| 摘要 |
PURPOSE:To recover ZnCO3 with hardly any impurities, such as Fe and Pb, by heat-treating a kiln dust in an oxidizing atmosphere, dissolving the heat- treated kiln dust in sulfuric acid and adding Na2CO3 to the resultant solution. CONSTITUTION:Reduced iron is removed from a dust generated from iron mills by using a kiln 5 and the residual kiln dust 6 is heat-treated at >=400 deg.C temperature 7 in an oxidizing atmosphere. The heat-treated kiln dust, as necessary, is then subjected to wet magnetic separation 8, filtration 9 for removing an Fe-rich slurry or directly dissolved in sulfuric acid 10. The resultant sulfuric acid solution is subsequently filtered 11 to remove Fe and Pb left on the filter. On the other hand, Na2CO3 is then added to the obtained filtrate after removing the Fe and Pb and neutralization and crystallization 12 are carried out by exothermic reaction expressed by the formula to recover ZnCO3. The crystallized slurry is subsequently filtered 13 to dry 14 the formed cake using heavy oil, etc., and utilized as a raw material for Zn based plating (e.g. pure Zn, Zn-Fe or Zn-Ni). Na2SO4 is concentrated and separately utilized as Glauber's salt, such as fertilizer.
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