Abstract: A high consistency pulp refiner of the type having a pressurized casing (12) containing opposed grinding discs (14,18) mounted for counter-rotation about a common axis (26) and between which material to be refined is introduced near the axis so as to move generally radially outwardly through an inner refining zone (40) between the discs while producing steam as a result of the refining action. The partially refined material and steam then move through a generally radially outer refining zone (50) between one of the discs (14) and a stationary grinding surface (54) situated generally radially outwardly of the other disc (18), whereupon the refined material and steam are discharged from the casing through a material outlet (62).