Twin-electrode DC smelting furnaces—Theory and photographic testwork

Abstract

Use of twin-electrode DC arc furnaces for the purposes of smelting is a growing trend in the research being performed at Mintek. Even though twin-electrode furnaces add complexity to aspects of the mechanical design of the furnace roof and electrode mechanisms (as well as power supply configurations and control systems), the design and operational advantages gained in moving to dual electrodes are significant. Some small-scale testwork on a twin-electrode furnace was performed at Mintek in late 2003, with the aim of enabling direct observation of the plasma arcs and their interactions both with each other and the molten slag bath beneath them. Still and video photography of the twin arcs was performed. The results are presented here, along with some theoretical exploration. The arc trajectory is shown to follow a circular path, with the radius of curvature being directly proportional to the electrode separation, and approximately independent of electrical variables such as current. The influence of the arc deflection on the true arc length, and the dependence of arc voltage on electrode height have been calculated.