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Kinetics of reduction of titaniferous ores with lignite coal Sucre-García, Gustavo A.


An inductively heated rotary reactor has been used to study the reduction kinetics of Westport and Florida ilmenites, and Glenbrook iron-sands with Saskatchewan lignite coal. The effect of speed of rotation, char to ore ratio, temperature, and pre-oxidation on the reduction behaviour was examined, and the reaction rate followed by gas analysis and flow measurement. Independent activation energies have been determined; for the reduction of Westport and Florida ilmenites the values were 25 and 7.5 Kcal/mole respectively, while Glenbrook ironsands and pre-oxidized West-port ore showed a change from 25 to 7.5 Kcal/mole due to a change in the rate controlling step. For the Boudouard reaction the activation energy was 55 Kcal/mole. Ore reducibilities (in cm³/g.s) have been calculated to be 4 x 10⁵ for Westport ore; 4 x 10³ for Florida ilmenite; 2 x 10⁶ and 2 x 10³ for pre-oxidized ore; and 9 x 10⁴ and 8 x 10¹ for Glenbrook ironsands; in the last two cases the two values given correspond to the two activation energies specified above. Char reactivity has been found to be 2 x 10¹¹ cm³/g.s. The reduction mechanism has been shown to be very sensitive to the ore type and temperature. In general, a mixed control between the reduction and gasification reactions was observed below 1000°C. Mixed control also existed during the reduction of pre-oxidized and Florida ores at 1050°C until 75% reduction; above this reduction level the reduction reaction limited the process which was also the case of Westport and Glenbrook ores at this temperature. The Boudouard reaction was found to govern the overall rate only during the reduction of Florida ilmenite at 950°C below 45% reduction.

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