The reduction processes of sintered ore in the fixed bed with CO gas have been studied.
The reduction rates of sintered ore in the temperature range from 800 to 1000℃ have been measured by analysing the waste gas composition or by weighing the bed weight continuously ; the following results are obtained.
(1) The reduction curves obtained by gas analysis are in good agreement with those by the thermobalance in the same experimental conditions.
(2) At a constant ratio of the bed weight to the gas flow rate (M/V), the same reduction curves were obtained at different gas flow rates (4.6, 9.1 and 36 Nl/min) ; the gas film resistance seems to be unimportant.
(3) The analysis based on the unreacted core model for a single pellet applied to the reduction of sintered ore with CO gas gives the following expression for the calculated chemical reaction rate constant ks=exp(5.23-14000/RT). As the calculated constant F defind as r0ks/De is dependent of the diameter of sintered ore, it is considered that the reduction process is controlled by the chemical reaction rate for small sizes (Dp=3 mm), but is controlled by mixed rates of the chemical reaction and the gas diffusion through ash layer for large sizes (Dp=7-13 mm).
