to prevent slagging. If the temperature of the
residue goes above 2,000 F, the glass particles will melt and stick to the metal,
and all the residue would become one dense mass that would require crushing
for further processing.
Energy Recovery
The pyrolytic gases leave the kiln and go to the afterburner (gas purifier)
where they are combusted with additional air. The gases, which have a heat
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the rams for feeding the shredded waste into the kiln as it is conveyed from the storage
bin.
content of about 120 British thermal units (Btu) per dry standard cubic foot,
consist of the following:
Nitrogen
Carbon dioxide
Carbon monoxide
Hydrogen
Methane
Ethylene
Oxygen
Percent by volume, dry basis
69.3
11.4
6.6
6.6
2.8
1.7
1.6
The combustion temperature is in the range of 1,400 F to assure efficient and
complete burning. The heat released from burning the gases is directed into
two waste-heat boilers (heat exchangers), operating in parallel, which generate
200,000 pounds of steam per hour.
Exhaust Gas System
After exiting the boilers, the waste gases are cleaned of particulate matter
in a water spray unit called a scrubber. The scrubbed gases then pass through
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an induced draft fan which provides the force for drawing the gases through
the entire system. The gases, saturated with moisture, are passed through a
dehumidifier where they are cooled (by ambient air). The water thus re-
moved is recycled. The dehumidified, cooled gases are then combined with
ambient air that has been heated and discharged to the atmosphere. This
process suppresses the formation of steam plumes.
Solids are removed from the scrubber water system by diverting part of
the recirculated water to a thickener, a tank where the solid material is
allowed to settle out. Flocculent (chemicals that cause the suspended solids
to lump together and settle quickly) is added in the thickener to aid in solids
removal. The clarified thickener overflow is recycled to the scrubber while
the underflow stream containing the settled solids is used as coolant in the
residue quench tank. The cooler-scrubber water system is a closed loop re-
quiring very little makeup water. The plant is designed to allow the after-
burner gases to bypass either or both of the boilers and enter the scrubbing
tower directly. This feature allows the plant to dispose of solid waste during
boiler outages or at times when the demand for steam is low.
Materials Recovery
The hot residue is discharged from the kiln into a water-filled quench tank.
A conveyor dewaters the wet residue and elevates it from the quench tank
into a flotation separator. A light material, carbon char, floats off as a slurry
and is thickened and filtered to remove the water. Clarified water and filtrate
are recirculated within the plant's closed-loop water system. The wet (50 per-
cent moisture) carbon char will be disposed of in a land disposal site until
firm markets for the material are developed (see section on The Products and
Their Marketing). The remaining heavy material (sink fraction) from the bot-
tom of the flotation separator is conveyed to a magnetic separator where the
ferrous metals are removed and deposited into containers for shipment to a
scrap user. The balance of the heavy material is about 65 percent glass. This
material, called glassy aggregate, is passed through screens with Vi-inch open-
ings and then stored on-site. This glassy material will be used as aggregate in
the bituminous concrete product (often called "glassphalt") used to pave the
city's streets.
Figure 4. The large structure in the foreground is the scrubber for cleaning the
waste gases coming out of the boilers.
Figure 5. The residue from the pyrolysis reaction is conveyed to building at
left, where materials recovery processing begins.
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Redundancy
Since waste generation will continue whether the processing plant is able
to operate or not, a standby disposal system or redundant processing line is
required. For short periods of system downtime, the 3-day storage capacity
of the dump pit and storage bin will be put to use. The plant is designed with
a quick repair capability. There are many installed spares, and changeover
will take minimum time. All equipment is designed to be repairable or re-
buildable within 3 to 5 days. Even the kiln's refractory lining could be re-
placed within this short downtime. The two waste shredders are operated in
parallel, each with the capacity of 50 tons per hour. Since they operate inde-
pendently, either could feed the plant by itself, at a lesser throughput or
over a longer shift.
Figure 6. The Baltimore plant's energy and material balances have been esti-
mated. In energy efficiency this plant is expected to compare well with other types of
utility plants.
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Energy Balance
As with any energy system, the energy balance sheet is of prime impor-
tance in determining overall system efficiency and effectiveness. A solid
waste disposal system can be either energy consumptive, neutral, or energy
producing, depending on its design and technology. In choosing pyrolysis as a
technology, a net energy gain was expected.
