Patent ID: 6365116
Filing Date: 2002-04-02
Classification: B01F,C01F

Abstract:
A method for fluidifying flocculated aqueous suspensions of red mud in the production of alumina from bauxite in a Bayer process wherein a raking mechanism, having a rake arm including a rake blade at one end of the rake arm, is used to remove flocculated red mud, the method comprising the steps of:dissolving bauxite using sodium hydroxide to form red mud; decanting and washing the red mud, wherein one or more waters derived from the washing step are recycled to a location upstream of the washing step; separating the red mud from alumina in successive thickener vats; adding a flocculant comprising a polyacrylamide having a molecular weight greater than ten million into a suspension of red mud in one of the successive vats; pumping a dispersing agent into the red mud, simultaneously with the addition of the flocculant to the suspension in the thickener vat; wherein the dispersing agent is selected from a group consisting of lignosulfonate, a polyacrylate, a copolymer of (meth)acrylic acid and acrylamide, (meth)acrylic acid, 2-acrylamide-2-methylpropane sulfonic acid, taurine modified polymers, napthalein sulfonates, napthalein sulphonated derivatives, and hydroxymethyl diphosphonic acid polymers, and the rake arm comprises a hollow conduit connected to a reservoir containing the dispersing agent, the rake arm further comprises at least one opening for delivering dispersing agent to the vicinity of the rake blade, and eliminating the red mud thus treated.