Pyrohydrolysis process for spent aluminum reduction cell linings

Abstract From the Canadian patent

An improved process is provided for the recovery of HF in increased yield from spent aluminum reduction cell linings. The spent linings are pyrohydrolyzed in a fluidized bed reactor and the generated Na-containing vapors and gases are then contacted with a relatively finely divided source of Al2O3. Contacting is preferably accomplished in the close vicinity of the fluidized bed to obtain extended reaction between the Al2O3 source and the vapors. This extended reaction allows conversion of the Na-containing compounds, such as NaF and Na2O to HF and an Na2OxAl2O3 compound.