The inputs and outputs of energy and materials were calculated using the
following assumptions:
1. Electrical power required to process 1 ton of waste can be deter-
mined by using quoted electrical equipment ratings, estimating
how long each piece of equipment would have to operate to pro-
cess 1 ton of waste, and then converting to Btu assuming 30 per-
cent conversion efficiency from fossil fuel.
2. No. 2 fuel oil needed to pyrolyze the waste is fed at a rate of
7.1 gallons per ton.
3. The waste has a heat value of 4,600 Btu per pound.
4. The two bulldozers use 16 gallons of fuel per hour.
5. Other internal combustion engine vehicles (crane, loader, etc.) use
10 gallons per day.
The calculations are only approximate and are based on scale-up factors
and engineering estimates (Figure 6). The results show a 51 percent plant effi-
ciency (output energy divided by input energy). A 51 percent efficiency is
relatively good compared to that of other utility plants (fossil-fuel-fired steam
or electric plants, nuclear plants, waterwall incinerator, etc.); this emphasizes
the point that solid waste can replace other energy sources in an efficient
manner. It would require 670 pounds of coal or 46 gallons of oil to produce
the same amount of steam that this plant will produce from 1 ton of solid
waste. No attempt was made to compute the energy savings realized by re-
cycling the recovered iron or aggregate.
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the products and
their marketing
Steam
A steam-generating plant must have a nearby market because the transpor-
tation of steam over great distances is uneconomical. Such a market exists in
Baltimore. Steam generated at the rate of 200,000 pounds per hour is trans-
ported in a 4,500-ft steam main to an existing Baltimore Gas and Electric
Company (BG&E) steam distribution line. It will be used to heat and cool
buildings in the downtown area.
BG&E has entered into a 5-year contract to purchase the steam from the
pyrolysis plant at a price of $0.81 per 1,000 pounds of steam, which is based
on a cost of $3.70 per barrel of No. 6 heavy fuel oil as delivered to the buyer.
For each $l-per-barrel increase in the cost of No. 6 oil, the price of steam is
raised about $0.22. As the cost of fuel oil has more than doubled since the
contract was signed, the revenues expected from the steam have greatly in-
creased. The steam will be delivered to the BG&E line at between 100 and
260 pounds per square inch, at a temperature not to exceed 415 F, and at a
rate that does not fluctuate more than 15 percent. During the months of
July and August only 100,000 pounds per hour will be delivered.
The boilers are designed to limit the solid content of the steam to 3 parts
per million. Feed-water treatment will maintain the pH of the steam con-
densate between 6.8 and 9.0.
Ferrous Metal
About 70 tons of ferrous metal will be magnetically separated from the
pyrolysis reactor residue each day. The iron is clean and reasonably free of
contaminants (Table 2), and can be used either as melting stock for the steel
and foundry industry or as precipitation iron in the copper industry. The
ferrous fraction could be used by a detinner if it is recovered before pyrolysis,
and separation of ferrous metals before pyrolysis will be tested after the
plant is in operation.
The market for the ferrous fraction will determine the process used in re-
moving the iron from the waste stream. There are three basic markets for this
iron: the copper precipitation industry, the detinning industry, and the steel
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TABLE 2
Quality of Ferrous Metal Recovered
Bulk density
Iron
Contaminants
from Pyro lysis Residue
35 pounds per cubic foot
98.85% by weight
1.1 5% by weight
Chemical analysis
Component Percent
Iron 98
Tin
Carbon
Copper
Nickel
Lead
Manganese
Silicon
Chromium
.850
.153
.150
.150
.140
.088
.048
.045
.035
Component Percent
Antimony .020*
Sulfur .016
Phosphorus .015
Cobalt .010*
Molybdenum .010*
Titanium .010*
Vanadium .010*
Aluminum .001*
Other .249
"Less than percent shown.
TABLE 3
Analysis of Glassy Aggregate Recovered
from Pyro lysis Residue
Bulk density
150 pounds per cubic foot
Component
Glass
Rock and miscellaneous
Ferrous metal
Nonferrous metal
Carbon
Percent
65
28
3
2
2
15
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industry. Each requires different characteristics in the scrap iron it uses. The
detinning industry requires tin cans that are not balled up or crushed, but
rather shredded or open so that a large surface is available for the detinning
chemicals to work properly. The copper industry needs cans that are open
and that have been detinned by some process, either thermal or chemical.
