The Filtration Process of Bag Filter

The external filter dust collector is equipped with a cylindrical support bag cage inside each filter bag, and the gas containing dust flows from the outside to the inside of the filter bag. So, the dust is filtered and captured by the outer side of the filter bag, and the clean gas is discharged from the upper part through the inner side. The clean room is equipped with compressed air pipes, which use the pulse airflow sprayed out by the compressed air pipes to shake off dust. The shell, funnel, and other vibrating structures are the same and in a closed state. The dusty gas sent in from the upper part of the funnel is divided and rises to each filter bag, where it is filtered and captured. The filtration performance of an internal filter dust collector is similar to that of an external filter dust collector.

The new filter bag mainly captures dust larger than 1 μ m during the initial operation, and the capture mechanism includes inertia, screening, shielding, electrostatic settling, and gravity settling. The primary adhesion layer of dust formed on the filter cloth surface can also capture particles below 1 μ m and control diffusion. These forces are influenced by the size, density, fiber diameter, and filtration speed of dust particles.

The bag filter processes air with a dust concentration of 0.5-100g/m3. Therefore, within a few minutes of starting to move, a layer of dust adhesion is formed on the surface and inside of the filter cloth. This adhesive layer is also known as a primary adhesive layer or filter membrane.

If an adhesive layer is formed, it plays a filtering and trapping role. The reason is that many micropores are formed in the dust layer, with a porosity of 0.8~0.9, which produce a screening effect. The lower the filtration speed, the smaller the micropores, and the higher the porosity of the dust layer. So, the efficient capture process largely depends on the filtration speed.