Screen, vortex apparatus for cleaning recycled pulp and related process

An apparatus for removing ink and other contaminants from a pulp slurry of recycled paper pulp in liquid suspension, comprising:

• an upright cylindrical vessel having an upright cylindrical screen member mounted therein, said screen member being open at its top and bottom ends and comprising a cylindrical screen wall with perforations of a fine size formed through its surface, said cylindrical screen member having a given diameter defining an inner volume on a radially inward side of the screen wall and being centered on a vertical axis in the vessel;
• an open-typed rotor which does not significantly block the open bottom end of said screen member and which includes a plurality of individual blades mounted for rotation about the vertical axis in close proximity to and on a radially inward side of the screen wall of said screen member;
• an inlet provided at a bottom portion of the vessel for feeding in a pulp slurry under pressure into the bottom end and the inner volume of said screen member in said vessel, and air addition means for adding pressurized air as air bubbles into the pulp slurry fed into the vessel;
• drive means for rotating said blades to impel the pulp slurry fed into the inner volume through the screen wall and also keep the perforations in the screen wall clear while creating a rising vortex of liquid and air bubbles from the added air carrying ink and other contaminants adhered thereto moving from the bottom end of the screen member upwardly through the inner volume to the top end of the screen member;
• an accepts outlet provided at a central portion of the vessel for drawing off pulp in suspension that has been passed through the screen wall of said screen member;
• and
• a rejects outlet provided at a top portion of the vessel for drawing off a rejects stream from the vortex of liquid and air bubbles carrying ink and other contaminants moving upwardly through the inner volume to the top end of said screen member.