The steel industry wants scrap that is dense (crushed, shredded, or balled) and
free of tin and copper.
The Metal Cleaning and Processing Company has contracted to buy the
post-pyrolysis ferrous fraction for 38.6 percent of the weekly quoted price
on No. 2 bundles as listed on the Philadelphia Market in Iron Age Magazine.
This iron will be used for steelmill feed stock.
Glassy Aggregate
The glassy residue recovered from the sink fraction in the flotation unit is
relatively metal-free (Table 3) and will be used in road construction. Balti-
more tested this material (obtained from the pilot plant) as an aggregate in
bituminous paving mixtures (asphalt) in both a laboratory and on a section of
a street in the city. The results were promising and the city is planning full-
scale street use once the material is available. City street construction specifi-
cations will be revised to allow or to require the use of this material as aggre-
gate in binder course mixes for city streets. It is anticipated that the glassy
aggregate will have a value of $2 per ton at the plant site.
Carbon Char
A carbon char residue, the float fraction from the flotation unit, is gen-
erated at the rate of 80 tons per day. This material consists of 50 percent
carbon (dry weight basis), with the rest mostly ash and glass (Table 4).
One possible use for the char is as a substitute for commercial activated
carbon used in wastewater treatment plants. Laboratory experiments have
substantiated the absorption characteristic of carbon char, and further re-
search on carbon slurry absorption is scheduled.
Char can also be used as a soil conditioner along with dried and digested
sewage sludge. This use will be tested in Baltimore. The char could be mixed
with the city's sludge, dried, and given to the public at no charge.
Until a good use for the char is developed, however, it will be disposed of
in a land disposal site.
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TABLE 4
Analysis of Carbon Char Residue
Bulk density
20-50 pounds per cubic foot
Moisture content 50% by weight
Heating value
, dry basis 7,000 Btu per pound
Analysis, dry basis
Component
Carbon
Ash and glass
Volatiles
Sulfur
Percent
50.0
45.8
4.0
0.2
Analysis of water-extractable fraction
Component
Sodium
Calcium
Copper
Magnesium
Potassium
Boron
Strontium
Iron
Molybdenum
Silicon
Phosphorus
Chromium
Lead
Tin
Vanadium
Zinc
Aluminum
Cadmium
Manganese
Silver
Titanium
Percent or parts per million (ppm)
over 30%
0.1-1.0%
0.03-0.3%
0.03-0.3%
0.03-0.3%
0.01-0.1%
0.001-0.1%
0.001%*
0.001%*
0.001%*
25 ppm*
10 ppm*
10 ppm*
1 0 ppm*
5 ppm*
5 ppm*
1 ppm*
1 ppm*
1 ppm*
1 ppm*
1 ppm*
*Less than figure shown.
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TABLE 5
Economic Estimates for the Baltimore Plant
($ per throughput ton)
Costs and revenues
Amortization*
Operating costs
Fuel
Electricity
Manpower
Water and chemicals
Maintenance
Miscellaneous
Char removal
Total
Total expenses
Revenues
Steamf
Iron
Glassy aggregate
Total revenues
Net operating cost
January 1973
$4.34
$ .89
1.06
1.02
.31
1.84
.42
.18
$5.72
$10.06
$3.89
.44
.34
$4.67
$5.39
February 1974
$5.55
$2.20
1.50
1.10
.30
1.90
.40
.20
$7.60
$13.15
$11.18
1.55
.40
$13.13
$ .02
*Approximate plant cost: in January 1973, $16 million; in February 1974,
$20 maiion.
fPrice is keyed to fuel oil price, which was $3.70 per barrel in January 1973, and
$10.63 per barrel in February 1974.
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economics
Data on the economics of the pyrolysis plant consist only of estimates at
this time (Table 5). It should also be noted that the data are very site-specific
and should not be considered necessarily applicable to other locations. Such
pertinent factors as site costs, labor and material costs, product marketability,
and plant size will naturally vary from place to place. No attempt has been
made to normalize the figures to make them applicable to other areas of the
country except in the case of capital amortization. Since the Baltimore situa-
tion is unique because an EPA grant and an MES loan are applied to the capi-
tal cost of the plant, Baltimore's actual amortization costs are not presented.
Instead, a typical 20-year, 6-percent municipal bond was used to determine
capital cost figures.
Plant throughput, based on 85 percent availability, will be 310,000 tons
per year, and all costs and revenues have been converted to dollars per ton.
