High-speed imaging and electrical diagnostics of interacting arcs in dual-cathode electric arc furnace

Summary form only given. Electric arc furnaces (EAFs) are ubiquitous in the steelmaking industry, and find an increasing number of applications in municipal solid waste gasification and resource (energy and material) recovery from industrial wastes (e.g. recovery from mining residues). The dual-cathode configuration is used to form two individual arcs with a common anode, which contains the material under treatment. A multi-cathode arrangement enables different heat load patterns on the anode and more flexibility in the operating conditions. Such system is also the host of complex arc interactions through the Lorentz force. At short cathode tip-to-anode distances, two relatively independent arcs are formed in the dual-cathode configuration. As the arcs are elongated, partial merging of the arcs at the anode occurs, and a complete merging on the anode takes place at large gaps. Complex and intermittent arc patterns form with their associated voltage and current signatures. In this contribution we describe the distinct arc structures and corresponding voltage/current signatures that occur in a dual-cathode DC EAF using graphite electrodes and argon as the working gas. A 5 kHz synchronized data acquisition system for voltage, current and high-speed imaging was used to observe the arcs' dynamics and the resulting voltage and current signature. An image processing code was developed to measure the length of the arcs and to identify arc structure on each frame captured. The algorithm first locates the arcs' attachment points on the electrodes and then Dijkstra's shortest path algorithm is used to reconstruct the path of highest brightness between the anode and cathode attachment points. Preliminary experimental observations and image analyses revealed the existence of four different arc structures. We report on the possibility of distinguishing these four structures by analyzing the voltage and current signals.