Study on the controlling steps and reduction kinetics of iron oxide briquettes with CO-H-2 mixtures

摘要

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 H-2/CO (0:100, 25:75, 50:50, 75:25, 100:0) and temperatures (800 degrees C, 900 degrees C, 1000 degrees 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 degrees C and 900 degrees C. Both the increase of temperature and the H-2 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.