Effect of Furnace Parameters on Optical Emission Spectra of Hematite Reduction by Hydrogen Plasma

Abstract Hydrogen plasma smelting reduction (HPSR) has been envisaged as a potential $$\text{CO}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>CO</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:math> -lean process for ore-based steelmaking, combining the reduction, melting and refining steps into a single unit process. However, scaling the process to industrial use still requires some work. In previous studies, optical emission spectroscopy (OES) has been suggested as a potential process monitoring method for HPSR. The present study investigates the effect of furnace parameters, such as the arc length and current, on the optical emissions of the hematite reduction by HPSR. To understand the effect of slag components, a few experiments were also conducted with fluxed hematite. It was found that the optical emissions of non-ionized elements are more intense at lower currents than at higher currents due to a lower level of ionization. The electron density calculated from the optical emissions could be used to estimate the arc length if the arc cannot be directly observed. It was also noted that the optical emissions of the slag components are very distinct in fluxed hematite experiments, which is of interest for potential industrial applications. Finally, the positioning of the optical fiber in relation to the plasma was found to be crucial for the successful monitoring of the experiments.