Aluminum sulfate manufacture from aluminum dross tailings

A process for the manufacture of aluminum sulfate by the reaction of sulfuric acid and aluminum dross tailings comprising a mixture of water soluble salts, aluminum oxides and aluminum metal particles comprising:

• (a) washing said aluminum dross tailings with water to remove water soluble salts and form an aqueous slurry of aluminum oxides and aluminum metal particles containing no more than about 1 weight percent soluble salts;
• (b) heating said slurry to a temperature from 185 to about 225 degrees F. and agitating said slurry to cause sufficient particle-to-particle attrition to remove the aluminum hydroxide protective film on the aluminum metal particles to reduce the metallic aluminum content of said slurry to less than about 0.5 weight percent and thereby produce treated dross tailings,
• (c) injecting into said slurry aqueous sulfuric acid of a concentration sufficient to provide a sulfuric acid concentration of from 30 to about 60 weight percent in the resultant blend;
• (d) passing said blend through a continuous, tubular flow zone, diverting the blend therein into helical flow within said zone and repeatedly reversing the direction of rotation of said helical flow through said zone;
• (e) discharging said blend under pressure into a continuous flow reaction zone;
• and
• (f) withdrawing a crude reaction product from said reaction zone and separating unreacted solids therefrom to produce said aluminum sulfate.