The reduction of Masuku cassiterita concentrate by charcoal and carbon monoxide
Nyirenda, Ralton Latoni
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The reduction of Masuku Cassiterite gravity concentrate by charcoal was investigated in the temperature range of 850 to 1100oC. A combination of sample weight loss measurements, exist gas analysis and chemical analysis of the reaction products was used to monitor the course of the reaction.The influence of temperature, charge porosity, relative amount of reactants and their particle size on the reduction rate was studied. Also considered was the effect the nature of the reduction caused by line addition to the charge. It was found that the cassiterite could be best reduced by a combination of high temperature, reasonably high temperature, reasonably high charcoal proportions, high charge porosity and the addition of a small percentage of lime.Based on the assumption rate controlling step was the reaction of carbon dioxide on the carbon surface, the kinetic data obtained from isothermal experiments was analysed and found consistent with the supposition. An activation energy of 60.8 kilocalories per mole was determined for the consumption of carbon by reaction with cassiterite. Associated with the main investigation were other experiments designed to provide supplementary information on the SnO2 + carbon reaction. These experiments involved the reduction of cassiterite by carbon monoxide in the temperature interval of 900 to 1100oC.The initial stages of the SnO2 + CO reaction were studied by means of change s in pH of a KOH absorbent solution into which the product gas was dissolved. Additional data was derived from sample weight loss determination at the end of the experiment, and chemical analysis of the reaction product.The prominence of the Boudouard reaction in the SnO2 + carbon reaction process was brought to light by these latter experiments. An activation energy of about 35.6 kilocalories per mole tin produced, was found for the SnO2 + CO reaction.
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