Bag filter is a dust removal device widely used in electric power, chemical industry, casting and other industries. In the vertical roller mill production line, it is sometimes found that the efficiency of the bag filter is not as high as theoretically. So how to improve the dust removal efficiency of the bag filter?
First choose the appropriate dust bag. The selection of the dust bag is crucial, directly affecting the dust removal effect of the dust collector. The dust bag should be selected to take into account the temperature, humidity and chemical properties of the gas, particle size, dust concentration, filtration wind speed, dust cleaning method and other factors. In the vertical mill production line, in the pulse and air box type pulse dust collector, the dust adheres to the outer surface of the bag. When the dust-laden gas passes through the dust collector, the dust is trapped on the outer surface of the filter bag, and the clean gas passes through the filter material and enters the inside of the filter bag. The cage inside the bag is used to support the filter bag to prevent the filter bag from collapsing, and it helps to remove and redistribute the dust cake.
The fabric and design of the high temperature dust-removing cloth bag should be as efficient as possible for efficient filtration, easy dust removal and durability. The glass fiber woven fabric is used as the base fabric, and the high-quality polyester staple fiber is used as the surface layer to make it have high breaking strength, small elongation at break, small heat shrinkage rate and moderate temperature resistance.
Then, after the resistance of the bag filter in the vertical mill production line reaches a certain value, it should be cleaned in time. Generally, the dust removal efficiency of the new filter material is not high enough. After the filter material is used for a period of time, due to the effects of sieve filtration, collision, retention, diffusion, static electricity, etc., the surface of the filter bag is covered with a layer of dust. This layer of dust is called the primary layer. During the subsequent movement, the initial layer becomes The main filter layer of the filter material can rely on the action of the primary layer, and the filter material with larger mesh size can also obtain higher filtration efficiency. As the dust accumulates on the surface of the filter material, the efficiency and resistance of the bag filter increase accordingly. When the pressure difference between the two sides of the filter material is large, some fine dust particles attached to the filter material are squeezed. To reduce the efficiency of the bag filter. In addition, the excessive resistance of the bag filter will significantly reduce the air volume of the dust removal system. Therefore, after the resistance of the bag filter reaches a certain value, it should be cleaned in time. The initial layer should not be destroyed when cleaning, so as to avoid the efficiency drop.
Secondly, different dust speeds should be adopted for dust of different particle sizes. There are inertial effects in the dust removal process, including collision, interception and diffusion effects. Therefore, when improving the efficiency of the precipitator, dust particle size can be considered: dust with a particle size of 5-15 μm can effectively collect dust by inertia effect, so the filtration wind speed can be increased to improve the dust removal efficiency of the dust collector. . The fine dust having a particle diameter of 1 μm or less can effectively collect the fine dust by the diffusion effect, and thus the purpose of improving the dust removing efficiency of the dust remover can be achieved by appropriately reducing the filtering wind speed.
In addition, the dedusting of the bag filter should be prevented in the vertical mill production line. The dust bag should be used to prevent the gas from cooling below the dew point in the bag, especially when using a bag filter under negative pressure. Because the outer casing often leaks air, the gas temperature in the bag chamber is lower than the dew point, and the filter bag will be damp, so that the dust is not loose, but sticks to the filter bag, blocking the fabric holes and causing cleaning. Failure, the pressure drop of the precipitator is too large to continue to operate, seriously affecting the efficiency of dust removal.
The following measures can be taken to prevent: First, proper warming. For example, if a far-infrared electric heater or an electric heater is installed in the bag filter, or a radiator is added in the bag room, the flue gas temperature of the main machine can be appropriately increased. The second is to reduce air leakage. Leakage of the gap in the body part of the dust collector, the leakage of the bag filter body should be controlled below 3.5%. In the operation and maintenance process, pay special attention to the air leakage of the process equipment in the dust collector system, such as the closed ash discharge valve of the ball mill’s discharge port, the air leakage of the closed ash discharge valve under the dust collector, and the pipe flange connection.