What are the factors that affect the filtration efficiency of air filters?

Air filter filtration efficiency in the procurement of air filters is the focus of the data, filtration efficiency affects the selection of purchased products and later production efficiency and the environment. Since the filtration efficiency is so important, what are the factors that affect the filtration efficiency of air filters? Here are four factors to analyze for you.
1. Filter bag material:
The selection and application of filter bag material is the core technology of bag dust collection equipment, which plays a decisive role in the performance of high efficiency air filter dust collector. Because of the environment of each dust collection point, the nature, temperature and technical requirements of the dust treatment are not the same, different filtration materials should be selected for different conditions, and corresponding technical protection measures should be taken. The requirements for filter bag materials include the following technical performance: filter bag materials are suitable for different temperatures, good stripping, easy cleaning, good air permeability, low resistance, high filtration efficiency, high strength, can withstand high strength cleaning, long service life, and suitable price.
Second, the impact of filter wind speed:
The wind speed increases the resistance, and the wind speed decreases the resistance. For large particles dominated by inertial motion, the increase in wind speed will increase the inertia of particles and increase the possibility of hitting obstacles, so the filtration efficiency will be improved. However, when the inertia is large, the rebound of the obstacle to the particles also increases. If the van der Waals force cannot overcome the rebound, the particles will run away. Therefore, the filter efficiency of large particles will be reduced when the wind speed is sometimes increased.
For small particles dominated by diffusion movement, the filtration efficiency depends on the retention time of particles in the filtration medium. If the retention time is shortened (the wind speed is increased), the probability of particles hitting obstacles is reduced, and the filtration efficiency is lower. If the material has static electricity, the filtration efficiency depends on the retention time of the air flow in the material. The lower the filtration speed, the higher the filtration efficiency, for both large and small particles.
The electrostatic material is very sensitive to the filtered wind speed. For example, when measured at 1 cm/s wind speed, the transmittance of 0.3 μm dust is 0.01%(filtration efficiency 99.99%), and when the filtration speed is increased to 5.3 cm/s, the transmittance is measured to be 1.5%(filtration efficiency is only 98.5%), which is two orders of magnitude difference in transmittance.
Third, the impact of humidity:
Under normal circumstances, changing the humidity will not affect the efficiency and resistance of the air filter. However, when the air humidity is very high, the filtration medium may dew, the contact surface of the particles and the obstacle has a water film, the contact surface of the two is large, the bonding force is large, and the large particles are no longer so easy to rebound, so the filtration efficiency of the large particles may be improved.
In reality, if the filter is wet to bring water, the performance of the filter may undergo various unpredictable changes. For example, for filter paper made of plant fiber, if the water resistance of the paper is poor, the water makes the paper soft, the fiber compresses, and the resistance of the filter will increase rapidly until the filter is blocked. For example, the high efficiency filter with water, dust will be transported by water to the lee side of the material, after drying, the filter becomes a dust generator.
Four, air leakage
Air leakage directly affects the dust collection effect and life of the dust collector, and the air leakage rate is required to be <3%. Bag type dust collector is generally negative pressure operation, such as air leakage is easy to form a small circuit short circuit. Dust collection system processing air volume is not enough, forming positive pressure dust. Air leakage will also reduce the system temperature, easy to generate moisture paste bag, increase the dust collection resistance, reduce the filter effect of air filter equipment.