PROCESS AND APPARATUS FOR DECANTATION OF SUSPENSIONS

摘要

A process and apparatus are useful for decanting suspensions at temperatures at and above the atmospheric boiling point of the liquid of the suspension. The apparatus is in the form of a vertically elongated vessel of high height to diameter ratio having a cylindrical upper section (10) and a bottom section (12) and arranged to be filled to a predetermined liquid level (13) in an upper region of said cylindrical section; feed means (17) for feeding a suspension into the cylindrical section in a mid-region between the bottom of the vessel and said liquid level, said feed means including means for injecting the feed under a positive pressure sufficient to overcome the hydrostatic head of the liquid in the vessel above the feed inlet; means (20) for adding a flocculant to the suspension feed; liquid outlet means (14) in an upper region of the cylindrical section at or below said liquid level for drawing off clarified liquid; solids discharge means (30) at the bottom of said vessel; means (22, 23) for controlling a slurry-clarified liquid interface at a predetermined level in a lower region of said cylindrical portion below the feed inlet and rotatable rake means (24) in the bottom section adapted to remold the sedimented solids and continuously expose renewed surfaces. It is particularly useful for clarifying caustic liquor containing red mud residues from the Bayer process.