Control of the evaporation in a plasma furnace for ferrosilicon dust treatment

The treatment of oxidized ferrosilicon dusts containing zinc and lead was studied in a plasma transferred are reactor. Particles to be treated were injected either in the plasma are (in-flight treatment) or directly into the crucible (bath treatment). An ICP (Inductively Coupled Plasma) analysis system was adapted to follow on-line simultaneously and continuously the metallic element concentrations. Evaporated fraction were then determined. Comparisons of fractions according to are working parameters were performed; this allowed the control of the evaporation process during plasma operations. The in-flight treatment has led to a selective evaporation but has shown the need of a second step, since the dust treatment is incomplete when its method is used. The in-bath treatment has led to a selective and complete evaporation of lead and zinc. The value of additives such as a reductant and a slag former was also highlighted by ICP analysis.