(70bm) Floating Solid Dispersion in an Agitated Vessel:The Effect of Impeller Location

The basic motivation for the present work is to investigate capability of the agitated system provided with multiple impellers on the suspension of floating solid material in liquid. The effect of off-bottom impeller clearance as well as the spacing between impellers on the minimum impeller speed for complete solid suspension, power consumption and axial concentration profiles were investigated in single and double-impeller system using four-straight blade turbines (SBT). Experiments were performed in cylindrical flat bottom vessel with internal diameter of 0.30 m. Tap water and polyethylene particles (PEHD) were used as liquid and solid phase, respectively. The critical impeller speed for the complete suspension of floating solid particles, NJS, was determined using Joosten visual method, while power consumption was measured using torque meters produced by S. Himmelstein and Company. The local solids concentration from a slurry mixing tank have been measured by the withdrawal of sample from the vessel. On the basis of the experimental results it was observed that the presence of additional (second) impeller actually produced the reduction in the power consumption as well as decrease of the minimum impeller speed for the complete suspension of floating solid particles, NJS. The obtained results are strong function of the flow patterns structure created by impeller configuration applied. Flow patterns in mixing vessel was studied by visual observation using digital camera. Support for these observations was derived flow characteristics studied using VisiMix 2000 Turbulent.