PYROHYDROLYSIS FOR RECOVERING FLUORINE* ALUMINUM AND SODIUM FRACTION FROM USED AND WASTE MATTER GENERATED FROM ELECTROLITIC ALUMINUM REDUCTION INSTALLMENTS

摘要

A pyrohydrolysis system is provided for the recovery of valuable components from waste and spent materials generated in electrolytic aluminum reduction facilities. The pyrohydrolysis system employs a dense phase fluidized bed reaction zone for the pyrohydrolysis of coarse feed, a dilute phase fluidized reaction zone for pyrohydrolyzing fine feed, this zone being superimposed and interconnected with the dense phase zone. The offgases, after removal of the solids, are contacted in a dilute phase fluidized zone, with a source of Al2O3 to remove residual Na values and to produce Na-free HF. The solids from the first dilute zone, having a desired high Na:Al atom ratio, can be combined with the product clinker from the dense bed zone. The offgas, containing the source of Al2O3, is subjected to solids separation, the solids-free and Na-free HF is utilized, while the solids of low Na:Al mole ratio are recycled to the residual Na conversion step.