Filtration Principle Of Filter

1. Intercept the dust particles in the air, move with inertial motion or random Brownian motion or move by some field force. When the particle motion hits other objects, the van der Waals force exists between the objects (molecular and molecular, The force between the molecular group and the molecular group causes the particles to stick to the surface of the fiber. The dust entering the filter medium has a greater chance of hitting the medium, and it will stick when it hits the medium. The smaller dust collides with each other to form larger particles and settle, and the particle concentration of the dust in the air is relatively stable. The fading of the interior and walls is for this reason. It is wrong to treat the fiber filter like a sieve.

2. Inertia and Diffusion Particle dust moves in inertia in the airflow. When encountering disorderly fibers, the airflow changes direction, and the particles are bound by the inertia, which hits the fiber and is bonded. The larger the particle, the easier it is to impact, and the better the effect. Small particle dust is used for random Brownian motion. The smaller the particles, the more intense the irregular movements, the more chances of hitting the obstacles and the better the filtering effect. Particles smaller than 0.1 micron in the air are mainly used for Brownian motion, and the particles are small and the filtering effect is good. Particles larger than 0.3 microns are mainly used for inertial motion, and the larger the particles, the higher the efficiency. It is not obvious that the diffusion and inertia are the most difficult to filter out. When measuring the performance of high-efficiency filters, it is often specified to measure the dust efficiency values that are the most difficult to measure.

3. Electrostatic action For some reason, fibers and particles may be charged with an electrostatic effect. The filtering effect of the electrostatically charged filter material can be significantly improved. Cause: Static electricity causes the dust to change its trajectory and hit an obstacle. Static electricity makes the dust stick more firmly on the medium. Materials that can carry static electricity for a long time are also called “electret” materials. The resistance of the material after static electricity is unchanged, and the filtration effect is obviously improved. Static electricity does not play a decisive role in the filtration effect, but only plays an auxiliary role.

4. Chemical filtration Chemical filters mainly selectively adsorb harmful gas molecules. There are a large number of invisible micropores in the activated carbon material, which have a large adsorption area. In the activated carbon of rice grain size, the area inside the micropores is more than ten square meters. After the free molecules are in contact with the activated carbon, they condense into a liquid in the micropores and remain in the micropores due to the capillary principle, and some are integrated with the material. Adsorption without a significant chemical reaction is called physical adsorption. Some of the activated carbon is treated, and the adsorbed particles react with the material to form a solid substance or a harmless gas, which is called a Huai adsorption. The adsorption capacity of the activated carbon during the use of the material is continuously weakened, and when it is weakened to a certain extent, the filter will be scrapped. If it is only physical adsorption, the activated carbon may be regenerated by heating or steaming to remove harmful gases from the activated carbon.

Post time: May-09-2019