in a slurry dewatering process , slurry is pumped into a porous tube at a sufficiently low velocity for laminar flow conditions to exist . the pressure is sufficiently high for liquid in the slurry to permeate outwardly through the tube wall and for solids in the slurry to be deposited in the form of an annular cake on the tube wall . the deposition of solids is controlled so that the cake thickness is substantially uniform throughout . when a predetermined thickness of cake has been deposited , the pressure inside the tube is decreased and the flow velocity is increased and the cake is dislodged from the tube wall in flake form and is conveyed downstream for collection on a screen or the like .