Physical, chemical and thermal histories of an oxygen bubble in bath during bottom blown process

Abstract

A mathematic model has been developed for an oxygen bubble rising in metal during a bottom blown process. The model successfully coupled local reactions and mass transport with heat transport between metal and the bubble surface, and between the latter and the bubble interior. This novel method reveals the physical, chemical and thermal histories of an oxygen bubble during a bottom blown process. An oxygen bubble rising in Fe–3%C metal under conditions of the oxygen bottom blown process was described by the modelling. The results show (1) the heat supplied to the bath is sourced from the secondary combustion in the bubbles rather than from the decarburisation at a bubble surface; (2) the temperature of a bubble surface reached a maximum of few degrees higher than the bath at few centimetres above the nozzle; (3) the maximum heat supplied to the bath by a bubble midway along the bubble trajectory is much more than the total heat supplied by the bubble reaching the bath surface; (4) the energy in the process-off gas is as high as three-fold of that received by the bath; and (5) iron is unlikely to be oxidised in front of the nozzle.

Keywords:

• Kinetics
• Energy balance
• Decarburisation
• Steelmaking
• Melting
• Bottom blowing
• Bubble