Bag filter reverse suction (blow) wind cleaning operation
The operation of sucking (blowing) cleaning can use “two-state” (reverse suction-bulging), or “three-state” (reverse suction-precipitation-bulging). The process is shown in Figure 6-3.
The time for sucking (blowing) depends on the nature of the dust. The purpose of sucking (blowing) is to make the filter bag loose and shrink, so that the dust is peeled from the filter bag. For this purpose, the reverse suction (blow) time is generally desirable for 10 to 20 seconds, and the reverse suction (blowing) air volume is too large and the time is too long. , Dust filter bag will suck (blow) smashing, in serious cases, even two filter bags close together, hinder the settlement of the upper filter bag dust, while the filter bag overflexion, affect filter bag life.
If there is no supporting skeleton inside the filter bag, the degree of contraction of the filter bag is directly related to the hanging force of the filter bag and the elongation of the filter cloth. Suspension tension is small, the filter bag with a large filter cloth elongation rate is more effective in contraction and sucking, and vice versa. In order to improve the shrinkage of the filter bag during reverse suction (blowing), a hoop may be provided every 1m in the length direction of the filter bag to prevent the filter bag from sucking (blowing).
The swelling time after sucking does not generally need to be too long. The purpose is to create conditions for the next sucking, as long as the dust bag can be bulging, generally taken as 5s. The number of back-suctions is related to the concentration of gas dust. When the dust concentration is low, it is usually 1-2 times for cleaning and dusting, and 3 to 4 times for high dust concentration.
When using the two-state cleaning method, since the filter bag suction time is short (10~20s), the dust that is shaken off from the lower part of the filter bag that is close to the ash bucket can still fall into the ash bucket, and when the length of the filter bag is large The dust falling from the upper part of the filter bag is too late to enter the ash hopper, and the time for sucking is ended, and the filtered airflow that is picked up is brought to the filter bag to generate so-called “re-adsorption”. In order to prevent this phenomenon, a “sedimentation” process may be added between “reverse suction” and “bulging” to form so-called “three-state” cleaning.
There are two types of cleaning procedures for the “three-state cleaning method”:
The first one – focus on natural settlement. This ash removal system is a filter bag that is concentrated for a period of time after it has been cleaned in a two-stage state to allow it to settle naturally. The natural settlement is achieved by closing the air outlet (or air inlet) and the reverse air outlet at the same time, so that no air flow in the filter bag reaches the stationary state of the filter bag, creating a natural sedimentation condition for the shaken dust in the filter bag.
The second type – dispersing natural settlement. This ash-removing system is to arrange a static time between the suction bag and the bulge of the filter bag, so that the dust falling from the inside of the filter bag can settle naturally.
The time required for the natural settlement state is related to the length of the filter bag and the nature of the dust. In general, the high-temperature filter bag is long and the dust density is light, and the natural settlement time is longer.
All kinds of cleaning procedures are realized by the adjustment of the time relay. Through the control of the time relay, it is possible to operate the reverse suction (blowing) air switching valve according to the pre-arranged cleaning procedure to perform reverse suction (blowing) wind cleaning. .
From the above two dust removal systems, it can be seen that after each suction, the dust in the inner side of the filter bag is relatively complete, there is less chance of further accumulation, and the cleaning efficiency is high.
The main features of sub-room suction (blow) bag filter:
(1) The filter bag is not subject to strong friction and flex during operation, and thus has a long service life and is easy to use a glass fiber filter bag.
(2) The compartment structure facilitates maintenance of a compartment without shutting down.
(3) Use system pressure differential (or centrifugal fan) as cleaning power, which is beneficial to use in the absence of air compressor.
(4) Low filtration wind speed, large equipment, and high cost.
(5) The dust-removing intensity is low and the pressure loss is high. The cleaning air flow passes through the main fan, so the operation energy consumption is high.