Regular Article

Study on the controlling steps and reduction kinetics of iron oxide briquettes with CO-H₂ mixtures

School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China

^* Email: wxz_ustb@163.com

Received: 29 March 2017
Received in final form: 3 July 2017
Accepted: 8 September 2017

Abstract

Hydrogen has a better reducibility than CO and the products are environment-friendly, which is expected to substitute carbon in ironmaking process to reduce greenhouse gas emissions. In this paper, the reduction dynamitic characteristics of briquettes were studied under the molar ratios of H₂/CO (0:100, 25:75, 50:50, 75:25, 100:0) and temperatures (800 °C, 900 °C, 1000 °C). The results showed that the reaction rate increased with the rise of temperature or hydrogen content. Based on experimental results, the reduction of the iron oxide briquettes was divided into two stages according to the controlling step. In the former stage, the reaction was controlled by the interfacial chemical reaction. In the final stage, it was shafted to internal diffusion and mixed control at 800 °C and 900 °C. Both the increase of temperature and the H₂ ratio in the atmosphere contributed to improve the range controlled by interfacial chemical reaction during the reduction process. In addition, the apparent activation energy was increased with the increase of hydrogen content from 48.64 kJ/mol to 63.19 kJ/mol.