Bag filter systems are used for removing particulate materials from process and
general ventilation air as well as to recover valuable products from several
Designed to handle heavy dust loads, a dust collector system consists of a blower,
dust filter (like the bag filters), a filter-cleaning system,
and a dust receptacle or dust removal system.
Removing particulates from flue gas from industrial boilers is
one of the applications relevant for air pollution control.
Commonly known as baghouses, fabric collectors use filtration to separate dust
particulates from dusty gases. They are one of the most efficient and cost effective
types of dust collectors available and can achieve a collection efficiency
of more than 99% for very fine particulates.
Dust-laden gases enter the baghouse and pass through fabric bags that act as filters.
The bags can be of woven or felted cotton, synthetic, or glass-fiber material
in either a tube or envelope shape.
The high efficiency of these collectors is due to the dust cake formed
on the surfaces of the bags. The fabric primarily provides a surface
on which dust particulates collect through the following four mechanisms:
A combination of these mechanisms results in formation of the dust cake on the filter,
which eventually increases the resistance to gas flow. The filter must be cleaned periodically.
- Inertial collection - Dust particles strike the fibers placed perpendicular to the gas-flow direction instead of changing direction with the gas stream.
- Interception - Particles that do not cross the fluid streamlines come in contact with fibers because of the fiber size.
- Brownian movement - Submicrometre particles are diffused, increasing the probability of contact between the particles and collecting surfaces.
- Electrostatic forces - The presence of an electrostatic charge on the particles and the filter can increase dust capture.