Air filter cylinder as an important air purification equipment, its working principle mainly includes the following aspects:
1. Filtration stage
1. ** Intake and initial contact **
- When air containing impurities (such as dust, dust, some small particles, etc.) enters the air intake of the air filter cartridge, the air will first contact the filter surface of the filter cartridge. The filter cartridge is provided with a filter screen, the main function of the filter screen is to preliminarily intercept particles in the air. For example, in some large industrial air filtration systems, the air enters the filter cartridge at a certain speed, and the larger dust particles are directly blocked by the filter screen due to gravity and inertia, while the smaller particles continue to flow inside the filter cartridge.
2. ** Deep filter **
- For those smaller particles that pass through the preliminary filter, the filter material inside the air filter cartridge plays a key role. Filters are usually made of fibrous materials, and many tiny pores are formed between these fibers. When air carries particles through these pores, several things can happen:
- ** Screening effect ** : If the diameter of the particles is greater than the diameter of the pores of the filter material, the particles will be blocked on the surface of the filter material and cannot pass through the pores. Just like sifting flour through a sieve, large particles (such as some larger dust clumps) are left on one side of the filter.
- ** Inertial collision ** : When the air flow changes direction in the pores of the filter material, the particles, due to their own inertia, have no time to follow the air to change direction, and will collide with the filter fiber and be adsorbed on the fiber. For example, in the case of fast air flow, the heavier particles are easy to escape the airflow path because of inertia, and hit the fiber.
- ** Interception action ** : For some very small particles, in the process of air flow, they will directly contact with the filter fiber, due to factors such as intermolecular gravity, intercepted by the fiber and adhere to the fiber surface. For example, some small bacteria, virus particles (if the air filter cylinder is used for filtering in a special environment) and so on are intercepted by the fiber.
- ** Electrostatic adsorption (some filter cartridges) ** : Some air filter cartridges are specially treated with static electricity. When the air passes with particles, the charged particles are attracted by the electric field generated by the filter material, thus attaching to the filter material. This method is very effective for capturing small particles (such as PM2.5, etc.) and can greatly improve the filtration efficiency.
2, cleaning stage (to ensure that the filter cylinder continues to work normally)
1. ** Differential pressure monitoring and judgment **
- During the operation of the air filter cartridge, the pressure difference inside and outside the filter cartridge is monitored by the pressure difference sensor installed at the inlet and outlet of the filter cartridge. With the progress of filtration, the particles outside the filter cartridge continue to accumulate, which will gradually increase the resistance of the filter cartridge, resulting in a larger pressure difference between the import and export. When the pressure difference reaches the set maximum, it indicates that the particles on the surface of the filter cartridge have accumulated to a certain extent and need to be cleaned. For example, in the air filter cylinder of some small air compressors, when the pressure difference reaches a certain value (such as 0.1-0.2MPa), the control system will trigger the ash cleaning procedure.
2. ** Cleaning method **
- ** Pulse jet cleaning (common method) **
- When cleaning is required, the compressed air stored in the air bag is released instantly. This compressed air is sprayed into the inside of the filter barrel at a very high speed through a small hole in the nozzle. The jet stream causes the filter to expand and deform instantaneously, like a balloon being suddenly inflated. The strong vibration and backflow generated by this expansion will shake off particles attached to the surface of the filter cartridge. The shaken particles will fall into the ash hopper under gravity. For example, in some air filter cartridges used in pulse bag dust remover, pulse spray ash cleaning can effectively remove dust on the surface of the filter cartridge and restore the filtration performance of the filter cartridge.
- ** Mechanical vibration cleaning **
- Vibrate the air filter cartridge through an external mechanical vibration device (such as a vibration motor). This vibration can cause particles attached to the surface of the filter to loosen and fall off. However, for some particles with large viscosity or particularly small particle size, the ash cleaning effect may not be as good as pulse jet cleaning. In some small air purification equipment, this relatively simple cleaning method may be used.
- ** Reverse blow clean ash **
- Use the reverse air flow generated by the fan to blow from the inside of the filter cylinder to the outside. The reverse airflow can blow off particles attached to the surface of the filter cartridge, causing them to fall into the ash hopper. This method is suitable for cases where the filter cartridge is long or the cleaning requirement is high. For example, in some large industrial ventilation systems in the air filter cylinder, the reverse air cleaning can more evenly remove the particles in all parts of the filter cylinder.
Through the alternating work of the two main stages of filtration and ash cleaning, the air filter can continuously remove impurities in the air, ensure the cleanliness of the air, and provide clean air for various industrial equipment and the environment.