Induced Currents in the Lining and Steel Shell of Submerged Arc Furnaces

Numerical models in 2D and 3D are used to study induced currents in the lining and steel shell of large three-phase submerged arc furnaces. The alternating currents supplied through the electrodes cause a significant amount of induced power in the furnace lining and shell. The induced currents flow in three large loops with an accumulation of current near the top of the steel shell between the electrodes. The net result is a thermal loss with heat dissipated at the surface. Furthermore, such accumulation may cause potentially damaging hot spots in the steel. If this persists over a long time, the shell may thin and deteriorate and, in worst-case scenarios, the shell may be cracked or punctured. The influence of an electrically conducting lining and the effect of subdividing the shell in insulated sections have been studied. It is shown that an electrically conducting lining will have a significant shielding effect on the steel shell. The induced currents are considerably reduced in the steel, and "pushed into " the lining. The size of current loops in the shell can be restricted by subdividing the steel into sections with insulation between each section. Such modification is detrimental. Strong opposing currents will be formed on each side of the insulating gaps, leading to higher current concentrations and increasing the risk of hot spots on the steel shell. In addition, the heat loss due to induced currents in the steel will be enhanced. [GRAPHICS]