Working of bag house filter:

• A baghouse filter is an air pollution control device that removes particulates out of air or gas released from commercial processes or combustion for electricity generation.
• Most baghouses use long, cylindrical bags or tubes made of woven or felted fabric as a filter medium.
• For applications where there is relatively low dust loading and gas temperatures are 250 °F or less, pleated, nonwoven cartridges are sometimes used as filtering media instead of bags.
• Dust-laden gas or air enters the baghouse through hoppers that is large funnel-shaped containers used for storing and dispensing particulate and is directed into the baghouse compartment.
• The gas is drawn through the bags, either on the inside or the outside depending on cleaning method, and a layer of dust accumulates on the filter media surface until air can no longer move through it.
• When sufficient pressure drop (delta P) occurs, the cleaning process begins. Cleaning can take place while the baghouse is online filtering or is offline in isolation.
• When the compartment is clean, normal filtering resumes. Baghouses are very efficient particulate collectors because of the dust cake formed on the surface of the bags.
• The fabric provides a surface on which dust collects through the following four mechanisms:
• 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.
• 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.