Agriculture Reference
In-Depth Information
cylinder-baffle system, and falls with gravity to the lower end of the cylinder.
The heated upward-moving off-gases are collected, monitored for chemical con-
stituents, and subsequently treated as appropriate prior to release, while the ash
falls with gravity to be collected, monitored for chemical constituents, and treated
as needed before ultimate disposal. The newer rotary kiln systems 15 consist of a
primary combustion chamber, a transition volume, and a fired afterburner cham-
ber. After exiting the afterburner, the flue gas is passed through a quench section
followed by a primary APCS. The primary air pollution control system (APCS)
can be a venture scrubber followed by a packed-column scrubber. Downstream
of the primary APCS, a backup secondary APCS, with a demister, an activated-
carbon adsorber, and a high-efficiency particulate air (HEPA) filter can collect
contaminants not destroyed by the incineration.
The rotary kiln is applicable to the incineration of most organic contaminants,
it is well suited for solids and sludges, and in special cases, liquids and gases can
be injected through auxiliary nozzles in the side of the combustion chamber.
Operating temperatures generally vary from 800 to 1650 C. Engineers use labo-
ratory experiments to design residence times of seconds for gases and minutes or
possibly hours for the incineration of solid material.
Multiple-Hearth System
In the multiple-hearth system illustrated in Figure 3.8 contaminants in solid or
sludge form are generally fed slowly through the top vertically stacked hearth; in
special configurations hazardous gases and liquids can be injected through side
nozzles. Multiple-hearth incinerators, historically developed to burn municipal
wastewater treatment biosolids, rely on gravity and scrapers working the upper
edges of each hearth to transport the waste through holes from upper hotter
hearths to lower cooler hearths. Heated upward-moving off-gases are collected,
monitored for chemical constituents, and treated as appropriate prior to release;
the falling ash is collected, monitored for chemical constituents, and treated prior
to ultimate disposal.
Most organic wastes generally can be incinerated using a multiple-hearth
configuration. Operating temperatures generally vary from 300 to 980 C. These
systems are designed with residence times of seconds if gases are fed into the
chambers, to several hours if solid materials are placed on the top hearth and
eventually allowed to drop to the bottom hearth, exiting as ash.
Liquid Injection
Vertical or horizontal nozzles spray liquid hazardous wastes into liquid injection
incinerators designed especially for the task or as a retrofit to one of the other
incinerators discussed here. The wastes are atomized through the nozzles that
Search WWH ::




Custom Search