Bag Filter Working Principle

The working mechanism of the bag filter is that after the dust-laden flue gas enters the dust collector through the duct through the wind force of the induced draft fan, it passes through the first-level baffle (gravity sedimentation), the large specific gravity dust is intercepted and then settles into the ash hopper. After passing through the cloth bag, the fine dust is filtered by the cloth bag, and the clean air is discharged to the atmosphere along the chimney. In addition, the filter material mainly relies on inertial collision to capture coarse dust, while the fine dust mainly relies on diffusion and screening. The dust layer of the filter material plays a major role in filtering fine dust.

1.Gravity sedimentation-when the dust-containing gas enters the bag filter, the dust with large particles and high specific gravity will settle down under the action of gravity after hitting the baffle, which is exactly the same as the sedimentation chamber.

2.Screening effect-when the particle diameter of the dust is larger than the gap between the fibers of the filter material or the gap between the dust on the filter material, the dust is blocked when the airflow passes through, which is called the sieving effect. When the dust accumulated on the filter bag increases to form a powder cake layer, this effect becomes more significant.

3.Inertial force action-when the airflow passes through the filter material, it can pass around the fiber, and the larger dust particles still move in the original direction under the action of inertial force, and then collide with the filter material and be captured.

4.Thermal movement effect-light and small dust (below 1 micron), moves with the airflow, very close to the airflow streamline, can bypass the fiber. However, after they are collided by gas molecules that are in thermal motion (ie, Brownian motion), they change the original direction of motion, which increases the chance of contact between dust and fibers and enables dust to be captured. When the fiber diameter of the filter material is finer, the void ratio is smaller, and the capture rate is higher, so it is more conducive to dust removal.