Basic principles and basic knowledge of air filter paper

Time:2020-05-28 Source:Huarui

Many people do not know what the principle of air filter paper is. Why is the dust in the air filtered and purified by equipment such as filter cotton and filters? Let me explain the basic knowledge of air filtration.
   Air filter paper is a purification process in which dust substances in the air are subjected to a certain force, and a relatively porous body is used to remove dispersed dust particles from the gas. The kind of force mentioned above refers to three kinds of inertial force, van der Waals force, and electrostatic force. Large particles move inertially in the airflow, the airflow circumvents the obstacle, the particles deviate from the direction of the airflow and hit the obstacle due to inertia Filter material, so the filtering effect is good. Small particles move irregularly, although they have a certain direction, but mainly do diffusion movement. Because the filter material fibers are fine, the van der Waals force between the two micromolecules makes them stick together, so the dust cannot pass through the filter material, and the filtration effect is good . When we put the filter material on and maintain the electrostatic effect, because the static electricity can retain the dust, the dust cannot pass through the filter material, and the filtering effect is good.
   During air filtration, due to the effects of inertial collision, interception, diffusion and static electricity, the dust particles suspended in the gas sink to the porous material. The structure is fibrous, porous, or a combination of these structures. Collectively referred to as filter materials. The filter material not only effectively intercepts the dust particles, but also does not form excessive resistance to the air flow. The air filter cotton and air filter paper meet this requirement. The messy interwoven fibers form countless barriers to particles, and the wide space between the fibers allows the air flow to pass smoothly.
The moving airflow hits the filter material, and the fiber circulates the airflow, and at the same time produces a small resistance. The resistance of the countless fibers is the resistance of the filter. The resistance of the filter increases with the increase of air flow. By increasing the area of ​​the filter material, the relative wind speed through the filter material can be reduced to reduce the resistance of the filter. The filter forms resistance to the airflow, the filter deposits dust, and the resistance increases. When the resistance increases to a certain specified value, the filter is scrapped. The resistance of the new filter is called "initial resistance"; the resistance value corresponding to the scrap of the filter is called "final resistance".
The captured dust creates additional resistance to the air flow, so the resistance of the filter in use gradually increases. The captured dust forms a new obstacle, so the filtration efficiency is slightly improved. Most of the captured dust collects on the windward side of the filter material. The larger the filter material area, the more dust it can hold, and the longer the filter life. The more dust accumulates on the filter material, the greater the resistance. When the resistance is too large as the design does not allow, the life of the filter will end. Sometimes, excessive resistance will cause the dust that has been caught on the filter to fly away. When this danger occurs, the filter should also be scrapped. According to the above principle, in the process of manufacturing air filters, it is necessary to select excellent filter materials to meet people's need to maintain a fresh space after air filtration. This is the filtering principle we often mention.

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