Investigation of kinetics of coal based reduction of oolitic iron ore

Abstract

An oolitic iron ore was isothermally reduced by coal at 1423–1573 K, and the reduction kinetics was investigated in detail. The degree of reduction and reduction rate increased with increasing temperature and C/O molar ratio to some extent at the same reduction time. In the entire reduction process, the reduction mechanism changes with changing experimental conditions. The degree of reduction under different experimental conditions should be represented by different reduction kinetic models. The reduction rate curves are similar in shape and could be analytically divided into initial, intermediate and final stages. The apparent activation energies of the three stages are 48·26, 69·80 and 127·58 kJ mol⁻¹ respectively. The rate controlling mechanism in the reduction process was determined by analysing the reduction process and apparent activation energy. The rate controlling steps of these stages are combined gas diffusion and interfacial chemical reaction, surface chemical reaction and combined solid state diffusion and boundary reaction.

Keywords:

• Reduction kinetics
• Reducible oxygen
• Degree of reduction
• Reduction rate
• Oolitic iron ore
• Coal based reduction

Acknowledgement

The authors gratefully acknowledge the National Natural Science Foundation of China for funding this research (grant no. 51134002).