Solids liquid separating centrifuge with solids classification

Claim 1

In a solids-liquid separating centrifuge of the type having a bowl with a reduced diameter end outlet for solids, a helically bladed conveyor within the bowl extending substantially from end to end of the bowl and arranged to move solids settling in said bowl toward said end outlet, means for rotating said bowl and conveyor about a common axis to convey a first portion of the solids settling in said bowl to said end outlet, and feed means for discharging slurry into said bowl at a feed point spaced from said end outlet, the improvement comprising: classifying means for segregating and separately discharging from the bowl a second portion of the slurry solids having mainly characteristics different from the solids principally contained in said first portion such that they are relatively slower in settling and more difficult for said conveyor to convey; said classifying means including at least one nozzle outlet through the peripheral wall of the bowl having an outlet passage with its inlet exposed to the path of movement of solids by the conveyor, intermediate the ends of the conveyor; said conveyor having a unidirectional pitch directed toward said bowl end outlet at opposite sides of said nozzle inlet, so that solids settling in said bowl at the side of said nozzle outlet remote from said bowl end outlet are conveyed thereby to said nozzle inlet, solids of said first portion are conveyed thereby across said nozzle inlet and on toward said bowl end outlet, and slurry containing solids of said second solids portion is ejected through said nozzle passage by centrifugal force; and means for collecting the outputs from said end outlet and said classifying means.