Abstract: A thickener for liquids or pulps includes a tank in which flocculation takes place. A feedwell for feed liquid is disposed within the tank and has a restricted bottom opening in fluid communication with the tank. The bottom opening has an effective cross-sectional flow area substantially less than the mean cross-sectional area of the feedwell to restrict the flow of liquid between the tank and the feedwell through the bottom opening and thereby promote homogeneous mixing of the feed liquid within the feedwell. A conduit supplies feed liquid to the feedwell. An aperture is formed in the feedwell or the conduit above the bottom opening and below the upper marginal edge of the feedwell to permit the recirculation of dilute liquid directly from the tank through the aperture and into the feed liquid when the surface level in the tank is higher than the surface level in the feedwell to provide for autogenous dilution of the feed liquid.

Abstract: A thickener for liquids or pulps comprising a tank in which flocculation takes place and dilute liquid is displaced toward the top of the tank, a feedwell having a bottom opening in fluid communication with said tank, conduit means to supply feed liquid to said feedwell, and apertures in said feedwell or said conduit disposed above said bottom opening and positioned to permit the flow of said dilute liquid directly from the tank into the feed liquid for dilution thereof.The thickener preferably comprises a weir plate assembly connected with a side wall of the feedwell adjacent a side opening therein. The weir plate is preferably moveable by means of a float assembly between an open position permitting said dilute liquid to flow from the tank to the feedwell, and a closed position substantially closing the side opening.