Introduction of ZJN Equipment Series- Bag House Filter (2)

[Editor’s note] Bag house filter is a kind of dry-type dust filtering device. It is suitable for collecting fine, dry and non-fibrous dust. Filter bag is made of woven filter cloth or non-woven felt, using the filtration of fibre fabric to filter the dusty gas.

When the dust-containing gas enters the bag filter, dust with large particles and large specific gravity settles down under the action of gravity and falls into the ash hopper. When the gas containing relatively fine dust passes through the filter material, the dust is retained and the gas is purified.

The structure of the bag-type dust remover mainly consists of an upper box body, a middle box body, a lower box body (ash hopper), an ash cleaning system, an ash discharging device and other parts. Compared with similar products, the dust removal efficiency has high efficiency of dust removing which is generally above 99%. It has a wide range of air volume handling, and can be used for dust removal of flue gas of various industrial furnaces and drying equipment to reduce the emission of air pollutants; It has the advantages of simple structure, low cost, convenient maintenance and operation, etc.

At present, the bag dust remover has been used as the main matching product of the ZJN drying series equipment in combination with ZJN "Rotary Rake rolling Triple Pass Multi-loop" high humidity and high viscosity material drying equipment, which has good dust removal effects and considerable economic benefits. It has become the first choice for many cooperative customers! This text introduces a main ash removal method of bag house filter--pulse injection ash-cleaning.

The main ash removal method of bag house filter--pulse injection ash-cleaning. A perforated plate (flower plate) for fixing filter bags is arranged at the upper part of the dust collector box body. There is an injection pipe above each row of filter bags, a compressed air injection hole (nozzle) is opened towards the center of each filter bag on the injection pipe, and the other end of the injection pipe is connected with the pulse control system (consists of a pulse valve, a control valve, etc) and compress air storage tank. And then pulse injection and ash removal are carried out according to a specified time or resistance value and on basis of an automatic control program.

The filter bag adopts an external filtration type, and the inner side is provided with a supporting framework, and dust is deposited on the inner surface of the filter bag. At the moment of ash removal, when the high-speed jet air flows through the top of the filter bag, it can induce air several times of the jet air volume to inject into the filter bag together to form a air waves, which causes the filter bag to generate rapid expansion and impact vibration from top to bottom, and generates strong air flow to remove the dust. Generally, the pulse period can be adjusted from 1 minute to several minutes.

According to the flow direction of the pulse jet flow and the purified flow, there are three injection modes: forward jet type, reverse jet type and opposite jet type. The forward jet type means that the two airflow directions are the same, and the cleaned air is discharged from the bottom of the filter bag. The opposite type actually divides the filter bag into two parts: half are opposite-jet and the other are forward-jet.

During injection, the filter bags to be cleaned do not have dust catching effect. Because the injection time is very short and the filter bags clean dust for the first time row by row, the dust catching operation can almost be regarded as continuous processing, the dust cleaning can be off-line and carried out by adopting a chamber structure, or be on-line and carried out without chamber structure.

The pulse ash cleaning has strong and good effects of ash removal, which can improve the filtering air speed. Its intensity and frequency can be adjusted. The ash removal effect is related to the structure of the venturi atmospheric pressure and the consistency between the centerline of the jet flow and the centerline of the filter bag . When the filter bag is longer, good ash removal effect can also be obtained by using a better injection device.

Due to its strong ash removal effect, it is also effective for viscous felt filter materials. The use of felt filter materials has also begun to spread. Felt filter material can be used for effective filtration as a whole from a microscopic point of view, so its apparent filtration speed can be higher than that of woven cloth, thus making the device miniaturized.

The pulse injection device needs compressed air as energy source. In the cold zone, since the water vapor in the compressed air is easy to condense and affect the injection effect, it is not suitable to be placed outdoors, and corresponding technical measures should be taken to prevent condensation or freezing.

Finally,besides the centralized dust removal methods as described above, there are other ash cleaning methods such as air ring back-blowing, air box pulsing and pulse back-blowing.