Patent ID: 6409929
Filing Date: 2002-06-25
Classification: B01D

Abstract:
A method for the removal of moisture from a filter cake formed on a filtering surface of a filtering apparatus comprising:a rotatable filter including a filtering surface on which said filter cake is formed; a suspension trough in which said filter is rotatably positioned; a pressure tight housing in which said suspension trough and said filter are completely enclosed in a pressure tight manner, said pressure tight housing defining a first pressure chamber filled with a pressurized first gas at a pressure above atmospheric, said first gas being used for generating a differential pressure for forming the filter cake on said filter; a hood positioned within said pressure tight housing, said hood covering at least a section of said filtering surface, thereby defining a second pressure chamber, said second pressure chamber containing gaseous treatment fluid which is different from the first gas, said gaseous treatment fluid being heated vapour for treating said filter cake, the method comprising: presenting the filter cake in a liquid saturated state saturated with a mother liquid; exposing and condensing the gaseous treatment fluid to form a liquid phase of the treatment fluid while the filter cake is in a liquid saturated state saturated with the mother liquid; wherein a pressure and temperature of the treatment fluid is set such that; a thermodynamic state-point of the gaseous treatment fluid is near a condensation point of the gaseous treatment fluid; the treatment fluid initially penetrates into a top layer of the filter cake furthest away from the filtering surface, cools and condenses thereby forming a condensation front in an area of the filter cake; the filter cake is progressively heated up by the treatment fluid to the temperature of the gaseous treatment fluid from the top layer to the filtering surface; and the condensation front is displaced towards the filtering surface; and by displacing the condensation front the mother liquid is replaced by the treatment fluid.