MULTI-STAGE SCREENING APPARATUS AND SCREEN BASKET FOR SCREENING PULP SUSPENSIONS

摘要

A screening apparatus for screening pulp suspensions comprises a screen basket (8) dividing the interior of the housing into a central chamber (10) and a single outer annular chamber. The suspension is supplied to one of the outer and central chambers, so that an accept fraction passes through the screen, while a reject fraction develops that is prevented from passing through the screen. Dilution means (28) is provided for supplying diluting liquid to dilute the reject fraction. The screen basket is divided into at least two separate tubular screen sections (40, 42). The dilution means includes at least one annular element (44) axially interconnecting the two tubular screen sections and forming a tubular dilution liquid compartment (46) extending at least substantially around the screen basket. The annular element (44) forms a plurality of dilution liquid ejection passages between the dilution liquid compartment and one of the outer central chambers. The invention further relates to a screen basket for use in an apparatus described above and a method for screening pulp suspensions.