2002 Volume 88 Issue 12 Pages 815-822
Mixing time in a cylindrical water bath agitated by downward gas injection through a single-hole nozzle was experimentally investigated as a model study for steel refining processes. Measured values of the mixing time could not be predicted by empirical equations derived previously for bottom gas injection. The reason is that the bubble dispersion pattern caused by downward gas injection is much different from that by upward gas injection. An empirical equation for the mixing time was proposed as a function of the nozzle diameter, bath diameter, bath depth, nozzle position in the bath and gas flow rate. The measured values of the mixing time were approximated by this equation within a scatter of ±40%. This equation was also compared with the existing measured values and empirical equations to clarify the difference between upward and downward gas injection processes.