TREATMENT OF SOLID MATERIAL

摘要

2118943 9402263 PCTABS00030 A process for treatment of a solid material containing fluoride and sodium, such as spent potlining from aluminium reduction cells, comprising the following steps: 1) contacting the solid material (10) with recycled caustic liquor (14) and source of calcium (12) in a digestor (1); 2) passing the mixture to a separating device (2) to separate into liquid (18) and solid fraction (16); 3) recycling part of the liquid fraction (20, 14) containing caustic concentration of 75-200 g/l, calculated as Na2 CO3 to step (1); and 4) recovering concentrated caustic liquor (22) of concentration 180-300 g/l from liquid fraction (18). The product of the process is a solid residue having low levels of leachable fluoride and a concentrated caustic liquor.