Transient 3D hydrodynamic model of a blast furnace main trough

Abstract

A transient 3D CFD model is solved to investigate the features of the complex flow in a blast furnace trough. Hot metal, slag, and air are considered as different phases of the flow. The influence of various taphole stream conditions on the hydrodynamics in the trough is examined, such as different slag-hot metal ratios, taphole diameters, and stream velocities. The special case of a dry trough during its first tapping is also addressed. Attention is devoted to the characterization of the wall shear stress, closely related to mechanical erosion, and to the evolution of the interfaces separating the fluid phases. Intricate flow patterns, characterized by large recirculations and return currents of both slag and hot metal, are observed. The simultaneous tapping of slag and hot metal leads to distinct flow features, deviating from the initial stage, when only hot metal is drained, as well as lower shear stress values, up to 31% less with increasing slag content in the taphole stream. Slag and hot metal levels in the trough evolve rapidly to quasi-steady states. Although the influence of the taphole stream velocity and diameter have a modest impact on the free surface dynamics, variations in the taphole slag fraction lead to significant fluctuations in the depth of slag and hot metal pools in the trough. The height of the slag-iron free surface can increase by up to 40% relative to its initial level, while the variation in the slag pool depth approaches 30%. These changes in the interface positions carry potential implications for refractory wear, as they suggest a substantial shift of the slag-hot metal line during each tapping.