Secondly, the fiber layer filtration mechanism
The fiber layer is a porous aggregate composed of many single fibers or yarns arranged in a certain structure. In addition to the above-mentioned inertial effect, interception effect, diffusion effect, electrostatic effect, and gravity effect, the filtering mechanism of the fiber layer also has a mesh effect.
When the dust-containing airflow passes through the fiber layer, the dust in the gas with a particle size larger than the fibers, the pores between the yarns or the pores between the dust is collected by screening, which is called the screening effect.
In the field of industrial dust removal, there are two types of commonly used fiber layer filter materials, organic woven cloth and needle felt. The structure and manufacturing process of the two types of fibrous layer filter materials are not the same, and the initial filtration mechanism is also different.
- Filtration mechanism of the woven fiber layer
Woven fabric is a two-dimensional planar structure fiber assembly in which fibers are spun into yarn and then woven into various textures. The fiber layer of the woven fabric is thin, usually less than 1mm, the fibers are tightly bound and the pores are small, the cross pores between the lines are large, the channels are straight, the pore diameter is about 30~60μm, and the overall void ratio is about 35%~50% Among them, the gap between the lines which actually plays the role of ventilation and filtration is only 30-40%. When the dust-containing airflow passes through the fiber layer, the dust is mainly affected by the inertia effect, interception effect, diffusion effect, and screening effect. Part of the dust particles adhere to the surface of the fiber, are trapped and accumulated, and then bridged to derive a dust layer, and some fine dust particles penetrate the fiber layer. During dust cleaning and regeneration, the ash accumulation is easy to loosen and disperse due to the straightness of the pores in the fiber layer. From the analysis of the filtration mechanism, although the initial filtration of the woven fabric fiber layer has a certain body filtration function, it is closer to the surface filtration function.
- Filtration mechanism of needle felt fiber layer
Acupuncture felt is a three-dimensional spatial structure fiber assembly made by mechanically or chemically rolling and entanglement of fibers, or by laminating fibers into a web (fleece), and then using needle-punching (or spunlace) to cross-entangle.
The needle felt fiber layer is relatively thick, usually 1.5~2.5mm thick, forming a void structure between the fibers, the channels are tortuous and evenly distributed, the pore size is about 10~40μm, and the porosity can reach 70~80%. When the dust-containing airflow passes through the fiber layer, the dust is mainly affected by the combined effects of inertia effect, interception effect, diffusion effect, and screening effect. Part of the dust particles are entrapped by the fibers, and part of the dust particles penetrate into the pores inside the fiber layer, forming a joint catching body with the fibers, and then expanding to the surface to form a dust layer, and a small amount of fine dust penetrates the fiber layer. During dust cleaning and regeneration, due to the twists and turns in the fiber layer, dust accumulation is not easy to escape. From the analysis of the filtering mechanism, the filtering mechanism of the initial needle-punched felt fiber layer is similar to that of the air filter, and the main body filter is the main body. With the establishment of the surface dust layer, the transition to the surface filter gradually.