Abstract: Procedure for separating finely divided matter from a suspension by filtration in a periodically operated pressure filter including a filter tank into which the suspension to be filtered is supplied along with lime sludge (or CaCO.sub.3) as a filtering auxiliary substance. The lime sludge forms a filtering layer on the surface of filtering elements and the suspension to be filtered passes through this layer for separating sediment. The pressure filter contains a plurality of filtering elements extending downwardly from the roof of the filter tank so that the filtrate flows through the elements to a superposed filtrate collecting tank. The lime sludge collects on the outer surface of the filtering elements and is periodically detached by a countercurrent washing operation. Green liquor, from which the soda sediment is to be separated, is used as the suspension to be filtered.

Abstract: An intermittently operating pressurized filter for concentrating a solid matter suspension, comprising a filtering tank with an inlet conduit provided with a feed pump for introducing under pressure the suspension to be filtered, and a draining conduit provided with valve for removal of the concentrated sludge, and a plurality of filtering elements suspended from the roof, through which the filtrate flows and of which the interior communicates with a filtrate collecting tank located above and which thereby collect on their external surface sludge, which has been arranged to be periodically removed by voiding the pressure within the filtering tank by opening for the suspension therein an exit flow path through a draining conduit. The filtrate in the collecting tank will pass in countercurrent fashion through the filtering elements.