Filtration and classification of the filter
In order to meet the different requirements of different separation objects, filtering methods and equipment are varied. To master the filtering technique, the filtering must be properly classified.
(1) According to the mechanism of the process can be divided into filter cake filter and deep filter.
Filter cake filtration. Filter cake application of fabric, porous solid or porous membrane as a filter medium, the pores of these media is generally smaller than the particles, the fluid can be filtered through the media pores, the size of particles, can not enter the pores and filter media retention filter cake. Therefore, the retention of particles depends mainly on the screening action.
In fact, the pore size of filter media used in filter cake filtration is not necessarily smaller than the diameter of the particles. At the beginning of filtration, some particles can enter the pores of the medium, and some particles may make the filtrate turbid through the medium. With the extension of the filter, many particles together into the orifice, the orifice orifice on the formation of bridging phenomenon, when the concentration of solid particles is high, the bridge is very easy to generate. At this time the actual pore size of the media is reduced, small particles can not be trapped by the formation of filter cake. The filter cake in the subsequent filter to play a real role in the filter media, the cake as a small pore, very small particles were also retained, so that the filtrate becomes clear, then the filter can be truly effective,
Filter cake is carried out on the surface of the medium, also known as surface filtration. Cake filtration is commonly used to treat suspensions with solid volume concentrations greater than 1% due to clogging of the media in the filtration of dilute suspensions. For dilute suspensions, by means of artificially increasing the feed concentration, a filter aid can be added as a slurry to form filter cake as soon as possible, and since the filter aid has many small holes, the permeation of the filter cake is enhanced , So that generally difficult to filter slurry can filter cake.
