| 摘要 |
A fully integrated process is provided for the recovery of valuable components from waste materials in electrolytic aluminium reduction systems. The waste materials, such as spent pot linings, channel and trench cleanings, floor sweepings and spent alumina from offgas purifying dry scrubbers, are combined, then pyrohydrolyzed at elevated temperature. Fluoridic values, such as NaF and HF can be recovered from the offgas generated by pyrohydrolysis, while alumina and Na20 values, or if desired, sodium aluminate, is reclaimed from the solid residue of pyrohydrolysis. The fluoridic values from the pyrohydrolysis offgas can be used for the manufacture of both electrolytes for aluminium reduction cells and also for the production of anhydrous HF. The alumina from the pyrohydrolysis residue can be reclaimed by a Bayer processtype leach with a caustic solution and the recovered high purity alumina utilized, for example, as reduction cell feed and/or for scrubbing reduction cell offgases. If the solid residue of pyrohydrolysis contains significant amounts of sodium aluminate, this material can either be directly used for dry scrubbing cell offgases, or if desired, utilized for production of high purity alumina. |
