Refiner plate assembly and method with evacuation of refining zone

A refiner plate assembly comprising:

• at least two substantially flat annular refiner plate mounting surfaces defined by opposing disks of a disk refiner defining a refining zone therebetween;
• a plurality of adapter subplates mounted to each refiner plate mounting surface end to end in an annular arrangement, at least one of the annular adapter plate arrangements having a segment mounting surface defining an evacuation channel extending from an intermediate location radially between inner and outer peripheries of the at least one annular adapter subplate arrangement to an opening in an outer rim of the at least one annular adapter subplate arrangement;
• a plurality of refiner segments mounted to each segment mounting surface end to end in an annular arrangement, each refiner segment having an axial refining surface with a plurality of refining bars located in the refining zone of the disk refiner;
• wherein at least one annular refiner disk arrangement is associated with the at least one annular adapter subplate arrangement and includes a filter section that is uninterrupted by the bars and includes a plurality of passages extending between the refining surface and an undersurface thereof, the plurality of passages being sized to permit steam and accept pulp fibers at the intermediate location to pass from the refining surface to the evacuation channel of the at least one annular adapter subplate arrangement.