The performance of various cleaning methods of dust bag filter

Dust bag dust collector relies on the dust filter bag to filter the dust containing gas. When dusty gases pass through the dust removal filter bag, as they go deep inside the filter material, the gap between them gradually decreases, and finally forms a dust layer attached to the surface of the filter bag, namely the so-called primary layer. The filter function of cloth bag filter is mainly based on the initial layer and the gradually accumulated dust layer. Even if the filter is very fine dust, it can obtain higher dust removal efficiency. With the continuous accumulation of dust on the basis of the initial layer, the air permeability becomes worse and the resistance of the dust collector increases. Although the dust removal efficiency of the filter bag is also increased at this time, too much resistance makes the filter bag easily damaged or the pressure difference between the two sides of the filter bag is too large, so that the air passing through the hole of the filter bag is too high (filtration speed) and the adhered dust is taken away, but the dust removal efficiency decreases. Therefore, the bag dust collector should be cleaned in time after running for a certain time, and the initial layer should not be destroyed when cleaning, so as not to reduce the dust removal efficiency.

There are three kinds of dust removal methods of cloth bag dust collector: mechanical shaking dust removal, reverse air blowing, pulse jet dust removal.

First, mechanical shaking dust removal. Mechanical vibration cleaning uses mechanical devices, including manual, electromagnetic and pneumatic vibration, to make the filter bag vibrate at a frequency ranging from a few to several hundred times per second.

Mechanical shaking is to close the dust removal fan first, and then through the reciprocating shaking of a shaking motor to the filter bag a reciprocating force in the axis direction, the filter bag will convert the reciprocating force into a radial jitter motion, so that the dust attached to the filter bag falls down. Obviously, in the filtering state, because the filter bag is columnar under the pressure of the air flow, the reciprocating motion of the shaking shaft cannot be converted into the radial jitter of the filter bag, which is why the machine must be shut down for cleaning. In order to make full use of the filtration effect of the dust layer, the filtration speed is low and the cleaning time interval is long (when the resistance reaches 400-600Pa, the cleaning is appropriate). Even if the ordinary cotton cloth is used as the filter material, the dust removal efficiency will be higher. The dust collector with this method has the advantages of simple structure and stable performance. It is suitable for the dust removal of small air volume, low concentration and scattered dust points, but it is not suitable for the occasions where the dust collector works continuously for a long time.

Two, reverse air blowing back ash

(1) The separation chamber and reverse blowing method adopts the separation chamber structure, the valve is switched room by room, and the reverse air flow is formed, which forces the dust bag to shrink or swell and remove dust. This cleaning method also belongs to the low kinetic energy type, with the help of the working pressure of the bag dust collector as the cleaning power, only in special occasions with the reverse blowing airflow power.

(2) The bag-type dust collector with vibration back blowing and reverse air flow dual dedusting function has the vibration to loosen the dust cake and the reverse air flow to make the dust out. The two methods cooperate with each other, so that the cleaning effect can be improved, especially suitable for fine particles of viscous dust filtration. The filter material selection of this kind of bag type dust removal is basically the same as the bag type dust collector with the chamber back blowing method.

(3) High-pressure fan or blower is used as the power of reverse blowing. Strong reverse air flow is formed by moving the nozzle to spray the filter bag successively, which makes the filter bag rapidly deform and clean the dust. It is a type of medium energy dust cleaning. According to the nozzle form and its moving track, it can be divided into three types: rotary blowback, reciprocating blowback and gas ring sliding blowback.

(4) The bag-type dust remover of rotary and reciprocating back-blowing type adopts the form of external filter flat bag with dust skeleton, which has a compact structure. Air is blown back from the opposite direction through the filter bag and the dust layer, using the air flow to make the dust fall off the filter bag. When air flow is used, the filter bag must have a supporting structure, such as a ring or a mesh frame, to avoid flattening the filter bag, adhesion, damage to the initial layer.

Three, pulse spray dust. The pulsed jet cleaning method uses compressed air as the power, uses the pulse jet mechanism to release compressed air instantaneously, and induces several times of secondary air to shoot into the filter bag at high speed, which makes the filter bag expand rapidly, and relies on impact vibration and reverse gas to clean the dust, which is a type of high kinetic energy cleaning.) When the dusty gas passes through the filter bag, the dust stays on the outer surface of the filter bag, and the purified gas is discharged from the upper part through the dome pipe.

The principle of pulse dedusting is that the inflating effect of the jet air will inflate the filter bag from the filtering state to the center contraction outward deformation and vibration, resulting in the dust layer on the outer surface of the filter bag to break. At the same time, the pulse air makes the air inside the bag vibrate, driving the micro-vibration of the filter bag. Coupled with the reverse blowing effect of the jet air and the ejection air, the process of dust leaving the filter bag surface is realized, and the purpose of dedusting is achieved.