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Dust Property Selection Filter Bags
Feb 01, 2018

Wettability and adhesion of dust

The wettability and wettability of dust can be characterized by wetting angle. The hydrophilic and hydrophobic properties of dust are usually described as less than 60 °and 90 °respectively. The viscosity force increases, the fluidity and the charge property decrease, and adheres to the surface of the filter bag. Over time, the ash cleaning fails and the dust cake is formed. Some dusts such as CaOO, CaCl1, KClC, MgCl 2, are added to the surface of the filter bag. NaCO3 and so on moisture absorption further chemical reaction, carries on the moisture release paste bag, this is the bag dust collector most taboo.

Therefore, for wettability, moisture dust, the selection of filter bag should pay attention to the filter bag smooth, not pile and hydrophobicity. For the dust with strong adhesion, filamentous fabric filter bag, or needle felt filter bag treated by surface burning, calendering and mirror surface treatment, should be used for impregnation and coating. Film-mulching technology should be fully utilized. From the filter bag material, nylon, glass fiber superior to other varieties.

Flammability and charge property of Dust

Under certain concentration, the sparks in the air will burn or explode. The sources of dust combustion or explosion are usually caused by friction sparks, electrostatic sparks, incandescent particles, etc. This is because the chemical fiber filter bag is usually easy to charge, if the dust charged at the same time, it is easy to generate sparks. So for flammable and easily charged dust such as pulverized coal, coke powder. Aluminum oxide powder and magnesium powder should be selected as flame-retardant filter bag and conductive filter bag. For fibers with oxygen index less than 30, such as polypropylene, polyamide, polyester, and so on, flame retardant impregnation can be used.

The filter bag which is easy to charge can also be mixed with human conductive fiber in the filter bag fiber, so that the filter bag has electrical conductivity in the meridional or weft direction. The resistance is less than 109 Ω. The commonly used conductive fibers are stainless steel fiber and modified (carbonizing) chemical fiber.

Flow and friction of dust

When the flow and friction of dust is strong, the filter bag will be worn directly and the service life will be reduced. The surface is rough. The wear resistance of rhombohedral particles is 10 times greater than that of smooth spherical particles, and the wear resistance of dust particles with 90 μ m diameter is the greatest. However, when the particle size is reduced to 5 μ m, the wear resistance is very weak, and the wear resistance is proportional to the 2 / 3 power of the flow velocity and the 1.5 power of the particle diameter. The airflow velocity and its homogeneity must be strictly controlled. Among the common dust, aluminum powder, silica powder, coke powder, carbon powder and sinter powder are high wear dust. The wear resistant filter bag should be used for wear dust.

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