Analysis of the fluid dynamic behavior of the liquid and gas phases in reactors stirred with multiple hydrofoil impellers

Liquid- and gas-phase macromixing behavior was studied in gas-liquid high-a spect-ratio reactors stirred with multiple hydrofoil impellers pumping down ward. Water, a sodium sulfate solution, and poly(vinylpyrrolidone) solution s of viscosity up to 110 mPa.s were used as the liquid. For characterizing the Liquid phase, mixing time experiments were conducted at various operati ng conditions, while detecting the response curves at several positions ins ide the tank. Comparison of the experimental curves with the theoretical on es provided by simple fluid dynamic models showed that the axial dispersion model is quite acceptable. The influence of impeller speed, gas flow rate, and viscosity on the model parameter was studied, and dimensionless relati onships are given. The gas behavior was studied by means of the RTD and mod eled with the axial dispersion model, which proved good for water and accep table with coalescence-inhibiting electrolyte solutions. The model paramete r dependence on the operating conditions was studied. Comparison between hy drofoil impellers and radial Rushton turbines is also attempted.