Patent ID: 6387282
Filing Date: 2002-05-14
Classification: B01D

Abstract:
A process for separating solids from a liquid of a suspension in filter chambers each provided with a respective unheated flexible membrane filter element covered by a filter cloth and a rigid wall and in which a respective filter cake is formed in each chamber and is subjected to an after-compression phase, said process comprising drying the respective filter cakes by the steps of:(a) physically displacing each membrane filter element toward the respective rigid wall by introducing a pressure fluid into a compartment behind each membrane filter element to after-compress each filter cake between a respective membrane filter element and a respective rigid wall; (b) while maintaining the filter cake under after-compression between the respective membrane and wall, heating each filter cake along the respective rigid wall; (c) simultaneously subjecting the filter cakes to a vacuum to reduce a boiling point of the liquid in each of said filter cakes; and (d) controlling the temperature to which each filter cake is heated at the respective rigid wall so that a vapor layer is formed at the respective rigid wall and is propagated uniformly through the respective filter cake to drive residual liquid out of said filter cakes toward drainage surfaces of respective unheated membrane filter elements, the heating being effected over the entire area of each filter cake in contact with the respective rigid wall so that a transition zone between each vapor layer and the respective residual liquid of each filter cake transits through the filter cake homogeneously in a plane and without local vapor breakthroughs.