PROCESS FOR CONVERTING DROSS RESIDUES TO USEFUL PRODUCTS

摘要

A process for converting dross residues having an aluminum nitride content of at least 5 wt % and a metallic aluminum content of no more than 10 wt % ( particularly plasma dross residues) to useful products. The process comprises treating the dross residues with a solution having a pH of 7 or more, the reaction at alkaline pH values being AlN + 4H2O -> Al(OH)3 + NH4<+> + OH<-> followed by: Al(OH)3 + OH<-> -> Al2O<-> + 2H2O and NH4<+> + OH<-> -> NH3 + H2O. The initial treatment of the dross residues may be under mild conditions to generate ammonia from the nitride. The ammonia can be collected as a useful product or converted to other useful products such as ammonium salts. Under harsher conditions, e.g. elevated temperature and pressure with caustic alkalis, a substantial portion of the dross residue dissolves to form an alkali metal aluminate solution which is itself a useful product (e.g. it can be used in the Bayer process) or can be converted into other useful products such as aluminum trihydrate. A portion of the dross residue normally remains undissolved and this can also be a useful product, e.g. a refractory precursor, or may be disposed of by dumping since it is non-polluting.