762
K. Miwa et al.
Fig. 3 Stock of tin-enriched-dross (before recovery system installed)
Sn Recovery System
To deal with the tin increase, new recovery system has been installed. Figure 4 shows
the process of tin recovery and metal tin production.
Tin Smelting (Reduction)
Tin-enriched-dross from lead purification process is fed to tin smelting section. The
main facility is electric furnace, having a 1.8 m diameter and 1.6 m height. The
outlook of the furnace is shown in Fig. 5.
Coke and dross are together inserted into the furnace and following reduction
reactions occur.
SnO 2 + 2C = Sn + 2CO
PbO + C = Pb + CO
The product is called “Sn–Pb metal”. The typical content of the metal is shown
in Table 3.
Molten Sn–Pb metal is tapped from the furnace and casted into ingots having
about 500 kg weight. The ingot is transported to the next process, leaching section.
Leaching
At the beginning of leaching section, Sn–Pb metal ingot is again melt and pulverized
into powder style having 200 µm diameter. This process is aimed at dissolving tin
effectively.