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Reasons for the high resistance of the bag filter in operation
Reasons for the high resistance of the bag filter in operation
For a bag-type dust collector, its design philosophy is whether it is qualified and its operation is normal. It is mainly reflected in the service life of the bag of the dust collector and the resistance of the equipment during operation. Sometimes, if the filter bag is damaged and the The high resistance when the equipment is running has a lot to do with it. The correct design of the structure and accessories is an important part of the successful operation of the bag filter.
Qualification with high resistance: Bag type dust collector is a kind of dust removal and purification equipment that can filter dust-containing gas with filter material. It has the characteristics of high dust removal efficiency, simple structure, strong adaptability and stable operation. It is widely used in metallurgy and thermal power generation. , Cement manufacturing and other industries. However, during the production process, equipment running resistance is often high, resulting in reduced dust removal efficiency and shortened filter bag life. When the operating resistance of a bag filter exceeds 1500Pa, we can say qualitatively that the operating resistance of this filter is higher. When the running resistance of the dust collector exceeds 2000Pa, it will have a greater impact on the ventilation of the entire system.
Reasons for the high resistance: The running resistance of the dust collector is caused by the body, the filter bag, and the dust absorbed on the filter bag. Structural design differences, filter material, filter wind speed, gas dust concentration, dust particle size, gas humidity and other factors have a greater impact on the resistance of the dust collector. The influence of structural design on the resistance of the dust collector The structural design includes the cross section of the inlet and outlet air ducts, the air equalization device of the large bag dust collector, the cross-sectional dimensions of various parts through which the air flows, and the design of air lock, maintenance door seal, and equipment insulation. Improper structural design will make the equipment running resistance high. Reasonable structural design has a body resistance of about 400Pa. The wind speed of the inlet and outlet branch pipes of each bag room should be less than 10m / s, which is conducive to equalizing the wind and reducing the resistance.
Dust concentration: When the dust concentration is too high, the probability of collision between particles increases, causing the particles to stick together, which will also affect the running resistance of the dust collector. At the same time, an increase in concentration means that the thickness of the dust attached to the unit area of the filter bag in a unit time will increase, and the pressure loss generated will also increase. In this case, the equipment often works normally by increasing the cleaning frequency, but this will increase the frequency of filter bag expansion, increase friction between the filter bag and the bag cage, reduce the life of the filter bag, and filter failure. The failure of filter material will in turn increase the pressure loss of the filter bag and increase the resistance of the equipment. In addition, the positive pressure gas blown back during ash cleaning is also one of the reasons for the high resistance of the bag type dust collector. Frequent injection of positive pressure gas into the bag chamber will definitely increase the equipment's operating resistance. Therefore, when the dust concentration is too high, an air blocking device should be added in the air intake duct and ash hopper to perform pre-dust collection to reduce the load on the filter bag and reduce the resistance of the equipment.
Dust particle size: The main impact of dust particle size on the bag filter is the pressure loss and equipment wear. What has a great impact on pressure loss is fine dust, which can block the filtration gap, reduce the permeability of the filter material, and increase the resistance. It is generally believed that needle-like crystal particles and flake-like particles are liable to block the filter cloth, reduce the dust removal efficiency, and increase the running resistance. For fine particles of dust-containing gas, coated filter bags should be used, such as cement kiln tails and slag grinding systems.
The gas often contains a small amount of water vapor. When the relative humidity is between 30% and 80%, it is a general state. When it exceeds this range, it is a high humidity state. When the gas in the dust collector is in a high humidity state, dew condensation occurs under the effect of external cold air, which causes dust to stick and block the filter bag, which reduces the dust collection ability of the filter material and makes cleaning difficult. Increase. For dew condensation, generally choose a filter with a smooth surface, such as a film filter. In addition, do a good job in thermal insulation of the equipment and increase the inlet temperature of the dust-containing gas, which can reduce the negative effects of cold air and prevent the occurrence of condensation. Such as cement kiln tail and slag grinding system. In addition to the external thermal insulation of the bag filter, the equipment maintenance door can not be ignored.
In general, the pressure loss of the clean filter cloth is relatively small and the air permeability is relatively high. In work, its small pressure loss means that its pores are relatively large, and the dust is easy to penetrate. Generally, the dust capture performance is relatively low. In addition, the pressure loss of the dust layer on the surface of the filter bag is one of the factors affecting the pressure loss of the filter bag, and it is related to whether the pores of the filter cloth are blocked. Therefore, the filter cloth is required to have the characteristics that the pores are not easily blocked, the dust collection efficiency is high, the pressure loss is small, the dust cleaning performance is good, and the life is long. Filtering wind speed is an important technical parameter of bag dust collector. When the ash cleaning method, filter material and soot characteristics are different, the designed filtering wind speed should also be different, so the filtering resistance produced is also different.