Energy efficient solutions of DC Electric Arc Furnace Bottom Electrode
Keywords:DC electric arc furnace, electrovortex flows, bottom electrode, phase transition, copper-steel transition zone, energy efficiency
Analysis of recent research and publications. The problems of thermal state of billet-type bottom electrode (BE) in liquid bath of DC electric arc furnace (EAF) are associated with limited thermal conductivity of the rod in the absence of available alternative to copper-steel pair. There isn’t enough data on values of convective and Joule components of heat flux, passing through BE, initiated by electrovortex flows (EVF); regarding influence of thermophysical characteristics of transition copper-steel zone and cooling rate of BE copper part on the position of phase transition surface of steel part. Problems are considered, especially related to innovative “flat bath” steelmaking technologies, in which the possibilities of dead time pauses for periodic renewal of the BE body due to “EVF-off” are significantly limited.
Purpose. To investigate the effect of EVT on the thermal state of bottom electrode and to develop on this base the energy efficient BE solutions.
Methodology. Numerical simulations of BE thermal state and an industrial testing of essentials.
Findings & Originality. For the first time, the joint effect of EVF, Joule heat, and characteristics of BE transition zone copper – steel on the position and equilibrium thickness of solid steel part of the BE, which determines the energy efficiency of DC EAF operation, was comprehensively studied.
Research implications. Numerical simulations of EVF in DC EAF steelmaking bath and heat transfer with a phase transition through BE were carried out. The heat flux density and local EVF velocity in anode well are 1.8–2 MW/m2 and 0.75 m/s, respectively. Equilibrium thickness of solid steel BE part is critically dependent on the width of copper-steel transition zone, should not exceed 20-25 mm. Contribution of Joule component of total thermal load on the BE does not exceed 20%. Intensification of cooling rate above ≥ 20 kW/(m2K) practically doesn’t affect the BE solid steel part thickness.
Practical implications. Manufacturing technology of BE with a narrow transition zone by the method of two-stage electro-slag welding of copper on a steel billet, which ensures stable DC EAF operation and increases energy efficiency, has been improved.
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