Cylindrical tap holes used for bottom tapping showed its potential for almost two decades as an alternative to the spout system in electric arc furnace (EAF). Its market share increased very fast as a result of the proven advantages like lower heat losses, controllable slag carry-over, more consistent flow, less refractory consumption and less tapping time. However, as a target for further improvements in the widely applied bottom tapping system, an optimization to the tap hole geometry at RHI using computational fluid dynamics (CFD) simulation was carried out. A conical tap hole design showed principally better results with respect to the cylindrical tap hole. By replacing the cylindrical design with the conical design at the same outlet diameter, a higher mass flow rate (less tapping time) and less stream turbulence intensity (longer life time) were attained.