2024-02-05
Air filter is a commonly used equipment in industrial dust removal. Its function is to filter out dust, dust and other pollutants in the air through filtration technology.
However, different air filters have differences in filtration efficiency, and there are many factors that cause these differences.
The selection and application of filter bag and filter cartridge materials are the core technology of dust removal equipment and play a decisive role in the performance of high-efficiency air filters.
Since the environment of each dust collection point is different, the nature, temperature and technical requirements of the dust being processed are also different. Therefore, different filter materials should be selected under different conditions and corresponding technical protective measures should be taken.
The requirements for filter bag materials include the following technical properties:
Wind speed increases and drag increases, while wind speed decreases and drag decreases. For large particles that mainly move by inertia, the wind speed increases, the inertia of the particles increases, and the possibility of encountering obstacles increases, thus improving the filtration efficiency.
However, the inertia increases and the obstacle's repulsive force on the particles increases. If the van der Waals forces cannot overcome the rebound force, the particles will escape. Therefore, sometimes the wind speed increases and the filtration efficiency of the filter for large particles decreases.
For small particles whose movement is dominated by diffusion, the filtration efficiency depends on the residence time of the particles in the filter medium. Retention time is shortened (wind speed is increased), particles are less likely to hit obstacles, and filtration efficiency is reduced. If the material is electrostatically charged, the filtration efficiency depends on the residence time of the airflow in the material. The lower the filtration wind speed, the higher the filtration efficiency is for both large and small particles.
Electrostatic materials are very sensitive to filter wind speed. For example, when measured at a wind speed of 1 cm/s, the penetration rate of 0.3μm dust is 0.01% (filtration efficiency is 99.99%). When the filtration wind speed was increased to 5.3 cm/s, the measured permeability was 1.5% (the efficiency of the filter was only 98.5%), and the transmittance was two orders of magnitude worse.
Generally, changing humidity does not affect air filter efficiency and resistance. However, when air humidity is high, the filter media will condense and a water film will exist on the contact surface between particles and obstacles.
The contact surface between the two is larger and the bonding force is greater, so large particles are no longer so easy to rebound. It can improve the filtration efficiency of large particles.
Air leakage directly affects the dust collection effect and the service life of the dust collector, and the air leakage rate is required to be <3%.
Bag dust collectors generally work under negative pressure, such as air leakage, which can easily cause a small circuit short circuit. The dust collection system cannot handle sufficient air volume, resulting in positive pressure dust.
Air leakage will also lower the system temperature, cause moisture and stick the bag, increase dust collection resistance, and reduce the filtration effect of the air filter equipment.
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