Bag filter pulse bag filter waste gas treatment of Guangzhou die casting machine

The bag filter relies on the woven or felt woven (pressed) filter cloth as the filter material
When the dusty gas passes through the filter bag, the dust is blocked on the surface of the filter bag, and the dry air is discharged through the gap between the fibers of the filter bag, so as to achieve the purpose of separating the dusty gas and dust
Its working mechanism is that dust is trapped by screening, inertia, adhesion, diffusion and static electricity when passing through the filter cloth

(1) Screening action
When the dusty gas passes through the filter cloth, the gap between the fibers of the filter cloth or the gap between the dust adsorbed on the surface of the filter cloth separates the dust larger than the gap diameter, which is called screening
For new filter cloth, due to the large gap between fibers, this effect is not obvious and the dust removal efficiency is also low
Only after a certain time of use, a certain thickness of dust layer is set on the surface of the filter bag, the screening effect is more significant
After ash removal, a certain amount of dust remains on the surface and inside of the filter bag, so it can still maintain good dust removal efficiency

For needle punched felt or pile filter cloth, because the felt or pile filter cloth itself forms a thick porous filter layer, it can give full play to the screening function, and does not completely rely on the dust layer to maintain a high dust removal efficiency

(2) Inertial action
When the dusty gas passes through the filter cloth fiber, it is greater than 1μ M dust is still in linear motion due to inertia and is trapped when it strikes the fiber
The larger the diameter of dust particles, the greater the inertia effect
The higher the filtration gas velocity is, the greater the inertia effect is
However, if the gas velocity is too high, the air volume passing through the filter cloth will also increase, and the air flow will break through the weak part of the filter cloth, resulting in the reduction of dust removal efficiency
The higher the gas velocity, the more serious the perforation phenomenon

(3) Diffusion
When the dust particles are 0
2-mu; Below m, the Brownian motion such as the thermal motion of gas molecules is generated due to the extremely small dust, which increases the contact opportunity between the dust and the filter cloth and makes the dust trapped
This diffusion effect is opposite to the inertia effect
It increases with the decrease of filtration gas velocity and dust particle size
Taking glass fiber as an example, the finer the fiber, the higher the dust removal efficiency
However, the pressure loss of fine fiber diameter is greater than that of coarse fiber, and the finer the fiber diameter, the worse the corrosion resistance

(4) Adhesion
When the dusty gas approaches the filter cloth, the fine dust still moves with the air flow
If the radius of the dust is greater than that in the dust
When the distance from the center to the edge of the filter cloth, the powder dust is adhered by the filter cloth and collected
The smaller the gap of the filter cloth, the more significant the adhesion

(5) Electrostatic action
The impact between dust particles will generate static electricity
If the filter cloth is an insulator, it will charge the filter cloth
When the charge of the dust and the filter cloth is opposite, the dust will be adsorbed on the filter cloth, so as to improve the dust removal efficiency and make it difficult to clean the dust
On the contrary, if the charges carried by the two are the same, repulsive force will be generated, and the dust can not be adsorbed on the filter cloth, which will reduce the dust removal efficiency
Therefore, electrostatic effect can improve or hinder dust removal efficiency of the filter cloth
In order to ensure the dust removal efficiency, the filter cloth must be selected according to the charge property of the dust
Generally, the electrostatic effect is only when the dust particle size is less than 1μ M and when the filtration gas velocity is very low
In the case of external electric field, the electrostatic effect can be strengthened and the dust removal efficiency can be improved