During filtration of dust-laden gas, the bag filter removes more dust, so that the passage of the air flow is reduced, the resistance of the filter bag to the air flow gradually increases, and the processing air volume also decreases according to the pressure-air volume characteristics of the ventilation system of the used fan. When the resistance rises to a certain extent, there will be such problems.
1. large power consumption, not economical.
2. The resistance exceeds the maximum value of the ventilation system design. Ventilation cannot meet the need.
3. After the dust accumulates on the filter bag, the porosity becomes smaller, and the speed of air passing through will increase. When it is increased to a certain degree, the dust layer will produce a “pinhole”, so that a large amount of air flows through the pinhole with a small resistance, so that a so-called “leakage” phenomenon is formed, which affects the dust removal effect.
4. too much resistance, filter material is easily damaged. Therefore, during the use of the bag filter, dust must be removed from the filter bag by some dust (even if only from the point of view of collecting dust, the dust collected on the filter bag must be removed to collect ). However, after cleaning, there is still a considerable amount of dust remaining in the pores of the fabric, the residual resistance and time after cleaning, and from the point of view of damage to the fabric, this is not economical, and after cleaning, At the beginning of the next filter cycle, the remaining dust can also play a considerable role in dust collection, so the cleaning does not need to be thorough.
Generally, in the first few filtration cycles after the clean fabric is used, the dust removed by the dust removal is more and less and less. Over a period of time, the remaining dust after cleaning has reached a constant value. At this time, the residual dust deposited on the fabric is almost saturated. After this, the pressure drop cycle of filtration and cleaning is also relatively stable. If the adhesion of dust is strong, there will be no balance of residual dust after my filter-clearing cycle, then the residual pressure drop may rise to an unacceptable level. In this case, it is necessary to intensify the cleaning or replace or clean the filter bag according to the length of time it is used.
Ash removal has an effect on the dust removal effect. According to the results of leith et al.’s experimental research on the pulse bag filter, in the filtration period of the filter bag, the dust that escapes the bag after the fresh cleaning is the most, after about 4 minutes, The thickness of the dust deposited on the filter bag increases to a certain extent, and the leaked dust rapidly decreases and remains at an almost constant low level. Leith et al. believe that after the ash was cleaned, more dust was leaked because the filter bag that had been swelled due to the injection was stopped, collided with the keel, and the effect of the filtered airflow caused the dust to pass through. The fabric overflows, and if the filtration rate increases, this dust leakage will increase. This is because the increase in speed will increase the dust that will not fall into the ash bucket and return to the filter bag after cleaning, and the airflow passing through the thicker dust layer at a higher speed will cause a higher pressure drop, causing the fabric to collide with the keel. powerful. According to another study, compared with mechanical vibration cleaning filter bags, the dust concentration of the pulse cleaning filter bag immediately after cleaning is greater than the former.
Fabrics undergo extensive filtering after a cleaning cycle due to mechanical buckling and relative movement. In addition to the abrasive effect of dust, the fibers are gradually damaged, resulting in breakage, and the fabric is thinner at the point of flexion, so that the dust passing through these places increases. At the end, thin areas or cracks have developed so that they cannot be filled with the collected dust. In this case, the filter bags cannot be used anymore and need to be replaced or repaired.