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Abstract

A lime slaking system for hydration of lime and removal of unwanted grit, particularly for formation of reactive slaked lime to be used in SO.sub.2 scrubbing of effluent gases, comprising a series of slaking vessels (10, 12) for reacting CaO and water while agitating the reactants, a dilution mix tank (14) receiving a viscous slaked lime slurry from the vessels, diluent for the dilution tank comprising an upstream classifier overflow stream (16), a cyclone (19) receiving pumped diluted slurry from tank (14), the overflow (21) of the cyclone providing usable slaked lime product and the underflow (22) exiting to the upstream classifier (24) where grit materials are separated and removed. Dilution for effective classification is provided by spent scrubbing process water containing appreciable sulfate ions. Detention time is such in the classifier (24) along with presence of a prescribed amount of slaked lime exiting the cyclone underflow (22), to allow precipitation of the sulfate ion as gypsum in the classifier (24) to prevent scaling in the gas scrubbing equipment. Optionally an attrition machine (30 ) may be incorporated along with a subsequent classifier (32) to recover any occluded slaked lime particles reporting with the grit discharge (27) from classifier (24).

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First Claim