STEEL FLOW CHARACTERISTICS IN CFD IMPROVED EAF BOTTOM TAPPING SYSTEMS

摘要

The steel flow characteristics in electric arc furnace (EAF) bottom tapping systems were investigated using computational fluid dynamics (CFD) simulations for a large variety of tap channel geometries and four different EAFs. The results clearly demonstrated the advantages of a new conical tap channel design compared to the conventional cylindrical geometries, since for the same tap diameter the resulting mass flow rate was increased providing shorter tap-to-tap times. In addition, backflow with negative pressure patterns in the channel entry area was completely avoided with the conical design. Consequently, the steel flow turbulence intensity was significantly decreased resulting in a more stable steel jet during tapping. The maximum steel velocity and velocity gradients at the channel entry and the pressure differences at the channel walls were significantly decreased indicating a lower tendency for wear at the channel entry area and, therefore, an increased lifetime. Typically, approaches to increase productivity and decrease tap-to-tap times have increased the tap diameter. However, the CFD simulations demonstrated that increasing the tap diameter resulted in earlier slag entrainment and an increased steel mass remaining in the EAF. Thereby, the yield was decreased for large tap diameters, although the tapping time may be decreased due to the higher mass flux. However, due to the desired late slag entrainment at maximum mass flux, selection of an appropriate conical tapping system maximizes tapping efficiency.