The filtration of a dispersed system is a separation process, in the course of which the dispersed constituent is separated from the fluid dispersion medium by means of the filter. Compressed air ensures here that the fluid can flow through the filter. According to the structure of the porous substances, filters are subdivided into
- fibre filters
- pore filters
- granular filters.
A fibre filter consists of a relatively thin layer of fibres, the fibres being of approximately equal thickness and arranged normal to the flow of gas roughly equidistant from each other. A pore filter is, e.g., a membrane filter; a granular filter consists of spherically shaped filtration elements, or granules. An effective assessment of filtering performance can be carried out only if the characteristic values of filtration are used as criteria. The most important characteristics are:
- Separation efficiency
- Pressure loss
- Penetration co-efficient
Separation efficiency and pressure loss are functionally interdependent in accordance with E = f (delta p). For filtration efficiency it is important to select filters which combine maximum separation potential with minimum pressure loss and where these two parameters remain constant during the service life, i.e. do not change with time.
