Method and an apparatus for treating fibre suspensions

Claim 1

An apparatus for fluidizing and screening a fibre suspension of consistency 5-15% to remove therefrom solid foreign particles, which apparatus comprises a housing, an inlet in the housing for receiving inflowing fibre suspension mixed with solid foreign particles; a first outlet in the housing for discharging part of the suspension liquid and said solid foreign particles; a stationary screen positioned in the housing to define a filtering enclosure extending between said inlet and said first outlet, the screen having an inner surface and a plurality of apertures, a rotor disposed within said filtering enclosure for rotation therein to apply to the suspension fluidizing forces breaking up interlocked fibre flocs present therein and thereby fluidizing a part of said suspension to exit therefrom through said screen; a second outlet communicating with the exterior of said screen to allow exit of fluidized suspension; said rotor having a plurality of radially extending planar blades supported by a central shaft, said blades having an outer edge, said blades extending continously towards the inner surface of the screen, from the rotor shaft, said screen having a plurality of radially extending ribs inwardly directed to a predetermined clearance with the outer edge of said radially extending blades, each of said ribs having an outer end, said blades having a height greater than the height of said ribs, the height of the blades being such that said predetermined clearance is sufficient to establish fluidizing forces acting upon the suspension, and wherein said first outlet is approximately the same size as said inlet to accommodate exit of said solid foreign particles.

Claim 2

An apparatus for fluidizing and screening a fibre suspension of consistency 5-15% to remove therefrom solid foreign particles, which apparatus comprises a housing, an inlet in the housing for receiving inflowing fibre suspension mixed with solid foreign particles; a first outlet in the housing for discharging part of the suspension liquid and said solid foreign particles; a stationary screen positioned in the housing to define a filtering enclosure extending between said inlet and said first outlet, the screen having an inner surface and a plurality of apertures, a rotor disposed within said filtering enclosure for rotation therein to apply to the suspension fluidizing forces breaking up interlocked fibre flocs present therein and thereby fluidizing a part of said suspension to exit therefrom through said screen; a second outlet communicating with the exterior of said screen to allow exit of fluidized suspension; said rotor having a plurality of radially extending planar blades supported by a central shaft, said blades having an outer edge, said blades extending continously towards the inner surface of the screen, from the rotor shaft, said screen having a plurality of radially extending ribs inwardly directed to a predetermined clearance with the outer edge of said radially extending blades, each of said ribs having an outer end, said blades having a height greater than the height of said ribs, the height of the blades being such that said predetermined clearance is sufficient to establish fluidizing forces acting upon the suspension, and wherein said first outlet is approximately the same size as said inlet to accommodate exit of said solid foreign particles.