Combining Optical Emission Spectroscopy and Filtered Video Imaging to Study Visually Observable Events in Hydrogen Plasma Smelting Reduction of Magnetite

Abstract With the goal of reaching CO 2 neutrality in the following decades, the hydrogen plasma smelting reduction (HPSR) offers a possible route to advance the decarbonization of the steel industry. In recent years, increasing efforts have been made to optimize this process, and with encouraging results from electric arc furnaces (EAF), optical emission spectroscopy (OES) is rising as a useful tool for online analysis. This study investigates the use of OES in combination with filtered video imaging to study the relationship between optical emission spectra and the spatial changes in brightness within the reducing plasma inside an HPSR reactor. With the selected bandpass filters, combining the videos and OES spectra allowed to address the optical emissions from atomic iron, manganese, magnesium, sodium, and hydrogen during HPSR of magnetite samples. A strong correlation was observed between the brightness of the plasma’s outer shell and the intensity of the OES spectra. These insights are relevant for HPSR process control, as increased material evaporation—especially of iron—can lead to material losses.