(426b) Micromixing Characterization through Competitive Parallel Reactions in a Vessel Agitated by a Primary Impeller and a High Shear Homogenizer

Many mixing systems commonly used in the chemical and pharmaceutical industries are equipped with a primary impeller, to promote overall mixing and bulk flow, as well as an additional high-shear homogenizer to generate a high shear zone that enhances shear-sensitive processes, such as emulsification and dispersion, which may be conducted in the tank. The system used in this work was a fully baffled stirred vessel equipped with a disk turbine as the primary impeller and a high-speed rotor-stator homogenizer. The system's micromixing efficiency was experimentally characterized by means of competitive parallel reactions (Bourne reaction), where the yield of formation of one of the secondary product that is directly related to micromixing effects was experimentally measured. Process variables such as primary impeller speed and high shear homogenizer speed were varied and their effect on the local micromixing was quantified. In addition, the outcome of the reactions was tested for different scales as well as different reactant feed locations. The experimental data were also analyzed based on the results obtained from CFD simulations, aimed at determining the dependence of the product yield on the local energy dissipation in the feed region of the tank. The data obtained show that the additional mixing effects generated by the homogenizer produce a significant reduction in the yield of the by-product obtained when only the primary impeller is at work. In addition, the experimental results show that the speed of the primary impeller, speed of the homogenizer, tank volume, and injection location also affect the yield of the by-product. A relationship was found between the local energy dissipation rate at the injection location and the micromixing-dependent yield of the secondary by-product.