Large Electrode Movements: Realistic Electrical Crater Models

The operation of silicon submerged-arc furnaces is sometimes vexed by large, comparatively rapid electrode movements on the order of one meter in about one hour. The physical origin of such extreme electrode movements is still unclear, as is the question of how the current or resistance can stay more or less constant despite such a large change of the position of the electrode tip. Finite-element models of the furnaces’ electrical conditions usually either assign a constant conductivity to the crater gas or employ predefined high-conductivity regions that simulate the electrical arcs. As such, present models are ill equipped to handle large electrode movements and the continuous rearrangement of the arc positions. This paper presents a new approach to crater modeling, in which the crater-gas conductivity depends on the distance between the electrode surface and the crater wall. Combined with more realistic crater geometries, this enables pragmatic estimates to be made for the accessible current paths, and further makes it possible to winnow the candidate mechanisms behind large electrode movements from the long list of suggestions available in the literature and in the industry.