Sintered mesh Particle filtration and cleaning for industrial applications

Understanding the fundamental dynamics of particle separation as a fluid stream passes through a filter media and then the after cake removal is crucial to suitable selection of suitable media and to successful filter design and operation. From the standpoint of filtration processes, the two basic modes of filtration are dead-end and cross- flow. Additionally, the location of particle capture further complicated filter media design and selection for a specific application that are the particles basically captured within the depth of the media or on the media surface.

The types of particle filtration used in dead-end filtration are depth filtration and surface filtration. In case of depth filtration, the particles are held in the media while in surface filtration they are retained, at the surface where after a cake of particles is developed. These types should be considered to ensure suitable media design and choice for a specific industrial application.

Depth filtration in gas and liquid service is mainly used in applications where low particle levels should be separated, to secure downstream equipment, for product purification to meet health, safety and environment requirements. The particles penetrate in the media and are subsequently held within its multiple layer structure. The multiple layer structure prevents premature blocking of the media and increases capacity for particle holding and on-stream lifetime. As the particles held in the depth of the media, the filters are meant to be used once or cleaned off-line. This cleaning can be accomplished with solvents, ultrasonic vibration, pyrolysis, steam cleaning or water back flushing.

Surface filtration by sintered wire mesh in liquid applications mainly uses particle capture through straining mechanism where particles larger than the pore size of the filter media are separated at the upstream surface of the filter, their size prevents them from entering or passing through the pore openings. In gas service, particles are held on or near the filter surface through additional capture mechanisms, i.e. primarily impaction, interception and diffusion. For both liquid and gas service, after particles accumulate as a cake that increases in thickness as more particle laden fluid is forced on the filter media. The cake, with its potentially finer pore structure may aid in the separation of finer particles than can be received through its as filtration proceeds. 

As surface filters are not perfectly smooth or have perfectly uniform pore structure, depth filtration of finer particles may occur that will influence the filter life. So, selection of optimal media grade and knowledge of the particle size distribution particularly the finer particles, is important to achieve long filter service life.

Sintered mesh filters used in high particle loading applications discovered in both gas and liquid services are usually online back pulsed cleaned to increase filter life. The operative filtration mechanism becomes cake filtration as the media is particularly engineered to ensure surface filtration and the feasibility of cake particulate removal through pulse blowback cleaning. A particle cake is developed on the surface of the filter media that becomes the filtration layer and results into further pressure drop.