The surface filtering mainly uses the mesh material, and the depth filtering uses the felt material. Their differences are as follows:
- Screen material (nylon monofilament, metal monofilament) will directly trap impurities in the filter on the surface of the material. The advantage is that the monofilament structure can be cleaned repeatedly, and the consumption cost is low; while the disadvantage is the surface filtration mode, which is easy to cause clogging of the filter bag surface. This type of product is most suitable for low-precision coarse filtration occasions, with a filtration accuracy of 25-1200μm.
- Felt materials (needle-punched cloth, melt-blown non-woven fabric) are common deep three-dimensional filter materials, which are characterized by loose fiber structure and high porosity to increase the tolerance of impurities. This kind of fiber material belongs to the double retention mode , That is, the larger particles of impurities are trapped on the surface of the fiber, and the fine particles are trapped in the deep layer of the filter material, so the filtration has higher filtration efficiency. In addition, the high-temperature surface heat treatment, that is, the application of instant sintering technology, can effectively prevent filtration. Fibre fluids are washed away at high speed and dispersed; the felt material is discarded (one-time use) with a filtration accuracy of 1-200 μm.
The material properties of the filter felt are as follows:
Polyester — the most commonly used filter material fiber, good chemical resistance, working temperature is less than 170-190 ℃
Polypropylene — used for liquid filtration in the chemical industry, has excellent resistance to acids and alkalis, working temperature is less than 100-110 ℃
Wool — good solvent resistance, but not suitable for acid and alkali filtration
Nylon — has good chemical resistance (except acid resistance), working temperature is less than 170-190 ℃
Fluoride — has the best temperature and chemical resistance, working temperature is less than 250-270 ℃