The working principle of bag filters revolves around three key stages: filtration, separation and removal.
1. Filtration:
Air containing particulate matter enters the bag filter system. Here, the "bags" made of fabric filters play a key role. As dirty air passes through these fabric bags, particles are captured on the surface, allowing clean air to pass through. The quality of the fabric used improves the efficiency of this process, and the fabric is designed to capture the finest particles.
2. Separation:
Over time, a layer of dust, called "dust cake", accumulates on the bags. Rather than being an obstruction, this layer of dust cake increases the efficiency of the filter. The dust cake acts as an additional filter layer, capturing fine particles that may have passed through the initial fabric layer. However, in order to maintain efficiency, this layer of dust cake cannot be too thick.
3. Removal:
This leads to the last stage - removal. Bag filters use various mechanisms to remove the dust cake from the bag. Common methods include mechanical shaking, reverse air and pulse jet cleaning. For example, in pulse jet cleaning, short pulses of compressed air are passed through the bag, shaking the dust off into a hopper for disposal.
