CHARACTERISATION OF BUBBLE BURSTING IN GAS/MOLTEN IRON SYSTEMS

摘要

A combined experimental and numerical approach has been used to investigate the mechanisms for the formation of splash resulting from gas injection in secondary steelmaking operations. Results from water modelling suggest that, for bubble diameters typical of bottom gas injection through porous plugs, splashed droplets are a consequence of the interaction between the surface of a melt and bubbles arriving at the surface. For gas bubbles with initial diameters less than approximately 10mm in water, droplets can result from rupture of the bubble cap that protrudes above the bath surface and break-up of a jet resulting from collapse of the bubble cavity. X-ray imaging of bubble behaviour in molten iron systems confirmed that the same mechanisms produce splashes in argon/molten iron systems despite the significant differences in fluid properties. Results from numerical simulations of bubble behaviour indicated that the collapse of a single bubble can be characterised by the Eotvos number and thus provide a link between conditions in low and high temperature systems. This result was combined with water modelling data to determine a critical Eotvos number for which ejections resulting from bubble collapse of a single bubble are a maximum. The existence of a critical Eotvos number is of practical importance since it provides a useful guide for identifying the conditions for dust and accretion formation in secondary steelmaking.