Page 292 - Materials Chemistry, Second Edition

CAT3525_C09.qxd 2/8/2005 10:11 AM Page 263
Incineration of MSW 263

Burning spray Vapor
of liquid waste
vaporization Fume nuclei

Coagulation
Reducing
environment
Chlorides,
sulfides, Fume
Ash Chemical Oxides, etc Fly ash
particle reactions

Entrainment
Air and
gravity
Burning MSW
Ash
Residuals
FIGURE 9.8 Transformations of inorganics during combustion of MSW (U.S. EPA, EPA/625/R-93/008, 1993).

or other energy all produce noise. Therefore, worker safety must be addressed and the facility
should be sited such that local populations are considered.
MSW is odoriferous. Organics generated by decomposition of putrescibles can be detected at
low concentrations in ambient air over substantial distances. The most significant sources of odor
are the tipping floor, storage pits, and shredders. Sometimes the flue gases themselves will carry a
strong odor. The extent of odor production and dispersal (and therefore effects on workers and local
populations) is related to air temperature, barometric pressure, humidity, wind direction, and wind
speed.
The ideal odor control scenario is to contain odors within the facility boundary. One possible
solution is to apply negative air pressure (suction) within the tipping area and recycle the withdrawn
air into the incinerator. The gases can also be passed through a charcoal filter system which will
capture foul-smelling organic vapors. An additional precaution to reduce odor production is to
require collection vehicles to keep compartments closed except only when tipping wastes. One of
the best preventative actions for odor impact, however, involves proper siting of the facility.
Residential neighborhoods and other sensitive areas must be avoided in siting. The facility is best
sited in an area zoned for heavy industry.

9.5 AIR POLLUTION CONTROL
There is a wide range of incinerator air pollution control devices available, ranging from a series of
simple baffles to trap particulates, to scrubbers designed to remove certain acid gases. Many of
these technologies, although high in capital costs, are extremely effective in removing specific air
pollutants. The proper choice of equipment depends not only on desired emission quality and quan-
tity but also on conditions outside the incineration system. For example, a lack of local water sup-
ply will restrict the use of wet scrubbers.

9.5.1 THE ELECTROSTATIC PRECIPITATOR
Many large municipal incinerators employ the electrostatic precipitator (ESP) for flue gas cleaning,
specifically for the removal of particulate matter (Figure 9.9). The ESP can remove particles down
to fractions of a micron and are about 99% effective.