Multiphase flow and interface dynamics in a blast furnace hearth: Effects of slag viscosity and coke diameter

Abstract

This study numerically investigates the effects of slag viscosity (${\mu }_s$) and coke diameter ($D_P$) on the behavior of gas-slag and slag-iron interfaces, as well as the mass flow rates of slag and iron, in a three-dimensional (3D) full-scale blast furnace hearth model with four tapholes undergoing tapping and plugging cycles. This study introduces new perspectives by focusing on the bifurcation behavior of interface evolution, the classification of two distinct regimes in temporal levels, and circumferential variations in interface dynamics along the side wall. The slag-iron interface exhibited linear descent followed by saturation, while the gas-slag interface underwent linear descent followed by acceleration. Bifurcation at the onset of slag drainage, occurring earlier with larger $D_P$and lower ${\mu }_s$, marked a critical shift in dynamics. Before bifurcation, $D_P$governed interface descent; after bifurcation, ${\mu }_s$dominated, lowering pressure and increasing the pressure gradient near the taphole. These findings include novel insights into localized dynamics, revealing sharper circumferential gradients under conditions of higher ${\mu }_s$and smaller $D_P$. Despite variations, slag and iron layer thickness ratios remained stable, reflecting their independence from ${\mu }_s$and $D_P$. Additionally, a critical intersection point in mass flow rates was identified, where slag flow surpassed iron flow. This point, delayed under conditions of higher ${\mu }_s$and smaller $D_P$, highlighted the influence of reduced fluidity on two-phase outflow dynamics. These findings highlight the potential of optimizing ${\mu }_s$and $D_P$to enhance fluidity, production, energy efficiency and sustainability in blast furnace operations.