Apparatus for screening to remove knots from a fluid borne slurry of fibres and knots.

摘要

A screening apparatus (20) removes a fluid borne pulp fibre slurry from knots which have been concentrated from a pulp processing stream. A rotating radially symmetrical screen (30) provides centrifugal screening to accept a pulp fibre slurry while an integrally connected spiral flight conveyor (17) transports knots from the inner surface of the screen to a knot discharge chamber (34) located axially above the screening chamber (62). Above the screening chamber but below the liquid level (65) in the housing (14), a fibre free wash liquid is provided through a tangentially orientated nozzle (32) in the direction of rotation of the spiral flight conveyor to release fibres from the knot surfaces thereby enabling them to pass through the screen. The screening apparatus also provides for removal of heavy tramp materials, for maintaining liquid level control, for minimizing air entrainment and foam formation, and for preventing clogging of the screen apertures and knot discharge outlet. <IMAGE>