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 thermobalance of which sensitivity was 1μg. 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°C-900°C. The value of kc decreased with a rise of temperature because of sintering of hematite layer. The obtained value of kc 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.