Filtration is the separation of solids from a suspension in a liquid through a porous barrier or screen which retains most of the solid particles but allowing most of the liquid through. On a laboratory scale, filtration is usually carried out with a Buchner funnel sucking the liquid through a thin barrier using a vacuum. When filtrating on an industrial scale difficulties are encountered due to the handling of much larger quantities of solids and liquids. To have a clear overview of what kind of filter is suitable for its application filters and filtration can be classified in different ways: By Driving force Gravity, Applying pressure upstream, Applying vacuum downstream. By Filtration Mechanism Although the mechanisms for separation and accumulation are not clearly understood two models are usually taken into account: Cake filtration, where solids are stopped on top of the filter medium Clarifying filtration, where solids are trapped between the …show more content…
Filtration: theory
Filtration has evolved to be more of a practical activity rather than a theoretical science, which also brings challenges. However, the filtration theory has kept many scientists and engineers busy with the effort to quantify the common engineering rate relationship: Rate=(Driving force)/Resistance
Where, for general filtration, the resistance is the sum of the filter medium and the cake. Theory is never used as the only basis for the design of a filter, however, it is valuable to interpret laboratory results and predict operation conditions. The use of filtration theory is limited due to the fact that the filtering characteristics must always be determined for the to be filtered slurry. Data from one slurry cannot be compared to that from another. This is due to the role of the nature of the solid particles and their interaction, which is a complex matter that requires a lot of