The pressure behind the slurry (typically 100 psi, but up to 900 psi [7 to 60 bar]) is provided by a feed pump—sometimes a positive displacement or centrifugal pump. With a gravity drain on the filtrate side of the press, a pressure differential between the feed pressure and the gravity discharge is created across the media and the filter cake solids as they build in thickness.
It is the existence of this pressure differential, not just the feed pump pressure, that causes the filtering action to occur. Solids within the slurry will flow to the area of cake development with the lowest pressure differential, resulting in a filter cake that builds uniformly over the drain-field on either side of the chamber walls.
This fill cycle continues until the filter cakes forming on the chamber walls bridge at the center, completely filling the press with solids. It is at this point that the filtration process is complete.
Once this is achieved, the hydraulic closure of the press is retracted, the individual filter elements are separated and the filter cakes are discharged, usually by gravity, to an appropriate receptacle. Click to go back to FAQ page