Liquid homogenization in aerated multi-impeller stirred vessel

The macroflow of fluid in a tall cylindrical vessel stirred with multiple s tirrers was studied in the case of aeration of a liquid charge. The time of homogenization of the charge (mixing time) was calculated from the time de pendency of the tracer concentration measured at various locations. Two typ es of stirrer were used in the experiments: six-bladed Rushton turbines and /or pitched-blade turbines with inclined blades pumping the liquid down or up. Four stirrers of the same type were located on the shaft. Other variabl es during the experiments were the stirrer frequency and the gas flow rate. It was found that the liquid macroflow in the vessel could be interpreted by the cell model or by the axial dispersion model for unaerated as well as for aerated systems. The influence of the aeration on the macroflow and mi xing time was explained by the interaction of buoyancy and radial forces, a nd equations for the model parameters were proposed containing gas flow num bers and Froude numbers.