The campaign length of a blast furnace is usually limited by the hearth lining lifetime. In order to maximize the campaign length and ensure a good draining of hot metal and slag, a good understanding of the flow is essential. Challenges in modeling the flow involve several continuous phases (hot metal, slag and hot blast) as well as the presence of the deadman, a dense bed of coke particles which results in porous areas in the hearth. The shape and position of the deadman depend on the weight of the burden column above and the buoyancy forces from the liquid metal and slag in the hearth.
We present a numerical coupled CFD (Computational Fluid Dynamics) ? DEM (Discrete Element Method) model to account for the transient behavior of the deadman. A VOF (Volume of Fluid) method is used to model the multiple continuous phases and the DEM method to solve the particle ? particle interaction, to give an accurate representation of the porous areas. The VOF and DEM models are coupled together in a 2-way manner, resulting in a complete 4-way coupled CFD-DEM model. Experimental validation was performed on a small-scale particle filled tank. The tank was drained of the fluids through sitting and floating particle beds.
In general, good agreements were found between the simulations and experiments. The mass flow and fluid interfaces could successfully be reproduced in the simulations. However, issues due to artificial local pressure fluctuations in the particle bed were encountered. This effect is negligible for heavy particles (particle to fluid density ratios ~ 2,5) but for lighter particles (particle to fluid density ratios ~1.0) this causes stability issues.