Possibility analysis of high resistance of filter cloth bag dust collector
(1) characterization of high resistance Bag type dust collector is a kind of high-efficiency dust removal and purification equipment that uses filter material to filter dusty gas. It has the characteristics of high dust removal power, simple structure, strong adaptability and stable operation. It is widely used in metallurgy, thermal power generation, cement manufacturing and other industries. However, in the production process, the running resistance of the equipment is often high, resulting in the reduction of the dust removal power and the shortening of the life of the filter cloth bag. When the operating resistance of a bag filter exceeds 1500pa, we can qualitatively say that the operating resistance of this filter is too high. When the operating resistance of the dust collector exceeds 2000Pa, the ventilation of the whole system will be greatly affected.
(2) reasons for high resistance The operation resistance of the dust collector is caused by the body, the filter cloth bag and the dust adsorbed on the filter cloth bag. Factors such as structural design difference, filter material material, filtration wind speed, gas dust concentration, dust particle size and gas humidity have great influence on the operation resistance of the dust collector.
2.1 influence of structure design on the operation resistance of dust collector The structural design includes the section of the inlet and outlet air duct, the air equalizing equipment of the large bag filter, the section dimension of each part through which the air flow passes, and the design of air lock, access door seal, equipment insulation, etc. Unreasonable structural design will lead to high running resistance of the equipment. The proper resistance of the reasonable structural design is about 400pa. The author suggests that the wind speed of the inlet and outlet air ducts should be less than 15m / s, and the wind speed of about 10m / S is the best. The wind speed of the inlet and outlet branch pipes of each bag chamber shall be less than 10m / s, which is conducive to both wind equalization and resistance reduction.
2.2 dust concentration When the dust concentration is too high, the collision probability between particles increases, making particles adhere together, which will also have a certain impact on the operating resistance of the dust collector. At the same time, the increase of the concentration also means that the thickness of the dust attached to the filter bag per unit area in the unit time will increase, and the pressure loss will also increase. Under this condition, the equipment often works normally by improving the ash removal frequency, but this will increase the frequency of expansion of the filter cloth bag, increase the friction between the filter cloth bag and the bag cage, reduce the service life of the filter cloth bag and make the filter material ineffective. Failure of filter material will in turn lead to increase of pressure loss of filter cloth bag and improvement of equipment operation resistance. In addition, the positive pressure gas blown back during ash cleaning is also one of the reasons for the significantly high operating resistance of the bag type dust collector. Frequent injection of positive pressure gas into the bag chamber is bound to increase the operating resistance of the equipment. Therefore, when the dust concentration is too high, the material blocking and air equalizing equipment shall be added in the air inlet duct and the ash hopper for pre dust collection treatment to reduce the filter bag load of the dust collector and reduce the equipment resistance.
2.3 particle size of dust The main influence of dust particle size on bag filter is pressure loss and equipment wear. Fine dust has a great impact on pressure loss, which can block the filter space, reduce the permeability of the filter material, and increase the resistance. It is generally believed that needle shaped crystal particles and flake shaped particles simply block the filter cloth, reduce the dust removal power and increase the operation resistance. The dust containing gas with fine particles shall be covered with membrane filter bags, such as cement kiln tail and slag grinding system.
2.4 humidity The gas often contains a small amount of water vapor. When the relative humidity is between 30% and 80%, it is a general condition, and when the scale is exceeded, it is a high humidity condition. When the gas in the dust collector is in a high humidity state, under the effect of external cold air, dew condensation will occur, forming dust binding and blocking the filter bag, so that the dust collection capacity of the filter material decreases, the dust removal is difficult, and the pressure loss of the equipment increases. As for condensation, generally try to select surface lubricating filter materials, such as membrane filter materials. In addition, do a good job of equipment insulation and improve the population temperature of dusty gas, which can reduce the negative effect of cold air and avoid the occurrence of condensation. Such as cement kiln tail and slag grinding system. In addition to external thermal insulation, the equipment access door of bag filter shall not be neglected.