| Interactions between slag,metal and gas phases are very common in the vessels of metallurgical process.Some bubbles pass through the slag–metal interface with molten steel entrainment and the steel droplets formed in the slag phase.While some bubbles aggregate at the slag–metal interface because of their sizes or other relative properties,when the bubbles flow up.The behavior of bubbles at the slag-metal interface changes the interaction morphology of slag–metal interface.And in turn,it significantly influences the slag–metal reaction,heat,mass transfer and finally the smelting process.The current paper mainly focuses on the bubbles that can pass through the slag layer.The effects of different physical parameters of bubbles and slag layer on entrainment amount of molten steel are studied by physical simulation and numerical simulation.In the physical simulation,the oil-water system was used to simulate the slag-metal system.,Mainly the influences of bubble size,oil density,and oil viscosity on the bubble entrainment were studied.The results showed that there were three entrainment situations when bubbles with different sizes passed through the oil-water interface.Only a small part of the water phase was drawn up to the oil phase.During the movement of the bubbles,the deformation is small and almost globose.The larger size bubbles pass through the oil-water entrained more water column at the interface.As the bubble raised,the suspended column grows to a certain extent and breaks.The broken part may adhere to the bubble and continue to rise,or break into droplets and fall back.The large bubble may deform to ellipsoidal or hat-shaped during the movement.The bubble rising velocity were affected by the size.the rising velocity of the smaller(d=8.09 mm)bubble tends to stabilize at 200mm/s after a rapidly velocity increasing at the initial stage.For the larger bubble(d=10.33 mm,d=11.67 mm),a minimum velocity of 170 mm/s,and a maximum velocity of 295 mm/s can be obtained.Moreover,it was found that the bubble entrainment amount increased by 787%when the bubble equivalent diameter increased from 0.809 mm to 1.26 mm in the study of the influence of bubble size,oil layer density,and oil layer viscosity on the entrainment amount.And the bubble entrainment amount increased with the bubble size and oil density increasing,while decreased with the increasing of oil viscosity.All trends mentioned above are not obvious when the bubble size is small.It would be significant when the bubble size increases.Numerical modellings were built to study the effect of bubble diameter,slag density,slag viscosity,slag-metal interfacial tension on bubble entrainment.It is found that the rise of bubbles in the slag-metal system can be roughly divided into four stages:bubbles rise from the bath bottom,the bubbles drain the molten steel into the slag layer,the bubbles continue to rise and bring up the molten steel,and the bubbles separate from the molten steel.The simulation results are similar to that of the physical simulations,indicating that numerical modelling is receivable to describe the bubble entrainment phenomena for real slag–metal system.It is found that the he entrainment amount increased by 741%when the initial bubble diameter increased from 1 cm to 1.6 cm.The entrainment amount increased by 62.34%when the density of the slag increased from 2000 kg/m~3to 5000 kg/m~3and the entrainment amount increased with increasing of the slag density.The entrainment is reduced by30.56%,when the slag-metal interfacial tension increased by 0.65 N/m As large as1.1 N/m,and the entrainment amount decreased with increasing the slag-metal interfacial tension.In addition,it is found that the entrainment increased slightly when increased the slag viscosity from 0.01 Pa·s to 0.08 Pa·s.the entrainment amount is reduced by 18.4%when the slag viscosity increased from 0.05 Pa·s to 2Pa·s.Moreover,the time for the bubble separating from molten steel increased and the entrainment decreased as the slag viscosity increased. |
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