Abstract: There is disclosed a method for the treatment of aluminum dross oxides which contain aluminum metal, aluminum carbide, aluminum nitride and salts such as potassium and sodium chloride. The method comprises the thermal treatment of an aqueous suspension of the dross oxides with agitation in the presence of a particulate grinding medium. The method is practiced in a stirred reactor vessel which contains a bed of refractory, ceramic balls that are agitated with a slurry to provide a sufficient abrading action on the aluminum metal particles to remove the aluminum hydroxide coating and continually expose the aluminum metal for reaction with the water. This invention comprises the introduction of a purge gas into the suspension, preferably air, during its thermal treatment to reduce the formation of foam during the treatment and to assist in liberation of ammonia formed by the decomposition of the aluminum nitride.

Abstract: There is disclosed a method for the elimination of the chief impurities in aluminum dross tailings. The method can be used as a pretreatment in the manufacture of aluminum sulfate from aluminum dross tailings in a continuous flow reaction zone in which the dross tailings prior to reaction with sulfuric acid are pretreated to reduce the more objectionable contaminants contained therein to acceptable levels. The most objectionable contaminant in the dross tailings is aluminum metal which, in the invention, is oxidized with water or steam at elevated temperatures. The dross tailings, which are chiefly particles of aluminum oxide, are suspended in an aqueous slurry and the slurry is heated to a temperature from 185.degree.-225.degree. F. and maintained under liquification pressures and sufficient agitation to insure particle-to-particle attrition that removes an aluminum hydroxide coating which would otherwise inhibit the reaction.

Abstract: There is disclosed a method for the elimination of the chief impurities in aluminum dross tailings. The dross tailings, which are chiefly particles of aluminum oxide, are suspended in an aqueous slurry and the slurry is heated to a temperature from 185.degree.-225.degree. F. and maintained under liquification pressures and sufficient agitation to insure particle-to-particle attrition that removes an aluminum hydroxide coating which would otherwise inhibit the reaction. The reaction rate is accelerated by chemical and physical additives that can be optionally added to the slurry such as trace quantities of caustic, which serves as a source of hydroxyl ligands to increase the solubility of aluminum hydroxide and/or refractory particles such as ceramic spheres which increase the attrition. Other contaminants present in the dross tailings include aluminum nitride, which is decomposed to aluminum oxide and ammonia, and aluminum carbide which is decomposed to aluminum oxide and methane.

Abstract: There is disclosed a continuous process for the manufacture of aluminum sulfate by the reaction of sulfuric acid with an alumina-containing solid in an aqueous suspension. The reaction stream is passed into a continuous flow reaction zone that is maintained at a temperature controlled from 225.degree. to 260.degree. F. and under superatmospheric pressure, preferably, autogenic pressure. The reactants are passed through the reaction zone with a residence time of from 5 to about 45 minutes, sufficient to achieve from 78% to 100% completion of the reaction. An intimate admixture of the reactants is achieved by blending the reactants in a mixing zone wherein the combined streams are diverted into helical flow with repeated reversal in the direction of rotation of the helical flow during passage through the mixing zone.