In the pursuit of cleaner and more sustainable steel production methods, innovative approaches such as Direct Reduction of Iron by Hydrogen (DRI) have emerged. However, these advancements also present unique challenges. While DRI can be effectively melted in an Electric Arc Furnace (EAF), this requires high grade ores and extensive secondary metallurgy processes. Alternatively, Submerged Arc Furnaces (SAFs) offer a promising avenue for producing high-quality steel from BF grade ores while adhering to the Basic Oxygen Furnace (BOF) route.
SAFs operate similarly to EAFs, albeit with a critical distinction: the arc is submerged within a thick layer of liquid slag. Consequently, heat transfer in SAFs differs substantially, as radiation from the arc is replaced by Joule heating within the slag. Efficiently transferring this heat to the liquid metal beneath the slag layer poses a significant challenge. Molecular conduction is inherently slow and insufficient for achieving economically viable production rates. Thus, convective heat transfer becomes paramount. However, buoyancy-driven flow within the furnace is typically weak, imposing limitations on the heat exchange between the heat source and the liquid metal.
In tackling such challenges, a deeper comprehension of the flow dynamics and associated phenomena within SAFs becomes imperative. Numerical modeling stands out as a pivotal tool in unraveling the effects various parameters exert on thermal energy transfer within these environments. The development of such a model necessitates rigorous validation.
Validation from industrial processes is extremely difficult, due to harsh conditions in the furnace. Thus, water models are an invaluable resource for validation purposes. To this end, a physical model containing water and oil, mimicking the properties of hot metal and slag, respectively, is designed and constructed. Within this setup, a constant temperature heater with two concentric coils is submerged in the oil while local cooling is applied to mimic heat losses.
Particle Image Velocimetry (PIV) is employed to investigate the buoyancy-driven flow field within the water. Multiple thermocouples are placed in the water and the oil to record temperature variations over time. Additionally, thermocouples are also placed in the air above the oil.
Throughout a series of experiments, two key parameters – heater temperature and water height – are independently varied to discern their effects on the system. Concurrently, Computational Fluid Dynamics (CFD) simulations are executed. The laminar nature of the flow poses inherent challenges to numerical simulations. Factors such as low diffusivity and the presence of multiple phases make the thermal energy conservation challenging. While the temperature profile exhibits close agreement with experimental data, further refinement is warranted to enhance the accuracy of the velocity field.
By elucidating the intricate dynamics of heat transfer within the water-oil system representative of SAFs, this work contributes significantly to the understanding of steel production methodologies.