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Dust
collectors are utilized in processes to recover valuable granular
solid, powder from process streams or remove granular solid
pollutants from exhaust gases prior to venting to the atmosphere.
Dust collection is a process that collects process-generated
dust from the source point on a continuous basis. Dust collectors
may be of single unit construction, or a collection of devices
used to separate particulate matter from the process air.
They are often used as an air pollution control device to
maintain air quality.
Dust
collectors can be configured into one of five common types,
ambient units, collection booths, downdraft tables, source
collector or portable units, and stationary units. Ambient
units are free-hanging systems for use when applications limit
the use of source-capture arms or ductwork. Collector booths
require no ductwork, and allow the worker greater freedom
of movement. They are often portable. A downdraft table is
a self-contained portable filtration system that removes harmful
particulates and returns filtered air back into the facility
with no external ventilation required. Portable units are
for collecting dust, mist, fumes, or smoke at the source.
An example of a stationary collector is a baghouse.
Important
parameters in specifying dust collectors include airflow,
velocity of the air stream created by the vacuum producer,
system power, the power of the system motor, usually specified
in horsepower; storage capacity for dust and particles, and
minimum particle size filtered by the unit.
Systems
for fines removal may only contain a single filtration system
(such as a filter bag or cartridge). However, some dust collection
systems utilize a primary and secondary separation / filtration
system. Furthermore, some units may have third and fourth
stage filtration. All separation and filtration systems used
within the unit should be specified. A baghouse is an air
pollution abatement device used to trap particulate by filtering
air streams through large fabric bags. They are typically
made of glass fibers or fabric. A cyclone separator or slant
screen separator is an apparatus for the separation of fine
particles suspended in air. A dust collection system can incorporate
a series of disposable or cleanable pre-filters, a disposable
vee-bag or cartridge filter. HEPA or carbon final filter modules
can also be added. Various models are available, including
free-hanging or ducted installations, vertical or horizontal
mounting, and fixed or portable configurations. Filter cartridges
are made out of a variety of synthetic fibers and are capable
of collecting sub-micronic particles without creating an excessive
pressure drop in the system. Filter cartridges require periodic
cleaning. A wet scrubber, or Venturi scrubber, is similar
to a cyclone but it has an orifice unit that sprays water
into the vortex in the cyclone section, collecting all of
the dust in a slurry system. The water media can be recirculated
and reused to continue to filter the air. Eventually the solids
must be removed from the water stream and disposed of.
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