Membranes for Air and Gas Filtration

It is easier to remove the particulate matter from the gas streams than liquids due to the additional interaction mechanism between particulates and the Membrane Filter pore surface. The sieve retention mechanism traps particles as the pores are even smaller than the particles themselves. The procedure involves direct interception's gravitational settling and electrical attraction forces in the absorptive capture.

Another secondary mechanism, adsorptive particulate capture, is heightened in the air and gas streams due to inertial impactions and diffusion interceptions. It occurs due to the lower viscosities that develop a minor obstacle to the trajectory of a particle. Consequently, bigger particles entrained in the air or gas stream feature greater inertia and move in a straight course even if the airflow is bending. It is noted in the particles featuring larger mass since their potential of being captured to the solid filter surface is more. Particles that differ in size from 0.3 to 1 µm usually undergo inertial capture, specifically in those high-velocity streams. This situation can impose upon a fiber instead of a pore opening. Once trapped and captured, the particles will not be released back into the air stream.

Alternatively, there will be a possibility of suspending particles in the gas stream due to their small mass. However, those particles can be small enough to come in contact with the surface of a filter.
The low viscosity of a gas stream, like inertial impact, permits suspended particles to be captured through diffusive capture. The high filtering efficiency of air filters is primarily due to this diffusional interception mechanism. The particle capture rate is linearly equal to the square root of the particles.

Because of the wide range of filtration media available, knowing the elements that influence air and gas filter efficiencies can help you make the best choice for your needs. When choosing a material for air and gas filtration, consider four primary material requirements. These include water incursion pressure, differential pressure, airflow rate, and bacterial retention. Oleophobicity, chemical and temperature resistance, and sterilizing procedures may be considered.

When selecting the best Air and Gas Filtration Membranes, we suggest you consider the following essential properties:

Water intrusion pressure

Water incursion pressure is used to validate the pores of a hydrophobic membrane instead of the bubble point test, which is used with hydrophilic membranes. This test is often performed by placing water on one side of the filter and slowly raising the pressure until the water is forced through the filter structure and witnessed coming out the opposite side of the membrane. When selecting a hydrophobic membrane for your application, be sure the pressure it will be exposed to during use does not surpass the specified intrusion pressure. This will ensure that the membrane properly retains liquid droplets from the filtrate.

Pressure gradients

Differential pressure is the difference between the system pressure before the fluid reaches the filtration and the pressure distribution after the liquid flows through the filter. The design phase must be considered when selecting a filter media to guarantee the finished device's flow rate requirements.

Airflow rate

Airflow rates of hydrophobic membranes are consultable by aspects like differential pressure, porosity, pore size, and effective filtration area (EFA), which eventually should guide the design of a device to maximize the filter's capability.

Thermal stability

The capacity of the filter media to preserve integrity and functionality at high temperatures is known as thermal stability. When it comes to filtering sterilization, such as autoclaving, thermal stability is crucial due to a lack of heat stability.

Compatibility of Chemicals

Chemical compatibility is described as the media's capacity to resist chemicals. The filter's function is not harmed, and the filter material does not shed particles or fibers or add extractable. It's vital to remember that compatibility is limited to a single chemical or chemical combination at a specified temperature. You must first check the Membrane Filter compatibility with the fluid before choosing it.

These are a few of the considerations that can aid you in determining the final selection of the best Air and Gas Filtration Membrane.