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

Views:5     Author:Site Editor     Publish Time: 2020-12-01      Origin:Site

Filtration efficiency affects the choice of purchased products and later production efficiency and the environment, so it affectsair filterWhat are the factors of filtration efficiency? Wells Purification tells you!

1. Filter bag material

The selection and application of filter bag materials is the core technology of bag-type dust collection equipment, which plays a decisive role in the performance of high-efficiency air filter dust collectors. Due to the environment of each dust collection point, the nature, temperature, and technical requirements of the dust to be handled are different, different filter 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 properties: filter bag materials are suitable for different temperatures, good peelability, easy to clean dust, good air permeability, low resistance, high filtration efficiency, high strength, can withstand high-intensity cleaning, use Long life and reasonable price.

2. Filter wind speed

Wind speed increases and resistance increases, while wind speed decreases and resistance decreases. For large particles dominated by inertial motion, the wind speed increases, the inertia of the particles increases, and the possibility of hitting obstacles increases, so the filtration efficiency is improved. However, the inertia increases, and the rebound force of the obstacle to the particles increases. If the van der Waals force cannot overcome the rebound force, the particles will run away. Therefore, sometimes the wind speed is increased, and the filter efficiency of the filter for large particles decreases.

For small particles dominated by diffusion movement, the filtration efficiency depends on the retention time of the particles in the filter medium. The retention time is shortened (increased wind speed), the probability of particles hitting obstacles is reduced, and the filtration efficiency is lower. 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, both for large and small particles.

Electrostatic materials are very sensitive to the filtering wind speed. For example, when measured at a wind speed of 1 cm/s, the permeability of 0.3 μm dust is 0.01% (filtration efficiency 99.99%). When the filtration wind speed is increased to 5.3 cm/s, the measured permeability is 1.5% (filter effect

The rate is only 98.5%), the transmittance is two orders of magnitude worse.

3. Humidity

In general, changing the humidity will not affect the efficiency and resistance of the air filter. However, when the air humidity is high, the filter medium may condense, and there is a water film on the contact surface of the particulate matter and the obstacle. The contact surface between the two is larger, the bonding force is also greater, and the large particulate matter no longer rebounds so easily. The filtration efficiency of large particles may be improved.

In reality, if the filter is so wet that it contains water, the performance of the filter may undergo various unexpected changes. For example, for filter paper made of plant fibers, if the water resistance of the paper is not good, the water will soften the paper and the fibers will compress, and the resistance of the filter will increase rapidly until the filter is blocked. For another example, the high-efficiency filter carries water, and the dust will be transported by the water to the leeward side of the material. After air 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%. The bag filter is generally operated under negative pressure, such as air leakage, it is easy to form a small circuit short circuit. The dust collection system does not handle enough air volume, resulting in positive pressure dust. Air leakage will also reduce the temperature of the system, cause damp and paste bags, increase dust collection resistance, and reduce the filtering effect of air filter equipment.


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