Recovery of particulate matter from exhaust gas is vital for any industry from two aspects:
To avoid pollution problems
Recovery of finished product-increasing the plant yield
For recovering particulate matter different options available are - cyclones, venturi, scrubbers, bag air filter, pollution control bag filter, electrostatic precipitates etc. Out of these bag filter becomes the best choice if following are dominant selection criterias:
Material is expensive and hence high collection efficiency is desired.
Particulate size is very fine.
Material recovery in powder form is desirable & not in solution form.
Working Principle of Bag Filter :
The dust-laden air enters the bag filter.
The dust /powder separates inside the bag filter chamber.
The air is uniformly distributed avoiding channelling while the powder is separated.
Initially a coat of material forms on the bags. Subsequently, the coat acts as the filtering medium.
The dust is accumulated on filter elements while the air passes through the filter bags from outside to inside.
The accumulated powder is dislodged from the bags by reverse pulsejet air intermittently.
The dislodged powder falls on bottom cone and is discharged through powder discharge valves.
The dust free air is sucked by induced draft fan and is exhausted to atmosphere.