Measurement of reduction rate of hematite powder with CO-CO2 gas mixture by using thermobalance

The reduction rate of hematite powder (0.15mm in diameter) with CO-CO2 gas mixture was measured by a thermo-balance of which sensitivity was 1 mu g. The sample was put into a Pt-basket and the basket was suspended in a reaction tube from the balance. The weight of sample should be less than 0.2g in order to obtain the reduction rate of a single hematite particle accurately. The reduction rate was controlled by interface chemical reaction because the reduction product layer was porous. The chemical reaction rate constant kc was obtained at 600 degrees C-900 degrees C, The value of kc decreased with a rise of temperature because of sintering of hematite layer. The obtained value of he was applied to the analysis of fluidized bed reduction of hematite powder with CO-CO2 gas mixture. The calculated reduction curves agreed well with the measured ones by fluidized bed.