The main factors affecting the dust collection efficiency and emission concentration of bag filter are dust characteristics, filter characteristics, cleaning methods and filtration speed.
1) The effect of dust characteristics on the efficiency of the bag filter. Such as dust particle size, directly affect the dust collector’s dust removal efficiency and discharge quality concentration. The dedusting efficiency of the filter material under different conditions increases with the increase of particle size. For dust particles of 1.0um or more, the dust removal efficiency can reach 99.5% or more; and for dust particles less than 1.0um, dust removal efficiency of O.2 ~ 0.4um is the lowest. The reason is that in this particle size range, inertial collisions, entrapment, diffusion effects, and dust collection mechanisms are all at low values.
Whether the dust particles are charged or not also affects the dust collection efficiency of the bag filter. The charge of dust particles tends to coagulate the fine dust, and it is easy to absorb the oppositely charged filter material, thereby increasing the dust collection efficiency of the bag filter.
2) The effect of filter characteristics on the efficiency of the bag filter. The size of the pore diameter on the surface of the filter and whether the hole is straight through have a significant effect on the dust removal efficiency and the emission concentration. It can be seen from the above filtering process that the surface area of the woven cloth filter material is large and the hole is straight. During the filtration process, the filter material must be charged with dust and the initial layer of dust must be established in order to improve the dust collection efficiency of the bag filter. In the process of establishing the initial layer of dust and because the dust cleaning is too strong and the initial layer of dust is destroyed, the dust removal efficiency is very low, and the dust emission landscape has a large concentration. For the needle felt filter material, because its surface pore size is small, and it is not straight, the filtration process has little effect on the dust removal efficiency, and the total dust removal efficiency is high. And on the film filter. The surface pore size is smaller, only 0.2-3.Oum (average), nor is it straight. The filtration process has almost no effect on the dust collection efficiency of the bag filter. The total dust removal efficiency is highest and the emission concentration can approach zero.
There are many kinds of filter materials and their characteristics are different. Must be fully familiar with the characteristics of various filter materials, the correct choice in the design, according to the requirements of the filter carefully installed, carefully maintained use, to master the strength of cleaning, do not destroy the initial layer of dust. Otherwise, the dust collection efficiency of the bag filter will be greatly affected and the emission concentration will increase.
3) The effect of cleaning method on the efficiency of bag filter. There are many ways to clear ash, and the intensity of cleaning is also different. The mechanical rapping and the back-blow-off of the chamber are relatively weak in the dust removal, and the nozzles are of the reverse cleaning type, and the pulse cleaning is the strongest. When cleaning ash, it is necessary to master the intensity and time, especially when the pulse is cleaned. Adjust the pressure and time of the ash cleaning so as not to damage the primary layer of dust, so as to reduce the amount of dust emitted when the dust is recovered after cleaning. . Otherwise, the bag filter dust emission concentration will increase.
4) The effect of the filter wind speed on the efficiency of the bag filter. At the beginning of filtration (before the establishment of the initial layer of dust), for the woven fabrics, the small filtration speed helps to establish the initial layer of dust more quickly; when the filtration speed is large, the initial layer of dust is established slowly and the emission concentration is large. The influence on the needle felt filter material is small, and the influence on the film filter material is smaller. The relationship between the accumulation of dust load on the filter material and the change of the dust removal efficiency under different filter wind speeds. From the viewpoint of improving the dust collection efficiency of the bag filter, the low filtration speed is better.
5) The mechanism that affects the dust collection efficiency of the bag filter. According to our research, the mechanism of dust particle dust penetration through the filter media, which results in a drop in the dust collection efficiency of the bag filter, mainly has the following three aspects:
1 Through dust particles smaller than the pore diameter of the surface of the filter or dust layer penetrate the filter material (open pores), or penetrate through the pores in the filter material or in the dust layer (pore does not pass through).
2 In the process of filtration, when the dust layer deposited on the filter material is gradually thickened, the pressure difference of the filter layer is also increased. Under the effect of pressure difference, dust may be bridged on the pores of the filter material. Destruction, dust particles are pressed through the pores. When filtration is resumed after cleaning, the dust particles are pressed through the small layer of locally broken powder.
3 Blowholes When the filter dust velocity of the bag filter is high, the dust particles may penetrate through the pores of the dust layer and flow out with the airflow.
At a high filtration wind speed of 9m/min, due to the rapid increase of the dust layer, the pressure difference of the airflow through the filtering dust layer increases, and the dust dissipated by the stomatal mechanism increases sharply, while the dust that escapes by the direct-pass mechanism rapidly decreases. Regardless of the filter air speed of the bag filter, the direct mechanism plays a major role. The pore mechanism only appears prominently at high filtration wind speeds. The effect of the extrusion mechanism is not obvious in the whole filtration process and the dust escapes. The amount is relatively small.
