Establishment of a Method for Precisely Controlling Mixing/Reaction in Stirred Vessels Utilizing Dynamic Changes of Flow Patterns

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This research project focused on dynamic changes of flow patterns in stirred vessels and aimed to establish of a method for precisely controlling mixing and/or reaction utilizing these phenomena from engineering aspect. Characteristics of mixing and particle dispersion in cylindrical and Conical Taylor vortex flow systems were investigated as a model for secondary circulating flow in a stirred vessel. At low Reynolds numbers, the fluid flowing near the vortex cell boundary was axially well-mixed, while the fluid element confined to the vortex core region poorly exchanged with the outer well-mixed flow region. Particle classification phenomena were also observed in Taylor vortex flow. The larger particle ranging from 50 to 80 μm could be seen in the outer region of vortex, while the smaller particles ranging from 20 to 50 mm were mainly observed in the vortex core region. We proposed a new particle classification device by combining these mixing and particle dispersion characteristics. … More In a conventional stirred vessel with Rushton turbine impeller, When the ratio of the impeller off-bottom clearance, C, to the tank inner diameter, T, is larger than 0.143 (C/T>0.143), the discharged stream was directed horizontally towards the walls whre it split into two streams that moved upwards and downwards generating two vortices (a double-loop pattrn). On the other hand, when C/T>0.143, the discharged stream moved downwards the bottom of vessel owing to the Coinda effect and then continued upwards to generate a strong vortex (a single-loop pattern). No transitional time-dependent flow state from a single to double-loop pattern could be seen at low Reynolds numbers. In future work, we will try to produce the transitional flow state by adding an appropriate perturbation. From the viewpoint of reaction control, continuous emulsion polymerization of vinyl acetate was conducted. It has been found that particle size distribution of latex particles oscillates with a very large time period owing to the effect of coupling reaction, mixing and particle aggregation dynamics. This research project successfully developed a stochastic model which considers the competitive interaction between polymerization reaction and aggregation of latex particles. Less