Modified pyrohydrolysis process for spent aluminum reduction cell linings

Abstract From the Canadian patent

Fluoridic spent and waste materials such as are, generated in electrolytic aluminum reduction systems are, pyrohydrolyzed in a fluidized bed reactor. For fluidization of these materials, as well as for the combustion of carbon present in the materials, an 02-containing gas Stream containing at least about 90% by volume 02 is, employed. This results in the generation of an HF-containing offgas of significantly increased HF level which can, be employed for the manufacture of an AlF3 product of at least about 85% by weight AlF3 content from hydrated alumina. The offgas having the increased HF content can also be employed for the production of highly concentrated HF acid with significantly …