Intensification of Bubble Disintegration and Dispersion by Mechanical Stirring in Gas Injection Refining
Yan Liu, Masamichi Sano, TingAn Zhang, Qiang Wang, JiCheng He
Water model experiments were performed for developing highly efficient gas injection refining processes. Mechanical stirring was applied to disintegrate the injected bubbles and to disperse them widely in the bath. The bubble disintegration and dispersion were investigated by changing rotation mode (direction of rotation), rotation speed and blade size of the impeller, and gas flow rate. Forward rotation of the impeller induced a stable tangential flow and could not disperse bubbles in the bath due to formation of a vortex around the impeller shaft. The tangential flow was suppressed by forward-interrupt rotation, which could reduce the vortex formation to some degree. However, the forward-interrupt rotation could not disperse the bubbles widely in the bath. Forward–reverse rotation could prevent the vortex formation completely and create a turbulent and strong shear stress field, which intensified the bubble disintegration and dispersion in the bath. Higher impeller rotation speed and larger blade length in the forward–reverse rotation could enhance the bubble disintegration more intensely, and make the dispersed bubbles smaller and the bubble dispersion zone wider. The bubble size tended to be larger at higher gas flow rates. However, its dependence on the gas flow rate became smaller at higher impeller rotation speed.
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