Swelling Behavior of Iron Ore Pellets during Reduction in H<sub>2</sub> and N<sub>2</sub>/H<sub>2</sub> Atmospheres at Different Temperatures
Oleksandr Kovtun, Mykyta Levchenko, Erik Oldinski, Martin Gräbner, Olena Volkova
Abstract
The need to develop green steelmaking techniques has led to the replacement of reducing agents such as CO with H 2 . H 2 and N 2 /H 2 mixtures can be used for the carbothermal reduction of iron ore. Herein, the reduction swelling index (RSI) of iron ore pellets in a forming gas (N 2 /H 2 ) atmosphere at temperatures of 700–1000 °C is investigated and it is compared with that in pure H 2 . It is showed in the experimental results that the RSI increases with increasing temperature for both the H 2 and N 2 /H 2 atmospheres. The maximum swelling is reached approximately 5 min into the H 2 reduction process, while in the N 2 /H 2 atmosphere, it is reached after 25–45 min of reduction, depending on the temperature. When the reduction temperature exceeds 900 °C, the RSI is greater than 20%. Scanning electron microscopy/energy‐dispersive X‐ray spectroscopy is performed to detect the changes in the microstructure and chemical composition of the samples. The nonreduced areas in the reduced pellets during the N 2 /H 2 reduction process are analyzed using light optical microscopy.