| 摘要 |
Method and apparatus 10 permits material immersed in a body of fluid to move under the influence of gravity across inclined surfaces 14 and 24 having an angle of incline below the horizontal approximately equivalent to that of the repose angles alpha and beta of the fluid-immersed material. Such materials are moved under the influence of gravity rather than fluid forces to winnowing channels 25 comprising closed regions of finite length through which an upwelling flow of fluid at relatively high velocity passes into the fluid body in which the material is immersed. Undesired materials pass upward, borne on the upwelling flow through the fluid body while desired materials 36 move through winnowing channels 25 counter to the upwelling flow, passing along surface 251 at the repose angle beta of such material within the region of relatively high fluid velocity in accord with the material's fluid settling characteristics. Material 36 which successfully traverses winnowing channels 25 and is not thereafter borne upward on the upwelling flow settles to individual flexible walled collection means 33. Fluid isolation means 341 and 342 capable of compressing the flexible walls of the collection means 33, permit the recovery of particulate material 36 from said collection means 33 without modulating the upward flow of fluid. Preferred operation of the apparatus prescribes the processing of presized material. Empirical formulation is set forth for determining the screening size to be employed in adjacent stages of screening utilized in presizing the material.
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