Method and apparatus for clarifying a slurry
OwnerBror Nyman, Matti Nuoralainventors
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Abstract
The invention relates to a method of clarifying and/or thickening a solution containing solids i.e. a slurry, and the apparatus for accomplishing this. Using the method and apparatus of the present invention, the flocculant to be fed into the clarification and thickening equipment is mixed evenly and with a small shear force into the slurry in the feedwell of the apparatus. The feedwell is equipped with a mixing device. The slurry is taken onwards from the feedwell evenly into the clarification tank inside the underflow layer, which enables the separation of a clear overflow solution.
Claims16
A method to clarify and/or thicken a solution containing solids, whereby the slurry is first fed into a feedwell situated in the centre of the upper section of the settling space for clarification, where a flocculant is mixed into the slurry in the said feedwell and from whence the slurry is fed to the settling space and the settled solids or underflow is removed via a discharge port in the centre of the settling space and the clarified solution is removed as an overflow, characterised in that the flocculant and slurry are fed into the feedwell as a gentle flow and are mixed into each other using the feedwell's own mixing element, after which the mixed slurry is guided from the feedwell into a guiding cone, which is located below the feedwell and extends into the upper part of an underflow layer, and from inside the guiding cone, via openings in the lower edge of the guiding cone, into the settling space in upper part of an underflow layer as a downward directed flow.
An apparatus for the clarification and/or thickening of a solution containing solids, where the apparatus comprises a clarification and/or settling tank (1), which is equipped with a feedwell (2) for the slurry to be settled, a discharge port (9) for the settled solids or underflow in the centre of the settling tank, a discharge launder (16) for a clarified solution or overflow, and a rake system (10) rotating on its shaft (11) in order to move the underflow from the edges towards the centre of the tank, characterised in that the feedwell (2) is equipped with a mixing element (3) rotating on its shaft (4) and being a helix mixer, formed of two tubes (23) attached to a shaft (4) by means of support elements (24), which make ⅓-2 revolutions around the shaft, and a guiding cone (5) for the slurry fixed to the lower section of the feedwell being comprised of at least one conical surface (31) which is open inside and equipped with slurry guide ports (32).
Dependencies are inferred from the claim text.