30 PPI Foam means a foam ceramic filter plate product with a pore uniformity of 30 holes on any 25.4mm length. Foamed ceramics are usually made of polyurethane foam as carrier, and then poured into ceramic slurry made of fine powder of fire-resistant aggregate sintering agent and binder. Then, the slurry is extruded, and the ceramic material wrapped around the foam fiber is left. After drying, it is calcined and sintered at high temperature, and the polyurethane resin is decomposed by heat, leaving foamed ceramic products. That is, ceramic foam filter material for filtering aluminum alloy liquid is Al2O3.
30 PPI Foam
The number in front of PPI represents the pore density of the product. If the model is 30ppi, it means a foam ceramic filter plate product with a pore uniformity of 30 holes on any 25.4mm length.
The filtration mechanism of ceramic filter was screened. Like a sieve, the inclusion particles and their agglomerates which are larger than the diameter of the filter surface are prevented from passing through.
Cake filter. After screening, many inclusions larger than the filter holes are trapped at the inlet end of the filter. With the increase of the number of trapped inclusions, a “filter cake” is formed on the surface of the filter inlet. The “filter cake” makes the liquid thinner, so that the size of the filter aperture is smaller than that of the filter, and some inclusions are trapped on the “filter cake”.
Deep bed filtration. Inside the ceramic foam filter, the path of the melt flows through a winding path, and there are even transverse flow reentry phenomena in the small local area.
30 PPI Foam Filter Functions
(1) It can greatly increase the probability of the contact between the inclusion particles and the filter.
(2) Make the flow velocity and flow direction of the melt change faster, so that the small inclusions in the melt can be left behind in a certain corner after being collided and captured.