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Extraction of tin from Egyptian Cassiterite Concentrate (Challenge/difficu…
Extraction of tin from Egyptian Cassiterite Concentrate
Objective
Tin is extracted by reduction of Cassiterite concentrate in the presence of sodium carbonate and sodium nitrate molten salt system at various conditions
Challenge/difficulty
Separation of tin from iron requires high temperature
High tendency to form FeSn and FeSn2
Affected by acidity of slags
Requires long reduction time due to sluggish reaction rate between solid tin oxide and carbon
Requires presence of silicate fluxes to work at high temperature
Tin oxides tend to combine with silica and goes into slag
Parameters investigated in this experiment
Carbon stoichiometry
SnO2 (s) + 2C (s) Sn (l) + 2CO (g)
Optimum molar ratio of carbon = 0.75X (91% yield)
0.75X molar ratio
produces lesser sodium salts
free from sodium stannate and lesser SnO
low carbon content increases the fluidity and hence increases the yield as well
Effect of sodium nitrate
Acts as oxidizing agent
Optimum percent by weight of concentrate = 2% with 20 wt% sodium carbonate(95% yield)
Sodium nitrate decomposes and releases oxygen. The oxygen activates the combustion of coal and promoting Boudouard reaction which increases the reduction potential to yield more tin metal.
Effect of sodium carbonate
Optimum percent by weight of concentrate = 35% (almost complete reduction)
Has the same effect as other fluxes such as silicon dioxide and calcium oxide
35% sodium carbonate by weight of concentrate
Increases fluidity
Helps separation of tin metal from slag
increases escaping of carbon dioxide
Increases reduction of tin salts by carbon monoxide
Effect of smelting temperature
Optimum smelting temperature = 1000°C (97% yield)
Lower temperature is not enough to reduce tin oxides completely
Effect of smelting time
120 mins smelting period produces mainly sodium aluminium silicates phase with sodium silicates, ferrate and titanates and traces of SnO and Sn3O4