The Mechanism of Pb
removal from brass scrap by compound separation using Ca andNaF addition was
investigated.Because
large Ca-Pb compound particles formed by Ca addition rise to the surface of the
molten brass, they can be skimmed off from the molten brass. However, fine
Ca-Pb compound particles remain in the molten brass because of low buoyancy. By
subsequent NaF addition, the reaction between Ca-Pb compound and NaF takes
place at their contact regions, resulting in the formation of solid CaF2,
liquid Pb and Na gas. Pb is mainly present at the Ca-Pb compound-CaF2 interface. CaF2 acts as a binder for aggregation of fine Ca-Pb
compound particles, resulting in the formation of light and large composite
compounds, which rise to the surface of the molten brass. A high Pb removal
rate is achieved by skimming off.
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