Effect of Hydrogen Addition on Reduction Kinetics of Iron Oxides in Gas-injection BF

Abstract

The gas-injection BF is a new iron-making technology with injecting gas instead of the traditional pulverized coal injection and recycling the BF top gas through the gasifier. Compare with traditional BF, there is a larger amount of reducing gas such as CO and H₂ in gas-injection BF. Effect of H₂ addition on reduction kinetics of iron oxides in gas-injection BF was investigated by Thermogravimetric Analysis. The result shows that the reduction rate of iron oxides rise with the increase in both temperature and H₂ content. By contrast with the H₂ content increasing from 10% to 15% at 700°C and 900°C, the improvement of reduction rate is more obvious when addition from 15% to 20% at the same temperature. For comparison, it shows an opposite result in the condition of 1000°C. In addition, the efficiency of H₂ on reduction rate can be neglected as the content is less than 5%. The reaction mechanism was obtained according to the unreacted core model. In the condition of 30% CO+10% H₂, both the diffusion rate and interfacial reaction rate reveal an increasing trend with the increase of temperature, of which the degree of improvement in diffusion rate is more significant, which leads to the interface reaction gradually being the controlling step. The same case occurs with the increase of H₂ at 900°C. Under the condition of experiment, the activation energy decreases with H₂ addition, which illustrates that the reduction of iron oxides become more easily to perform with the rich hydrogen in gas-injection BF.