Micromixing Characteristics in a Stirred Tank with Multiple Impellers

The product distribution of competitive reactions in an agitated reactor is significantly affected by micromixing. A pair of competitive parallel test reactions were used to investigate the micromixing in a stirred tank of 0.476 m diameter with multiple impellers. One triple 3-narrow blade hydrofoil CBY impeller agitator and combination of one 6-hollow blade disk turbine HD-6 as bottom impeller with two CBY impellers were used in the experiments. The effects of feeding time, impeller speed, feeding location and agitator type on product distribution were systematically studied. For the multiple impeller systems, the product distribution is dominated by the impeller closest to the feeding location. The simplified micromixing model, the engulfment model, was used to predict the product distributions of triple CBY impellers. Good agreement can be found between the results predicted by the engulfment model and the experimental data. The results are of importance to the optimum design of multiple impeller industrial stirred reactors for fast complex reactions.