Abstract: A double disc refiner apparatus (10) and associated method, in which two counter-rotating refiner discs (26,28) which define a refining zone (58) therebetween, are counter-rotated at different steady-state speeds, such as 1800 rpm and 1200 rpm. For energy-efficiency, the feed end disc (26) is rotated at a faster speed than the control end disc (28), but in some instances, desired refiner output quality can be achieved by rotating the control end disc faster than the feed end disc.

Abstract: An elongated, imperforate housing (2) has a slurry inlet port (5) at one end and a pulp discharge port (6) at the other end. A pressing section (2b) within the housing is in direct fluid communication with the inlet port, and extracts liquid from the slurry by passing the slurry through a first compression restriction (108) to produce a pressed pulp. An annular washing section (2c) within the housing is positioned immediately downstream of, and in direct fluid communication with, the first compression restriction. The washing section has radially inner (109) and outer (14) cylindrical walls defining an annular washing chamber (110) for decompressing, diluting, and washing the pressed pulp. The washing is accomplished by injecting a washing liquid into the washing chamber through the inner wall, and simultaneously through the outer wall while the mixture is agitated. A repressing section (2d) within the housing is in direct fluid communication with the washing section, for receiving the conveyed mixture.