Effect of Swirl Motion on Mixing Time in Water Bath Agitated by Upward Gas Injection

Mixing time in a cylindrical water bath agitated by upward gas injection through a single-hole bottom nozzle and a J-shaped top lance was experimentally investigated in the presence of swirl motion of the bath. This gas injection process is regarded as one of models for steel refining processes. Measured values of the mixing time could not be predicted by empirical equations derived previously in the absence of the swirl motion. The effect of the swirl motion on the mixing time was significant, i.e., the mixing time was highly shortened in the presence of the swirl motion. An empirical equation was newly proposed for the mixing time as a function of the injection distance from the nozzle tip to the bath surface, gas flow rate, bath diameter, bath depth, and kinematic viscosity of liquid.