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Abstract
Stable and efficient operation of an Ironmaking Blast Furnace is driven by control of furnace permeability, particularly in the cohesive zone where ferrous materials undergo softening and melting. Due to the difficulty in replicating the conditions in experimental studies, numerical simulation is vital to building understanding of the behaviour of material in the cohesive zone and the effects on the overall permeability in the furnace. Whilst there have been significant attempts to simulate liquids flow, and effects on gas and solid distribution around the cohesive zone, there has been little consideration of how particle deformation during softeningâ melting affects cohesive zone permeability.
This study developed a numerical model capable of simulating the change of shape experienced by particles as they undergo deformation within the cohesive zone. A subâ particle Discrete Element Model framework was chosen where an agglomeration of subâ particles represents a single deformable macroâ particle. Rearrangement of the subâ particles permits deformation of the macroâ particle.
Sensitivity of deformation characteristics to model parameters was studied in two systems compression of a single spherical agglomerate and tensile extension of a cylindrical sample. Simulations with brittle and ductile conditions showed that multiple parameters impacted on the deformation behaviour of material.
Simulations of the deformation under load of a packed bed were conducted and compared to previous experimental results. The numerical simulation was able to reproduce broadly the deformation of particles within the packed bed; however lack of a creep mechanism limited the accuracy of the time dependent response. Direct analysis of the contact areas between deforming particles provided useful information regarding the behaviour of softening particles under load.
Finally, the model was applied to simulate an industrial scale softeningâ melting test, in which hot reducing gas is passed through a bed of iron ore particles sandwiched between layers of coke particles. Localised porosities within the packed bed, as well as the condition of the softening particles, were used to calculate the pressure drop of the gas passing through the bed. This pressure drop was comparable to the experimental results. Channelling effects at lower porosity levels was also investigated and shown to have an influence on the understanding of the pressure drop within a deformable packed bed.