Selecting the Right Electrode Diameter for AC EAFs

by Patrice Boulanger, Claus Friedrich, Hagen Fuchs

Publisher - SGL Carbon GMBH, Canada

Category - General Novel

Over the past years, SGL Carbon has developed a modelling tool to precisely calculate graphite electrode consumption in electric arc furnaces. In this paper, we highlight some model basics and several applications where we complied with customer inquiries regarding various changes in EAF operation. During the past two years, discussions at Stahl-Zentrum’s seminar ‚Electrical engineering of arc furnaces‘ indicated a focus on high power AC-EAF’s with increased productivity through increased active power, leading to shorter power on- and tap to tap times, but requiring increased current levels1 . Therefore larger electrodes for slightly higher current densities are needed. As this occurs frequently after furnace or transformer revamps, customers ask for prediction of electrode performance under the new operating conditions. In these cases SGL Carbon voluntarily applies a performance model to consult customers. The performance model was developed during the past years, it is nowadays based on world-wide furnace operating data, combined with some physical basics and few numerical fits. It’s overall accuracy goes beyond most other models known from the literature2 . The model displays the shares of consumption mechanisms that contribute to net consumption, i.e. excluding breakages: • Sublimation at the tip is mainly influenced by secondary current. • Oxidation on both tip and conical surface is mainly influenced by electrode diameter, tap to tap time and oxygen input through burners and lances. • Stub end losses arise from temperature gradients and thermo-mechanical stress, and are therefore strongly influenced by current density.

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