TM 5-815-1/AFR 19-6
fluidize. Waste is fed above the bed and then
chamber. An auxiliary fuel burner is
mixes with the media where it burns.
normally provided underneath the grate. The
Fluidized bed incinerators are normally self
units are normally natural draft (no fans).
sustaining and require an auxiliary fuel
Emissions from single chamber units are high
burner only for startup. Fluidizing air is
because of incomplete combustion.
supplied by a centrifugal blower. Ash leaves
Multiple chamber incinerators. Multiple
(2)
the fluidized bed incinerator when it becomes
chamber refractory lined incinerators nor-
fine enough to be carried out by the flue gas.
mally consist of a primary chamber, a mixing
Fluidized bed incinerators are capable of
chamber and a secondary combustion cham-
burning most types of liquid or solid waste.
ber. The primary chamber is similar to a
c. Sludge incinerators. Sludge incinerators handle
single chamber unit. Air is fed under the
materials high in water content and low in heat content.
grate and through overfire air ports.
Two types of incinerators are normally used for sludge
Secondary air is added in the mixing
incineration.
chamber. Combustion is completed in the
(1) Multiple hearth incinerators. Multiple hearth
secondary combustion chamber where some
incinerators consist of vertically stacked
settling occurs. These units are also normally
grates. The sludge enters the top where the
natural draft.
exiting flue gas is used to drive off the
Conical incinerators. Conical incinerators
(3)
moisture. The burning sludge moves through
known commonly as "tee-pee" burners have
the furnace to the lower hearths. Ash is
been used primarily in the wood products
removed from under the last hearth.
industry to dispose of wood waste. Since
(2) Fluidized bed incinerator. Fluidized bed
they cannot meet most local particulate
incinerators are particularly well suited for
emission requirements, and since wood
sludge disposal because of the high heat
waste is becoming more valuable as a fuel,
content of the bed media. Heat from the
conical incinerators are being phased out.
combustion of the sludge is transferred to the
Trench incinerators. Trench incinerators are
(4)
bed media. This heat is then transferred back
used for disposal of waste with a high heat
to the incoming sludge, driving off the
content and a low ash content. The
moisture.
incinerator consists of a U-shaped chamber
with air nozzles along the rim. The nozzles
2-6. Particulate emission standards
are directed to provide a curtain of air over
The Clean Air Act requires all states to issue regula-
the pit and to provide air in the pit.
tions regarding the amount of particulate emission
Controlled-air incinerators. Controlled-air
(5)
from incinerators. Each state must meet or exceed the
incinerators consist of a refractory lined pri-
primary standards set forth by the federal act, limiting
mary chamber where a reducing atmosphere
particulate emissions for incinerators with a charging
is maintained and a refractory lined
rate of more than 50 tons per day of solid to .08 grains
secondary chamber where an oxidizing
per standard cubic foot (gr/std ft3) of dry gas at 12
atmosphere is maintained. The carbon in the
percent carbon dioxide (CO2). Federal guidelines for
waste burns and supplies the heat to release
sewage sludge incinerators limit emissions to 1.3
the volatiles in the waste in the form of a
pounds (lbs) per ton of dry sludge input and opacity to
dense combustible smoke. Overfire air is
20 percent maximum. No federal guidelines currently
added between chambers. The smoke is
exist for gaseous emissions. State and local regulations
ignited in the secondary chamber with the
may meet or exceed the federal guidelines. These reg-
addition of air. Auxiliary fuel burners are
ulations are subject to change and must be reviewed
sometimes provided in the secondary
prior to selecting any air pollution control device.
chamber if the mixture does not support
combustion. Air for this type of incinerator is
2-7. Particulate emission estimating
provided by a forced draft fan and is
In order to select a proper pollution control device, the
controlled by dampers in order to provide the
quantities of particulate emissions from an incinerator
proper
distribution.
Controlled-air
must be measured or estimated. Measurement is the
incinerators are efficient units with low
preferred method. For new incinerator installations
particulate emission rates.
where particulate emissions must be estimated, tables
Fluidized bed incinerators. Fluidized bed
(6)
2-3 and 2-4 should be used unless concurrent data
incinerators consist of a refractory lined ver-
guaranteed by a qualified Vendor is provided.
tical cylinder with a grid in the lower part
a. Factors affecting emission variability. The quan-
that supports a bed of granular material, such
tity and size of particulate emissions leaving the fur-
as sand or fine gravel. Air is blown into the
nace of an incinerator vary widely, depending upon
chamber below the grid causing the bed to
2-3
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