Modeling of a DC electric arc furnace -: Mixing in the bath

A mathematical model was developed to describe fluid flow, heat transfer and electromagnetic phenomena in the bath region of a Direct Current Electric Arc Furnace (DC-EAF). The different effects on the steel bath from the arc, a layer of slag on the top of the steel, and the injection of argon gas from the bottom, are represented using three different numeric approaches and analyzed in terms of fluid flow, heat transfer, and temperature stratification in the steel bath. Additionally, a sensitivity analysis was performed to explore the effect of the main process parameters and design variables of the process, such as furnace dimensions, arc conditions, and anode configurations. It was found that in the absence of gas injection, the electromagnetic body forces dominate the fluid flow in the bath region overcoming the opposite effects of buoyancy and shear from the arc. Injection of gases homogenizes the melt improving mixing, while the effect of the slag is to decrease mixing in the bath. Regarding the process analysis, the model showed that the best mixing and the best energy optimization from the arc are achieved when the geometry of the furnace presents the highest aspect ratio. Similarly, short arc lengths and high arc currents are beneficial for mixing. However, these improvements in mixing could be detrimental for the bottom refractory of the furnace because of the direct exposure of the hot metal coming from the arc attachment zone at the bottom wall. Then, the anode configuration can be designed to avoid excessive damage to the refractory.