Bag filters work on the principle of filtering out particulate matter from an airstream. An air stream is introduced into the filter and passes through a number ofbags. The bags are made of filter media (such as polyester, nylon or fibreglass) thathas small pores that trap particles. The particles are collected in the surface of thebags and the clean gas exit from the filter.
The bags are then routinely cleaned to remove the collected particles. The two mainways of cleaning bag filters are:
Vibrator cleaning: With this process, bags are vibrated to remove captured particles.
This is a simple and efficient but noisy way.
Pulse jet cleaning: In pulse jet cleaning a short burst of compressed air is sprayeddirectly into the filter bags. This blows captured particles out into a hopper at thebottom of the filter. Pulse jet cleaning is more effective then vibration cleaning butalso more costly.
The frequency with which a bag filter must be cleaned depends on the type of filterand the amount of particulate in the air stream. In general, a bag filter should becleaned when the pressure drop across the filter has increased to a predeterminedlevel.
Bag filters are a proven and dependable method for removing particulate matterfrom an air stream. They are also relatively inexpensive to operate and maintain.Bag filters are used in a wide variety of industries including power generation, metalprocessing, chemical manufacturing, food processing, pharmaceuticals andwastewater treatment.
