TM 5-815-1/AFR 19-6
the heat in the gas stream evaporates the
to as a dry scrubber, is more a filter using
water from the droplets leaving a dry
sized gravel as the filter media. A bed of
powder. The gas stream is then passed
gravel is contained in a vertical cylinder
through a fabric filter or electrostatic
between two slotted screens. As the gas
precipitator where the dry product and any
passes through the interstices of the gravel,
fly ash particulate is removed. The scrubber
particulates impact on, and are collected on
chamber is an open vessel with no internals
the gravel surface. Sub-micron size particles
other than the mechanical slurry atomizer
are also collected on the surface because of
nozzles. The vessel is large enough to allow
their Brownian movement. Dust-laden
complete drying of the spray before
gravel is drawn off the bottom and the dust
impinging on the walls and to allow enough
is separated from the gravel by a mechanical
residence time for the chemical reaction to
vibrator or pneumatic separator. The cleaned
go to completion. A schematic of the system
gravel is then conveyed up and dumped on
is shown in figure 7-6. Refer to chapters 8
top of the gravel bed. The cylindrical bed
and 9 for discussion of the fabric filter or
slowly moves down and is constantly
electrostatic precipitator.
recycled.
(2) Gravel bed. The gravel bed, while referred
7-4
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