Performance and characteristics of the filter cartridge filter
1.1 Composition of the filter cartridge filter
Filter cartridge dust collector mainly has three parts, box body, filter cartridge and ash cleaning system. (1) The box body is the shell of the whole dust collector, including the gas box and ash bucket. The gas tank is mainly to provide the required dust removal space, which is conducive to the reasonable distribution of flow field, and the ash hopper is to collect filtered materials. (2) The filter cartridge is composed of outer layer, inner layer and middle layer. The inner and outer layers are metal mesh (or hard plastic mesh), and the middle is folded filter material. The filter material used in the filter cartridge is characterized by a layer of ultra-thin fiber of sub-micron scale attached to the general filter material. The fibers on the adhesive layer are arranged very closely with a clearance of 0.12 ~ 0.6 m. Due to the use of intensive folding, the filtration area is greatly increased. The great filter area is the prominent characteristic of the filter cartridge. (3) The ash cleaning system mainly includes a blowpipe, a pulse valve, an air bag, etc. When the surface ash reaches a certain thickness, the filter cartridge shall be cleaned. The dusty air is filtered through the filter barrel and then discharged. When the dust collector resistance reaches the set value of pressure difference or time, the corresponding solenoid valve is controlled by the pressure difference control instrument or time control instrument. The pulse valve in the closed state is opened, and the compressed air is directly sprayed into the center of the filter barrel for pulse ash cleaning.
1.2 Working Principle
Generally speaking, the gas enters from the outside of the filter cartridge. The dust with large particles directly settles into the dust hopper without passing through the filter cartridge due to the action of gravity, or colliding with the side wall of the cartridge under the action of inertia force and settling down along the side wall. Small particles of dust pass through the cylinder with the airflow, dust particles in the gas are filtered on the surface of the filter material, and clean gas is discharged from the outlet. Dust in the surface of the filter cartridge is piling up, the resistance is becoming more and more big, achieve value or set a time, pulse valve is opened, compressed gas will blow to filter cylinder center, at the same time, induced air will also strengthen effect of instantaneous high pressure gas filter cylinder surface dust blown away, according to the set of suitable for pulse wave sootblower in turn, make the system restore running low resistance.
1.3 Filtration mechanism
The filtering mechanism of filter materials mainly includes: interception effect, gravity effect, inertia effect, diffusion effect, electrostatic effect, etc. Interception effect: The arrangement inside the filter material is intricate and interleaving. The average aperture of the filter material is small, and the particles whose diameter is larger than the aperture of the filter material cannot be intercepted through the clearance of the filter material layer. Gravity effect: the large particle dust has a high gravity and may settle directly without filter material, or the particles attached to filter material will be separated from the filter material after vibration due to agglomeration and increased gravity. Inertia effect: powder particles move with the airflow, and the airflow circumcircles when it meets obstacles. Dust is collected because the inertia deviates from the direction of the airflow and hits the filter material layer. The larger the particles are, the stronger the inertia force is, and the greater the probability of being filtered down is. Diffusion and electrostatic effect: fine dust collides with the filter material layer, and the gravitation between dust and the surface of the filter material makes it stick to the filter material and be filtered down. The particles with smaller particle size should do Brownian motion, collide with each other, collide with the small particle size or friction charge with the filter material, and the particles are attracted and collected. The large particle dust is mainly used by the first several filtration mechanisms, while the smaller particle size is mainly used by the latter several. A variety of filtration mechanisms at the same time, so that most of the dust will be filtered down, dust remover efficiency will be higher.
1.4 Technical Features
Compared with bag filter, cartridge filter has the following characteristics :(1) high dust removal efficiency. The efficiency of dust removal is 99.99% for general micron scale, and can be achieved or even higher for some highly capable filters (such as The Donaldson ultra-Web filters) for dust size of 0.5 m. (2) Low resistance. For ordinary powders, the drag force of the filter cartridge dust collector is less than 1000Pa, and the adhesion force of the powder is stronger, generally the maximum resistance is about 1500Pa. (3) Wide range of inlet concentration. The ordinary polyester filter cartridge or folding filter cartridge can handle the airflow with high dust concentration at the inlet, and the dust concentration at the inlet can reach 250g/m3. (4) Wide filtering wind speed range. Different material filter cartridge filter wind speed is different. Generally, the filter wind speed of bag filter is around 1m/min, while the filter wind speed of paper filter cartridge is at least 0.3m/min, and that of folding filter cartridge is at most 2.4m/min. (5) Washing performance. In addition to paper filter materials, other filter tubes such as polyester filter tubes and coated filter tubes can generally be cleaned with water, and can be reused after drying; (6) Relatively compact layout, saving space, easy to maintain.