A ROTATING FILTER AND A METHOD FOR FILTRATION OF A FLOWING SUBSTANCE

摘要

A filter and a method for filtration is based upon a moving filter surface (10) being caused to move through a first filtration region (FF) for separation of a pre-filtrate and a second filtration region (KF) for separation of a clear filtrate. A vacuum is applied on the filtrate side in the clear filtrate filtration region (KF) for the purpose of promoting filtrate passage. According to the invention two filtration zones (FF1 and FF2) with mutually different pressure conditions are established in the pre-filtrate region (FF). In the first filtration zone (FF1) atmospheric pressure or a relatively weak vacuum is present on the filtrate side. In the second filtration zone (FF2), a vacuum involving a pressure which is lower than the pressure in the first filtration zone (FF1) is present on the filtrate side. The pressure change between the filtration zones (FF1 and FF2) is performed in the pre-filtrate region, i.e. before the filter surface has reached the clear filtrate region (KF).