Dust filter material is one of the main components of the bag filter. The performance of the bag filter depends to a large extent on the performance of the filter material. The performance of the filter, mainly refers to the filtration efficiency, permeability and strength, which are related to the filter material and structure. According to bag filter
The dust removal principle and dust characteristics require the following requirements on the filter media.
(1) Large dust-holding capacity, which can retain certain permanent dust content after cleaning to maintain high filtration efficiency;
(2) It has good air permeability and low pressure loss under the condition of uniform dust holding capacity;
(3) Anti-wrinkle, wear resistance, temperature and corrosion resistance, high mechanical strength;
(4) Small moisture absorption and easy cleaning;
(5) Long service life and low cost.
Some of these requirements depend on the physicochemical properties of the fiber and some depend on the structure of the filter media. Generally, it is difficult for the filter media to meet all requirements at the same time. The appropriate filter media should be selected according to the specific conditions of use.
There are many types of filter materials used in bag filter. According to the material of the filter, there are natural fibers, inorganic fibers and synthetic fibers. In recent years, with the development of the synthetic fiber industry, there have been some new low-cost, durable filter media. In terms of fibers, there are two kinds of long fibers and short fibers. Long fiber fabrics have less fuzz on the surface and have high pressure loss in the dust layer, but are easy to remove dust. Generally, the surface of the short fiber fabric has fluff, which has good dust filtration performance and low pressure loss, but it is somewhat difficult to clean the dust. Divided by the structure of the filter, there are two types of filter cloth (plain and velvet) and felt. According to the weaving method of the filter cloth, there are three kinds of plain cloth, twill cloth and satin cloth. The overall performance of the twill fabric is good, the filtering efficiency and the cleaning effect can meet the requirements, the flexibility is good, the breathability is better than the plain weave, but the strength is slightly worse than the plain weave fabric.
1, natural fiber filter
(1) Cotton cloth is the lowest price, usually only used below 80°C. When the temperature is high, the strength is reduced sharply, acid resistance is poor, and the filtration efficiency of dust less than 10μm is low, and it is generally less used.
(2) Wool-woven filter cloth (Woolen cloth) It is usually woven into flannel with wool, thicker than cotton cloth, and the fibers are thinner than cotton fibers. It has good air permeability, low resistance, large dust holding capacity, high filtration efficiency, easy cleaning, good acid and alkalinity, but it can only be used below 90°C, and its price is much higher than cotton cloth or synthetic fiber filter cloth.
(3) Tussah silk cloth (flat silk) The surface is smooth, easy to remove dust, good air permeability, but the dust holding capacity is small, and the efficiency is low when the filter speed is large.
2, inorganic fiber filter
Mainly refers to glass fiber filter cloth, with good filter performance, low resistance, good chemical stability, high temperature resistance, non-hygroscopicity and low cost advantages. Middle alkali glass fiber cylindrical filter cloth is widely used in the gas purification of industries such as cement, smelting, carbon black and pesticides. Glass fiber filter cloths have lower filtration efficiency than natural and synthetic fiber filters. Glass fiber is not wear-resistant, does not fold, breaks easily. To improve its performance, it can be treated with aromatic silicones, PTFE, graphite, etc. After treatment, it can improve the wear resistance, hydrophobicity, acid resistance and softness. The surface is smooth and easy to clean and prolong life.
3, synthetic fiber filter
In recent years, synthetic fiber filters have developed rapidly and may replace natural fiber filters. At present, more polyamides (nylon, nylon), polyester (polyester), polyacrylonitrile (acrylic, alun), polyvinyl chloride (vinylon), polytetrafluoroethylene, etc. are used. The “208” industrial polyester velvet cloth produced in China has the advantages of large filtration capacity, high efficiency, low resistance, high strength, etc. It can withstand temperatures of 130°C and is widely used in various bag type dust collectors. Synthetic fiber can also be mixed with cotton and wool fibers, such as “Nimatite No. 2” and “Nimite Special No. 4” produced in China. The warp yarn used for warp threads is good in abrasion resistance, and the weft yarn is wool or cotton. Directly woven into a seamless cylindrical twill, with good filtration and air permeability.
4, felt filter
Rolled felt, filter felt made of synthetic fibers, and needle felt. Felt filter material has high filtration efficiency and can be filtered at high speed. With the same voidage, the average filtration speed is 2 to 3 times larger than other fabrics. However, wear and poor bending. The surface structure of the felt is loose, and the dust can penetrate deep into the interior, so it is difficult to clean the dust. It is only suitable for dust collectors that use a strong cleaning method. To this end, the felt can be subjected to various surface treatments such as fusion, resinization, or controlled heat treatment (heat and compression) to improve the felt’s trapping performance and cleaning performance. Felts are more expensive than fabrics and are therefore suitable for use in large devices, while fabrics are suitable for use in small devices.
