TM 5-815-1/AFR 19-6
(3) NOx. Furnace design and firing methods are
(3) When particulates are the controlled
pollutant, primary collection devices
employed. The primary zone is fired with lim-
commonly used are:
ited air to maintain a reducing atmosphere
mechanical collectors; wetted baffles; and
and the secondary zone uses an oxidizing
atmosphere to provide a controlled low-tem-
(4) The final collection fo small particulate mate-
perature flame with minimum excess air.
rial is usually accomplished with one of the
(4) Opacity. Opacity is controlled by limiting par-
ticulate emissions and by properly designed
-- venturi or orifice-type scrubber -electrostatic
-- fabric filter.
12-6. Applications of emission control
c. Incinerator vapor and odor control. Objection-
systems for incinerators
able vapors and odors in incinerator exhaust streams
sometimes necessitate specialized control systems.
Refuse incinerators are type categorized as: municipal;
Odorous components present downstream of con-
industrial; commercial; and sludge. NSPS cover par-
ventional cleaning systems are usually organic in gas-
ticulate emissions only. However, incineration of many
eous or fine particulate form. Several methods
solid, liquid, and gaseous wastes will produce noxious
available for their control are discussed below.
gases that require special treatment.
(1) Afterburners. Direct thermal incineration can
a. Municipal incinerators. Optimum control of
be utilized to oxidize odorous fumes. A fume
incinerator particulate emissions begins with proper
incineration system, or afterburner, basically
furnace design and careful operation. A proper design
consists of a gas or oil-fired burner mounted
includes: a furnace/grate system appropriate to the
to a refractor-lined steel shell. Odorous
waste; an adequate combustion gas retention time and
vapors and particulate matter are exposed to
velocity in the secondary combustion chamber; a suit-
a high temperature flame (1200 to 1400
able underfire and overfire air system; and establishing
degrees Fahrenheit) and are oxidized into
the optimum underfire/overfire air ratios.
water vapor and carbon dioxide. The
(1) for compliance with NSPS it is necessary to
principal advantages of direct thermal
utilize gas cleaning equipment and to
incineration of odorous pollutants are
optimize operating conditions for the furnace.
simplicity, consistent performance, easy
(2) Particulates. May be controlled with mechan-
modification to accommodate changes in
ical collectors; settling chambers; after
standards, and ease of retrofit. The major dis-
burners; and low efficiency scrubbers used as
advantage is the uncertainty and expense of
precleaners. These must be followed by an
fuel supply usually natural gas.
electrostatic precipitator or a high efficiency
(2) Vapor condenser. Vapor condensers are uti-
venturi/orifice scrubber for final cleaning.
lized to control obnoxious odors, particularly
Fabric filters may be used if emissions gas
m processes where the exhaust gases contain
temperature is maintained below the
maximum temperature rating of fabric media
be either the direct contact type, or shell and
being used. This will usually require water
tube surface condensers. The resulting con-
spray injection for evaporative cooling of the
densate is rich in odorous material and can be
sewered of treated and disposed of by other
(3) Odor control is frequently required and can
conventional methods. (See paragraph 7-4 for
be accomplished with after-burners
further information on treatment and disposal
strategically located in the furnace to oxidize
of waste materials.) Condensers are often
the odorous gases.
used in conjunction with an afterburner. In
b. !Industrial and commercial incinerators. Design
such a system, exhaust gases are condensed
of the incinerators and emissions control requirements
to ambient temperature before incineration,
reducing gas stream volume by as much as 95
waste that is incinerated.
percent and reducing moisture content.
(1) Single chamber and conical (Teepee) type
Lowering gas volume and moisture content
incinerators will not meet current NSPS emis-
can substantially reduce the cost and fuel
requirements of the afterburner assembly.
chamber incinerators with
(3) Catalytic oxidation. Incineration of odorous
pollutants in the presence of a suitable
fluidized-bed incinerators including sludge
catalyst can lower the temperature required
incinerators may be equipped with one or
for complete combustion and reduce the
more of the previously discussed or following
overall reaction time. Advantages of catalytic
gas-cleaning systems to meet NSPS.