The optimal resistance of a bag filter should be the result of considering factors such as equipment cost, operating cost, filter bag lifespan, and dust removal rate. However, it is not easy to calculate the optimal resistance of a cloth bag dust collector, as its resistance is not only related to factors such as filtration speed, dust load, and the air permeability of the cleaning fabric that are relatively easy to determine, but also to the surface condition of the fabric, the characteristics of dust particles, the temperature and humidity of the gas, the structure of the dust collector, and the cleaning method. Therefore, the optimal operating resistance of cloth bag dust collectors is usually determined based on practical experience obtained from treating similar gases and dust with similar fabrics.
Generally, in the first few filtration cycles after using clean fabrics, the amount of deposited dust removed by cleaning is relatively high, and it gradually decreases in the future. After a period of time, the remaining dust after cleaning reaches a roughly constant value. At this point, the remaining dust deposited on the fabric is basically saturated. Afterwards, the pressure drop cycle for filtering and cleaning will be relatively stable. If the adhesion of dust is strong and there is still no balance of residual dust after my filtration and cleaning cycle, the residual pressure drop may rise to an unacceptable level. In this case, it is necessary to strengthen dust cleaning or replace or clean the filter bag according to the length of use.
Dust cleaning has an impact on the dust removal efficiency of cloth bag dust collectors. According to experimental research on cloth bag dust collectors, during one filtration cycle of the filter bag, the amount of dust that leaks out of the filter bag after just cleaning is the most. After about 4 minutes, the thickness of the dust deposited on the filter bag increases to a certain degree, and the amount of leaked dust decreases and remains at an almost constant low level. After just cleaning the dust, there is a lot of dust leakage because when the spraying stops, the filter bag that was originally bulging due to the spraying retracts and collides with the keel, coupled with the filtering effect of the airflow, causing the dust to pass through the fabric and overflow. If the filtering speed is increased, this dust leakage phenomenon will worsen. This is because increasing the speed will increase the amount of dust that does not fall into the ash hopper after cleaning and returns to the filter bag, while the airflow passing through a thicker dust layer at a higher speed will cause a higher pressure drop, resulting in a strong collision between the fabric and the keel.
Bag filter, also known as filter type dust collector, is a dust removal device that uses bag shaped filter elements made of fiber woven fabric to capture solid particles in dusty gases. It has the following characteristics:
(1) Dust removal, generally above, can achieve a dust concentration of 20-30mg/1113 in the gas at the outlet of the dust collector;
(2) It has a large range of volume and can handle very dusty gases, so it can be used as a magic turbidity device for various dusty gases. Its capacity can range from a few cubic meters per minute to tens of thousands of cubic meters per minute of airflow. When using synthetic fiber filter bags and pulse backwash cleaning methods, it can handle dust containing gases with dust concentrations exceeding 700000 mg/m3. It can be used for ventilation and dust removal of dust sources, air quality in workplaces, as well as for flue gas dust removal of industrial boilers, fluidized bed boilers, kilns, and cake power plant boilers. It can also be used for dust removal of barrier gases in various processes such as cement, carbon black, asphalt, lime, gypsum, and fertilizers to reduce the emission of dust pollutants;
(3) The structure is relatively simple and easy to operate and maintain;
(4) Under the same dust removal efficiency, its cost and operating expenses are lower than those of electrostatic precipitators;
(5) When using glass fiber and certain types of synthetic fibers to make filter bags, they can operate stably at temperatures between 160-200 ℃;
(6) When selecting filter media, some can withstand temperatures up to 260 ℃;
(7) Not sensitive to the characteristics of dust and not affected by the specific resistance of dust;
(8) When used in dry desulfurization systems, the desulfurization efficiency can be appropriately improved.
