Prediction of arc instability induced by arc-bath interaction in brush arc mode during electric smelting furnace operation

초록

With the growing demand for direct reduction in the steelmaking industry, the Electric Smelting Furnace (ESF) is considered a promising option for smelting Direct Reduced Iron (DRI) produced from lowgrade ore. Electric Smelting Furnace is expected to effectively manage the large volumes of slag generated during the process. Although the ESF is commonly operated in submerged arc mode for ferroalloy production, brush arc mode is considered necessary for DRI to supply sufficient heat to the smelter, given the relatively high electrical conductivity of slag anticipated in this process. In this work, a mathematical model has been developed to simulate the ESF process under brush arc operation. The model integrates multiphase flow, heat transfer, and Magnetohydrodynamics (MHD) to predict multiphysics, including Lorentz forces and Joule heating. This framework enables the prediction of critical features such as arc formation and corresponding Joule heating, flow patterns driven by the plasma jet, cavity formation, and arc instabilities. After validation against existing studies1), the model was applied to investigate arc instability under various operating conditions, including differences in arc length (e.g., long arc vs. brush arc) and bath type (e.g., iron vs. slag). Results revealed that brush arc mode exhibits unstable arc behavior irrespective of the bath type, in contrast to the more stable behavior observed in long arc mode2). Furthermore, distinct mechanisms of arc instability were identified, depending on the bath composition.