Basic theories of ash cleaning-dust removal principle of bag filter by shaking
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Author : filterworkshop.com
Update time : 2020-02-10 17:46:40
Basic theories of ash cleaning-dust removal principle of bag filter by shaking
dust removal principle of bag filter by shaking
Dust cleaning is an important part and influencing factor of the normal operation of the bag filter. There are three kinds of commonly used cleaning methods, i.e. mechanical cleaning, pulse blowing cleaning and reverse blowing cleaning. For the dust that is difficult to be removed, two methods of ash removal can be used simultaneously, such as the combination of counter blowing and mechanical shake and acoustic assisted ash removal.
Mechanical dust removal refers to the method of using mechanical vibration or shaking the frame of suspension filter bag to make the filter bag vibrate and remove dust. Three common basic shaking modes of mechanical ash cleaning are shown in Figure 1: In Figure 1, (a) is horizontal shaking ash cleaning, with two modes of upper vibration and middle vibration, which are completed by reciprocating motion device; (b) is vertical shaking ash cleaning, which generally uses eccentric wheel device to vibrate the filter bag frame or regularly lift the filter bag frame for ash cleaning; (c) is mechanical torsion ash cleaning, that is, special mechanism is used to regularly twist the filter bag to a certain angle, so that the filter bag is deformed and ash is removed. There are also several ways to combine the above vibration dust removal, the filter bags do up and down, left and right shaking.
In order to improve the effect of mechanical cleaning, vibration is required to stop filtering. However, the small filter can not be stopped, and the dust collector is not divided into chambers. Therefore, it is often necessary to separate the dust collectors into several bag groups or bag chambers, and clean the dust one by one in order to keep the continuous operation of the dust collectors.
The features of mechanical ash cleaning method are simple structure and reliable operation, but the ash cleaning strength is weak, so only low filtering wind speed is allowed, for example, generally 0.6 ~ 1m / min. Excessive vibration intensity will damage the filter bag to a certain extent, increasing the workload of maintenance and bag replacement. This is the reason why mechanical ash removal is gradually replaced by other ash removal methods.
The principle of mechanical dust removal is that the dust and dust mass attached to the filter bag will fall off the filter bag due to the elastic force generated by the shaking of the filter bag. The shaking force is related to the driving device and frame structure. The driving device has large power and small energy loss of frame transmission, so the mechanical ash removal effect is good.
The resistance of the filter cloth with dust is the sum of the resistance of the filter cloth and the residual dust layer. The amount and ratio of these dust residues are determined by the filter cloth, the nature and quantity of the dust, the energy to remove the dust, etc. The relationship between the number of rapping times of rapping mechanism and the amount of residual dust is shown in Figure 2. If the vibration frequency is the same and the vibration amplitude is small, the dust residue is large and the resistance is large.
The dust layer on the filter cloth can be stabilized at a certain value without increasing if the cleaning time is extended. Figure 3 shows the relationship between the vibration time and the amount of dust removed. Figure 4 shows the residual dust distribution on the filter cloth when it vibrates up and down.
