Solid/liquid mixing pattern and its comparison with liquid/liquid one in a mechanically- stirred vessel

Solid/liquid mixing pattern was investigated and compared with the liquid/liquid one in a mechanically-stirred vessel. The cold model experiment was carried out to make clear the effect of operating factors such as volumetric ratio of solid particles to liquid, rotation speed, impeller position, etc. on the mixing pattern. The solid/liquid mixing pattern was observed visually and the vortex depth of solid/liquid or gas/liquid interface was measured with a ruler. It was categorized into 3 types as well as the liquid/liquid mixing pattern. I: the region where solid particles have no dispersion, II: the region where some of the solid particles disperse into liquid, III: the region where almost all of the solid particles disperse into liquid. The solid/liquid mixing pattern transits from I to II, and from II to III as the impeller depth decreased and the rotation speed increased. The transition of I-II shifted to a higher rotation speed in cases of smaller volumetric ratio of solid to liquid, larger particles diameter, larger density difference between solid-liquid and smaller liquid viscosity. The transition of II-III shifted to the higher rotation speed in cases of smaller impeller diameter and larger liquid viscosity, and showed independency on volumetric ratio of solid to liquid, particles diameter and density difference between solid and liquid. Multi regression analysis on the transition of I-II showed that the calculation agreed with the measurement. Dimensionless correlation equation on the transition of II-III also showed a good agreement between calculation and measurement and it was adaptable to liquid/liquid system.