To separate solids from liquids, nonwoven or woven fabrics out of animal or vegetable fibers are used, and synthetic fibers are now in use since several decades. In cross-flow filtration the filtrate is recuperated transversely to flow direction through a porous wall layer. In classic filtration, a filter cake is built up on filter surface and this cake reduce the flow of filtrate which will depend of the cake permeability. Often it needs such a cake structure build-up in order to obtain a clear filtrate. The filtration of slimy products such as proteins, polymeric carbohydrates or microorganisms was with the classical methods of filtration is quite costly or even impossible.
The characteristic feature of the cross-flow filtration is the high flow velocity over the filter surface, which avoid the build-up of a cake.
Cross flow filtration may be sufficient to achieve a filtration efficiency for separation of fine inorganic particles of a few micrometers in a low viscosity solvent.