Alcan International Limited

Donald L Puxley

Guy Peloquin

Andrew N Carruthers

Renald Dufour

Ronald D Paradis

Peter F Bagatto

Fitzgerald Stewart

Fusanosuke Iida

Method and apparatus for separating components of slurries by gravity settling thereby forming a thickened slurry and a clarified liquid. The apparatus comprises a vessel for decanting a volume of slurry, the vessel having a top and an interior formed by a side wall and a bottom wall for holding the slurry, a slurry inlet means, an outlet for the clarified liquid near the top of the vessel, and a slurry withdrawal apparatus for removal of the thickened slurry from the vessel at or near the bottom wall thereof. The slurry withdrawal apparatus physically engages a portion of the slurry within the vessel interior and transports it through a vessel outlet. The apparatus may include an elongated, rotatable, open spiral-shaped element extending a distance into the vessel from outside near the bottom wall of the vessel, the open spiral-shaped element being in direct and open communication with the interior of the vessel over at least a significant portion of the distance, and a rotational drive mechanism for rotating the open spiral-shaped element, at least intermittently.

Apparatus for production, withdrawal and transfer of highly viscous slurry

A method of and apparatus for removing a slurry having shear-thinning visco-plastic rheological properties from a reservoir containing a body of the slurry of such high viscosity that removal is impractical by conventional means, such as gravity flow or suction. The method comprises creating a flow of shear-thinned slurry in a submerged region of the body of slurry to entrain adjacent slurry of high viscosity, and then transferring some of the reduced viscosity slurry from the reservoir. The flow of shear-thinned slurry may be produced by withdrawing slurry from an outlet point in a region of the body of slurry to create a flow of withdrawn slurry, subjecting the flow of withdrawn slurry to shear conditions to form a withdrawn slurry of reduced apparent viscosity, and introducing the withdrawn slurry of reduced apparent viscosity into the region of the body at an inlet point therein spaced from the outlet point, the inlet and outlet points in the region being positioned relative to each other to create a flow or stream of slurry of reduced apparent viscosity through the region carrying therewith slurry of higher viscosity, and removing some of the slurry withdrawn from the region permanently from the reservoir. The apparatus provides conduits and a shear-generating device communicating with the reservoir and an outlet conduit for slurry permanently withdrawn from the reservoir.

Transfer of shear-thinning slurries

An apparatus for separating solids suspended in incoming pressurized liquid slurry is disclosed. The apparatus comprises a vessel having an elongated cylindrical vessel wall, a closed upper end and a bottom section for accumulation of solids. The vessel includes a stirrer mounted for rotation along an inside surface of the bottom section and a discharge spool mounted beneath the bottom section including at least one opening. An underflow pump is provided for discharging separated solids without loss of pressure in the apparatus. The apparatus further includes means for detecting solids level in the apparatus, which preferably operates without disturbing settling of the solids therein. Also, the apparatus includes a feedwell for receiving an incoming pressurized slurry stream, the feedwell having an opening a predetermined distance above a level in the apparatus defined by settled solids.

Pressure decanter

A method of and apparatus for the thickening of mud-like slurries produced during the course of industrial processes, e.g. the thickening of red muds produced during operation of the Bayer process for the production of alumina. The invention involves the step of feeding the slurry, a fluocculating agent and washing liquor to a deep thickening vessel having an underflow outlet for the thickened slurry and an overflow outlet for clarified washing liquor. The solids content of the slurry leaving the underflow outlet is increased and kept constant by the use of a stirrer having a number of generally vertical rod-like members rotated in the vessel above the underflow outlet. The stirrer enhances dewatering of the slurry and prevents undue build up of thick inactive mud which may block the outlet or cause fluctuations in the solids content of the thickened slurry.

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Jonquiere, Canada

Donald L Puxley