Patent ID: 7560008

Claim:
A method of treating comminuted cellulosic fibrous material in a liquid slurry using a screen having a screen surface with a plurality of parts, comprising: (a) causing the slurry to move downwardly past the screen; (b) withdrawing liquid from the slurry through a first part of the screen surface for a time period sufficient to avoid severe compaction; (c) relieving the compaction force on the material of the slurry at a second part of the screen surface substantially immediately below the first part so as to encourage springback of the material; and (d) repeating (b) and (c) at least once in following part of the screen surface as the slurry continues to move downwardly, wherein steps (a)-(d) are practiced at a first vertical position in a continuous treatment vessel, and then are repeated at a second vertical position in the continuous treatment vessel, vertically spaced from the first position, and wherein step (c) is practiced at a solid part of the screen surface having a step-out and a portion angling inwardly below the step-out, at both the first and second vertical positions.