Leaf Filters are ideal for solid-liquid separation & work on principle of precoating & pressure.
Pre-coating is done with the help of suitable filter aid about 0.5 to 1% (Bleaching earth, supercel, hyflo, superflo etc.) mixed with the liquid to be filtered. Unfiltered liquid is pumped into the filter vessel. Initially the filter aid starts forming a precoat layer on both sides of the filter leaves, until then cloudy material comes out of the filter. Once the layer is formed, pressure starts developing, restricting the impurities. Clear liquid flows from both sides into the leaves (filter elements), flows along the tubular channel & gets discharged from bottom of the leaf. All the leaves are mounted on a common manifold. The leaves start getting choked on both the sides by impurities forming cake, which is in wet from. Once the leaves get choked completely, the pressure rises to 3 kg/cm2 & the output flow almost stops. This means the batch size is reached. The pump is stopped & steam / air pressure is applied from the top (without dropping the filter pressure) to filter the material around the leaves held up in the tank & to squeeze the cake further & reduce the liquid retention in it. The holdup unfiltered liquid in the conical portion is taken back.