Abstract

The stability of the operation in a submerged arc furnace is dependent on the electrical current paths in the process. The goal of this paper has been to better understand where the electric current runs through the ferromanganese furnace as a function of coke bed shape and size. Simulations of the current through a tri-electrode setup at a single point in time were done. The amount of electricity passing through various areas of the model was calculated using the modelling software “COMSOL multiphysics 5.0”. The simulations show a strong correlation between coke bed size and shape, and the electrical current concentration in the various paths of the FeMn-furnace. An almost linear proportionality between the total coke bed volume and the percentage of current flowing straight down to the metal, instead of through the sides, was found. The percentage went from above 95% for the smallest coke beds, to around 50% for the largest ones. The electrode tip position was shown to be dependent on the coke bed size and shape, generally sticking deeper into the coke in more narrow beds. The percentage of current going through the charge varies from below 1% to over 8%, while the heating effect generated through joule heating in the charge varies from about 1% to 9% of the total effect, both decreasing with larger coke beds. These numbers indicate that there is more joule heating in the charge than previously believed, especially in narrow coke beds.

Keywords: Coke beds; Materials; Electrode; Mn-ferroalloy