Extraction of Tin Metal from the Egyptian Cassiterite Concentrate…
Extraction of Tin Metal from the Egyptian Cassiterite Concentrate
SnOR2R (s) + C (s) Sn (l) + COR2R (g) ……… (7)
Main reduction reactions:
3SnO2 (s) + 2CO (g) Sn3O4 (s) + 2CO2 (g) …… (2)
Sn3O4 (s) + CO (g) 3SnO (s) + CO2 (g) …… (3)
SnO2 (s) + CO (g) SnO (s) + C02 (g) ……… (4)
SnO (s) + CO (g) Sn (l) + C02 (g) ……… (5)
C (s) + COR2R (g) 2C0 (g) …… (6)
Initiation reaction: 3SnO2 (s) + 2C (s) Sn3O4 (s) + 2CO (g) …… (1)
The addition of sodium nitrate in minute amount enhanced the cassiterite concentrate.
The reduction of cassiterite is chemically controlled solid state reaction
The addition of sodium carbonate enhanced the smelting process of cassiterite concentrate.
The presence of some relics of metallic tin in the produced slags. The produced slags consist mainly of sodium aluminum silicate phases with different forms of sodium titanates, ferrates, aluminates and silicates
Presence of relics of SnO2 and lower valence tin oxides SnO and Sn3O4 in the produced slags.
The presence of sodium stannate phases in the produced slags is related to low yield of metallic tin
Factors Effecting the Smelting of Cassiterite Concentrate
Sodium Carbonate Ratio
Sodium Nitrate Ratio
Each run of the smelting process was carried out on batches containing 50 gm. of the concentrate in addition to charcoal as reductant, sodium carbonate and sodium nitrate as fluxing agents. The reactants were weighed then mixed thoroughly in fireclay scorifiers and finally transferred to a 30 cm3 volume fireclay crucible. A Muffle Furnace was preheated to the required temperature then the crucible was inserted into the furnace. After completing the reduction reaction for each run, the crucible was removed and tin metal was poured into steel mould and the slag was collected. The extracted tin metal and recovered slag were then weighed and analyzed.
Purification of Crude Tin Metal
The crude tin metal was refined with boiling process followed by liquation. In the boiling process, the tin was melted in the crucible then agitated. Most of the remaining impurities are floated on the surface to form scum, which were then removed and tin metal was poured into the steel mould. Based on the difference in melting points and the difference in specific gravity of tin alloy components, the liquation refining was carried out. The produced metal from boiling step was put on perforated funnel which was put on a crucible and then placed on the furnace . The melted tin runs down and was collected in the crucible, while the other materials remain above as solids. The high purity tin metal was then poured into the steel mould.
The slag was analyzed chemically using (XRF). Mineralogical analysis was conducted by (XRD) and Scanning Electron Microscopy (SEM - EDX) to examine the resulting phases.