Volatilisation of Lead by Using Chlorination Agent Magnesium Chloride

Zinc- and lead-containing waste materials such as steel mill electric arc furnace dust are mainly processed by the Waelz process (volatilisation under reducing conditions). Especially, the addition of carbon as reducing agent to the initial mixture contributes to the desired reaction kinetics and progress. However, the removal of the element lead is not completely. It remains partly as water-soluble compounds in the Waelz slag in the order of magnitude of 3 mass % which prevents the use in road construction. Starting from the idea lead can be volatilised by using an additional chlorinating agent like magnesium chloride first principle investigations are made. Therefore the pure model substances PbO, MgCl2 and C are used. The formation and volatilisation of PbCl2 is assumed, because of its high vapor pressure. Favorable thermodynamic conditions exist in particular for MgCl2 as chlorinating agent. It should therefore be clarified how far PbO reacts with MgCl2 - also in the presence of C - to PbCl2 in a temperature range of 800 to 1000 °C. First experiments show promising results, not only for the pure substances but also for electric arc furnace dust.