In chloride hydrometallurgy either HC1 or Cl2 has to be regenerated in order to establish an economically viable metallurgical process. One such process is used with steel pickling where HCI is regenerated through the thermal decomposition of ferrous chloride in either a spray roaster or a fluid bed pyrohydrolyzer. The HCI regeneration process deserves to be considered as a potential metallurgical separation process, since thermodynamic calculations show that a pyrohydrolyzer can function as a ferrous-nonferrous separator. Several nonferrous metals such as zinc, lead, and cadmium can be volatilized as a chloride under ferrous chloride pyrohydrolysis conditions. If such a nonferrous metal volatilization could be achieved in the case of slurry feeding of #x201C;contaminated#x201D; iron oxides, then this would increase the Fe/H30 ratio and thus save on fuel per ton of iron, while yielding a marketable iron oxide product. Previous work on synthetic materials revealed that the separation of zinc, cadmium, and lead from iron oxide was possible in a pyrohydrolytic atmosphere, even if the zinc was present as zinc ferrite. This investigation which was carried out in a tube furnace, has been extended to treat franklinite ore. Il was found that only 65 zinc volatilization could be achieved in 6 hours due to the presence of Mn and Si oxides. Complete zinc volatilization could not be attained due to the formation of rhodonite and willemite, which are stable in the pyrohydrolytic HCl/H20 atmosphere. The effect of adding small amounts of calcium chloride to react with willemite to give zinc chloride and calcium silicates is discussed.
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