Quantitative Impact of Hydrogen on Voltage Characteristics and Arc Stability in Industrial EAFs and HPSR

The introduction of hydrogen in Electric arc furnaces (EAF) operations (mainly by replacing natural gas by hydrogen as fuel for furnace burners) and other hydrogen plasma technologies, such as Hydrogen plasma smelter reduction (HPSR), presents complex challenges related to arc stability. This study introduces a three-dimensional, transient numerical model to investigate the electric arc behaviour for both atmospheric air and hydrogen environments. The arc is operated at a fixed current of 1 kA between two solid electrodes with a 15 cm gap. The model simultaneously solves compressible flow, thermal, and electromagnetic fields to analyse the arc dynamics, temperature distribution, and voltage drop across the arc. The model highlights the importance of compressibility, which impacts the flow and thermal fields, thereby affecting the voltage drop predicted in the arc. Moreover, the study investigates the instabilities originating near cathode spot and explains the intrinsic unstable nature of long, high current density arcs. The arc operating in compressible hydrogen exhibits faster plasma jet and more rapid, pronounced instabilities compared to the arc in air. The voltage drop in hydrogen averages around 334 V, 79 V higher than in air 255 V. Additionally, the voltage drop in hydrogen possesses a higher frequency and more frequent extreme events when compared to the voltage drop in air. This is attributed to the distinctive thermophysical properties of hydrogen, which make it highly reactive and challenging to stabilize the arc. This study aims to explain hydrogen plasma properties and contribute to better control of new hydrogen-based technologies in metallurgy.