Investigation of Continuous-Flow Mixing of Non-Newtonian Fluids with Energy-Efficient Coaxial Mixers through Advanced Flow Visualization Techniques and Computational Fluid Dynamics

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Continuous-flow mixing is widely utilized in pharmaceutical, cosmetic, food, polymer, wastewater treatment, chemical, and biochemical industries since it has several advantages over the batch mixing operation. For instance, it provides high production rates, improves process control, and saves operation time and labor costs by eliminating loading and unloading materials and between-cycle cleaning. However, a comprehensive study performed in our research lab demonstrates that the continuous mixing of non-Newtonian fluids with the traditional mixers is far from ideal mixing and creates non-ideal flows (e.g. channeling, recirculation, and dead zone) that significantly affect the quality of the final product. The elimination of these non-ideal flows is a difficult task and requires a considerable increase in power consumption of the traditional mixers. Our preliminary study shows that the use of the coaxial mixers (a combination of a close clearance impeller and a central impeller) is a promising approach for the mixing of non-Newtonian fluids with complex rheology in the continuous mode. Thus, there is a clear need to fully investigate the use of energy-efficient coaxial mixers in the continuous-flow mixing of non-Newtonian fluids. The long term research program goal is to develop methodology and tools to design energy-efficient mixing systems for fluids with complex rheology in the continuous mode and to incorporate process dynamics into the scale up criteria through advanced flow visualization techniques and computational fluid dynamics. The work is of great importance to the chemical industry of Canada. Failure to provide the necessary mixing may result in severe manufacturing problems ranging from costly corrections in the plant to complete failure of a process. The annual loss due to poor mixing is estimated at $10 billion in the North America chemical industry alone [Handbook of Industrial Mixing]. The proposed research program will improve our understanding of continuous-flow mixing of complex fluids with the energy-efficient mixers and answer some of the fundamental questions about the design criteria. Applying the findings of this study will reduce the effect of non-ideal flows and improve variability reduction in the continuous mixing processes. This will lead to capital cost savings, chemical cost reduction, improved equipment design and selection, more reliable process monitoring and control, increased throughput for existing plant, improved quality of products, and more efficient use of power. Thus, the proposed research will contribute to the increased economic activity of the Canadian chemical industry, and will impact our society, quality of life, health and environment. It will also contribute to the education and training of HQP in the field of mixing technology, rheology, advanced flow visualization techniques (e.g. tomography and ultrasonic velocimetry), computational fluid dynamics, dynamic modeling and identification.