The effect of admixtures on the reduction of cassiterite by graphite
The kinetics of the isothermal reduction of cassiterite by graphite with different admixtures present were studied by thermogravimetry. The conversion of cassiterite was defined as the ratio of the mass of oxygen removed from a sample to the mass of removable oxygen in a sample. Gas evolving from the reduction reaction was analysed in order to determine the pco2 /Pco ratio. This value was determined by the SnO2/Sn equilibrium so that the Boudouard reaction was the slow reaction controlling the overall rate. While MgO increased the activation energy for the reduction of cassiterite, K2CO3, SiO2, Al2O3, CaO and tin metal all catalysed this reduction and decreased the activation energy. Tin metal, CaO and K2CO3 also tended to increase the maximum conversion attainable. Whereas CaO reacted to form 2CaO·SnO2, the admixtures K2CO3, SiO2, Al2O3 and MgO revealed no reaction with the cassiterite or any other species present. © 1988.