The working mechanism of bag filter is that the dust-containing flue gas passes through the filter material and the dust particles are filtered down. The filter material mainly captures coarse dust through inertial collision and fine dust through diffusion and screening. The dust layer of the filter material also has a certain filtering effect.
The dust removal effect of bag filter is related to many factors, but mainly depends on the filter material. The filter material of bag filter is cloth or felt woven from synthetic fiber, natural fiber or glass fiber. Sew cloth or felt into the cylinder or flat filter bag as required. According to the properties of flue gas, filter materials suitable for application conditions are selected. Usually, when the flue gas temperature is lower than 120℃ and the filter material is required to have acid resistance and durability, polyester flannel and polyester needled felt are often selected; In the treatment of high temperature flue gas (
In the operation of bag filter, it is very important to control the speed of flue gas passing through filter material (called filtration speed). Generally, the filtration rate is 0.5-2m/min, and the filtration rate is higher than 0. 1? The particle efficiency of m can reach above 99%, and the resistance loss of equipment is about 980- 1470 Pa. Installation points of bag filter
(1) Gravity sedimentation-When dusty gas enters the bag filter, the dust with large particles and heavy proportion will settle down under the action of gravity, which is exactly the same as the sedimentation chamber.
⑵ Screen filtration —— When the particle size of 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, which is called screen filtration. When the dust on the filter material increases, this effect is more obvious.
(3) Inertia force —— When the airflow passes through the filter material, it can bypass the fiber, while the larger dust particle zai still moves in the original direction under the action of inertia force, so it collides with the filter material and is captured.
(4) Thermal movement-light and small dust (below 1 micron) moves with the airflow, which is very close to the airflow streamline and can bypass the fiber. However, they changed their original direction of motion after being collided by gas molecules in thermal motion (Brownian motion), which increased the chance of contact between dust and fibers, so that dust could be captured. The smaller the fiber diameter, the smaller the porosity and the higher the collection rate, which is more conducive to dust removal.
Bag filter has been widely used in various industrial departments for a long time to collect non-bonded and non-fibrous industrial dust and volatiles, and the dust particles can reach 0.65438 0 micron. However, when it is used to treat gas containing water vapor, the problem of condensation should be avoided. Bag filter has high purification efficiency, that is, the efficiency of collecting fine dust can reach more than 99%, and its efficiency ratio is high.