Process for the utilization of waste materials from electrolytic aluminum reduction systems

Claim 1

An integrated process for recovering aluminum, alkali metal and fluoridic values from spent and waste materials generated in electrolytic aluminum reduction systems and containing the same which comprises: (a) charging a feed selected from the group consisting of spent carbonaceous potlinings, channel cleanings, trench cleanings, floor sweepings, spent alumina scavenger from dry scrubbers employed for purifying aluminum reduction cell offgases, and mixtures thereof, into a furnace; (b) subjecting the charge in the furnace to a thermal treatment at a temperature within the range of about 1100° and 1350° C. in the presence of sufficient water to provide pyrohydrolysis conditions resulting in the generation of an offgas containing volatilized fluorine values in the form of alkali fluorides and HF with the simultaneous production of a residual clinker being essentially free of volatilizable fluorine values, and containing alumina and Na 2 O values; (c) removing and cooling of the offgas to obtain the alkali fluorides in solid form, which are separated from the residual offgas stream; (d) recovering HF from the residual, essentially alkali fluoride-free offgas; (e) discharging the clinker from the furnace and subjecting the clinker to alkaline digestion under Bayer process conditions resulting in an alkali aluminate solution from which alumina in high purity is recovered and in a residue containing essentially all of the undesirable impurities from the spent and waste materials.