At January 1973 costs and prices, the total costs per ton are estimated to be
$10.06 and total revenues $4.67, giving a net cost of $5.39. Based on Feb-
ruary 1974 costs and prices, the estimates are $13.15 for total expenses and
$13.13 for total revenues, giving a net operating cost of $0.02 per ton. The
large difference in estimated revenues between the 2 years is mostly due to
the rise in the price of steam, which is keyed to the price of fuel oil.
With the escalating cost of fossil fuel, an energy recovery plant has a good
possibility of operating at a break-even point, and might in fact make a profit
for a city.
environmental
considerations
One of the objectives of the Baltimore project is to demonstrate whether a
pyrolysis system can recover the energy and material resources in municipal
solid waste without polluting the environment. If successful the plant will:
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1. Allow BG&E to save 15 million gallons of oil annually.
2. Permit the city to dispose of much of its solid waste with lower
air emissions than is presently possible.
3. Cause steam to be produced with lower emissions than is possible
with existing boilers.
4. Enable industry to use recovered instead of virgin materials, thus
conserving resources and saving energy.
Air Emissions
Once the plant is operational,. Baltimore will be able to close down an
incinerator that does not meet clean air standards. Air emissions from the
pyrolysis plant will meet the Federal particulate emission standard of .08
grains per standard cubic foot of dry flue gas corrected to 12 percent CO2,
and the Maryland code of ,03 grains per standard cubic foot. As there is very
little sulfur in solid waste, the sulfur dioxide emissions from the plant will be
correspondingly low, under 100 parts per million. Nitrogen oxide (NOX) pro-
duction in the plant is also kept at a low level by combusting the pyrolysis
gases at a low temperature. The NOX emissions will amount to less than 50
parts per million. Unburned hydrocarbons in the exhaust will be held to just
a few parts per million of methane equivalent. The emission quality is guar-
anteed by the contractor. Moreover, the plant will be closely monitored, as a
part of the EPA evaluation, to assure that all applicable local, State, and Fed-
eral point source and ambient air quality standards are met.
Water Effluent
All process water is recycled. Occasionally recycled water will exceed
needs, and such excess water will be discharged into the sanitary sewer at a
maximum flow of 75 gallons per minute. Any water so discharged will be
treated at Baltimore's Back River Plant and will not significantly change the
influent characteristics of the treatment plant. The Back River Plant employs
both primary and secondary treatment processes.
Land Pollution
The only plant output that may be disposed of on land is the carbon char,
if use of this material is not possible. The char contains about 1 percent of
water-soluble material, and disposal will have to be engineered to prevent the
char leachate from entering the groundwater system.
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Figure 7. Operation of the entire plant is monitored and controlled from this
panel. The TV screens above the panel show what is on the conveyors feeding into the
shredders.
Noise
The hammermilling of solid waste is a noisy operation. The shredders are
located above ground in soundproofed structures. All other equipment that
could cause noise pollution is also protected. All applicable noise regulations
will be met, and ambient noise at the plant boundaries will be within stand-
ards for this industrially zoned site.
Summary
There will be no significant adverse environmental effect from the opera-
tion of this plant. On the contrary, if the process proves successful, the city
can reduce total pollution associated with present practices of landfilling, in-
cineration, use of iron ore in steelmaking, and use of fossil fuels to generate
steam.
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guarantee
Monsanto is responsible for the complete design, construction and start-up
of the plant, all at a fixed price. The "turn-key" contract calls for Monsanto
to turn over to Baltimore a completely operational facility. Additionally, the
contract provides for up to $4 million in performance penalties if the plant
fails any of the following requirements: (1) Air emissions will meet
existing Federal, State, and local air pollution regulations. (2) Plant capacity
will average a minimum of 85 percent of design capacity for an identified 60-
day period. (3) Putrescible content of residue will be less than 0.2 percent.
project evaluations
During the first year of operation, the pyrolysis plant will be evaluated for
its technical and economic characteristics and for its environmental effects by
an independent contractor hired by EPA, and the results will be disseminated
to the public. Each processing step will be evaluated to determine its ability
to meet the original design requirements, its operation and maintenance costs,
its economic balance, its energy balance, and so forth. Plant effluents and
products will be analyzed to make sure they meet specifications.
An interim report will be published in the spring of 1976. A final report
will be published in mid-1977.
