| 摘要 |
1,216,088. Particle suspension fractionation; centrifugal separators. KARLSTADS MEKANISKA WERKSTAD A.B. 29 Nov., 1967 [1 Dec., 1966], ,No. 54263/67. Headings B1D and B2P. A particle suspension (e.g. wood plup) is given a cylindrical or conical Couette flow (i.e. the type of flow generated in a fluid contained between a pair of coaxial walls when one is rotated relative to the other); suspension rich in undesirable particles is removed from the outer zone of the Couette flow; and suspension rich in desirable particles is screened centripetally from the inner zone. The apparatus claimed comprises a cylindrical or conical housing 1; a screen drum 3 comprising one or more screens 17; an inlet 25 for suspension, a rejects suspension outlet 37; an accepts suspension outlet 45; the screen drum 3 'being rotatably mounted for the induction of a Couette flow. As described, suspension flows in at 25; through a bar screen or perforated plate 33; a rotary flow is induced by vanes 23 supported by a rotating shaft 15; and into the annular space 5. Pairwise counter-rotating Taylor's vortices are formed (these may be imagined as helical flow paths about axes which are themselves curved to form circumferences about shaft 15) which tend to keep those particles possessing lower sedimentation velocities in suspension. The centrifugal forces induced by the Couette flow tends to project the heavier (impunity) particles outwards, and this effect is felt more strongly the nearer to screen 17 the particles happen to be located, owing to the greater flow velocity there. Thus the heavier particles leave at 39, whereas the desirable particles pass through screen 17, which is kept clean by fixed back-pulse-inducing vanes 47, see also Fig. 2. A vent arrangement may be provided 'to allow released air to escape. In a second embodiment (Fig. 3, not shown) the screening surface is built up from screen plates (49) so as to present a horizontally ribbed {instead of smooth frusto-conical) screening surface (55); and there are dilution water apertures (61) in the housing wall 1. |
