Patent ID: 7913942

Claim:
A refiner comprising a stator and a rotor, the stator and the rotor each comprising a planar portion and a conical portion outward of the planar portion, the planar portion and the conical portion each comprising refining surfaces provided with blade bars defining blade grooves therebetween, and the planar portions of the refining surfaces of each of the stator and the rotor comprising at least two serially-disposed refining zones extending radially along the planar portion, wherein at least the planar portion of the refining surface of the rotor includes blade bars disposed in radially outermost refining zone, the blade bars having a blade bar angle configured so as to provide pumping blade bars, with the blade bar angle being greater, at least on a radially outermost portion of the radially outermost refining zone of the planar portion, than the blade bar angle of the blade bars in the previous refining zone disposed radially inward from and adjacent to the radially outermost refining zone of the planar portion, and wherein the blade bar angle of the pumping blade bars of the radially outermost refining zone is between about 5 degrees and about 50 degrees with respect to a radius of the planar portion so that the blade bars in the radially outermost refining zone have an overall pumping effect on material to be refined.