Once operational, the plant will be open to the general public. For infor-
mation about visiting hours and tour arrangements, contact Elliot Zulver,
Project Officer, Bureau of Utility Operations, 900 Municipal Building, Balti-
more, Maryland 21202.
questions and answers
Q Our city collects newspapers separately from other waste so that
the paper can be sold to wastepaper dealers. How would this reduction in the
paper content of municipal waste affect a pyrolysis plant?
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A Generally the tonnage and Btu content of the waste will be re-
duced only by a small percentage (see Recommended Reading). The presence
of an energy recovery plant should not of itself deter a city from this environ-
mentally sound practice. Wherever feasible, wastepaper should be recycled
rather than used for fuel.
Q What if there is no market for steam in our city? Can we still use
a gaseous pyrolysis system?
A The lack of a market for steam has severely limited solid-waste-to-
steam projects. This pyrolysis system can be adapted so that a steam market
is not necessary. Monsanto feels that the pyrolysis gas can be cleaned and
piped a short distance to an industrial or utility boiler and burned along with
the normally used fossil fuel. Another option proposed by Monsanto is to
use the steam to generate electricity on site.
Q What would happen to a Baltimore-type system if measures are
implemented to reduce the generation of waste, like banning the throwaway
beverage container?
A If throwaway beverage containers are eliminated, there would be
a small reduction in the noncombustible fraction of the waste. The ferrous
fraction and the volume of glassy aggregate would probably be cut in hah",
but the overall economics of the plant would still be viable. Revenue would
be reduced, but as energy production is the primary moneymaker, the reduc-
tion would not be appreciable. The energy savings from eliminating throw-
aways would far overshadow the slight drop in revenue. If many measures to
reduce waste materials were adopted, however, the 1,000-ton-per-day plant
may have to draw waste from a larger population base in order to operate at
an economical level.
Q // new resource recovery technology is developed in the next few
years, won't Baltimore have an obsolete plant?
A In our technological society, things become obsolete quickly;
however, they remain usable. The Baltimore plant has a useful life of 15 to
20 years. After that time, if new and better technology is available, it will
probably be used instead. In the meantime, we must move ahead with the
best technology that is available now.
Q We have about 5 years of life remaining in our landfill. Why
should we worry about a resource recovery plant now?
A You should be planning now. The lead time needed to get a re-
source recovery facility underway is from 3 to 5 years. And there is the basic
goal of conservation—we are running out of things and we should not plan to
go on burying materials and energy when we have the means to recover these
resources.
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RECOMMENDED READING
The following publications are available from:
Solid Waste Information Materials Control Section
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
1. Energy conservation through unproved solid waste management,
by Robert A. Lowe, with appendices by Michael Loube and
Frank A. Smith. Environmental Protection Publication SW-125.
Cincinnati, U.S. Environmental Protection Agency, 1974. 39 p.,
app.
2. Energy recovery from waste; solid waste as supplementary fuel in
power plant boilers, by Robert A. Lowe. Environmental Protec-
tion Publication SW-36d.ii. Washington, U.S. Government Print-
ing Office, 1973. 24 p.
3. Markets and technology for energy recovery from solid waste, by
Steven J. Levy. Environmental Protection Publication SW-130.
Washington, U.S. Environmental Protection Agency, 1974. 31 p.
4. Pyrolysis of municipal solid waste. Waste Age, 5(7): 14-15,17-20,
Oct. 1974.
5. List of pyrolysis companies, by J. Robert Holloway. (In prepara-
tion.)
6. The effect of paper recovery on the characteristics of solid waste
as a fuel, by J. Robert Holloway and John H. Skinner. (In prep-
aration.)
7. The demonstration of systems for recovering materials and energy
from solid waste, by John H. Skinner. Presented at the National
Materials Conservation Symposium, National Bureau of Standards,
Gaithersburg, Md., Apr. 29, 1974. [Washington], U.S. Environ-
mental Protection Agency, 1974. 20 p.
8. Decision-makers guide in solid waste management, compiled by
Robert A. Colonna and Cynthia McLaren. Environmental Protec-
tion Publication SW-127. Washington, U.S. Government Printing
Office, 1974. 157 p.
9. Recovering resources from solid waste using wet-processing;
EPA's Franklin, Ohio, demonstration project, by David G. Arella.
Environmental Protection Publication SW47d. Washington, U.S.
Government Printing Office, 1974. 26 p.
U0l069b
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