Investigation of Mixing in Multiphase (gas, solid, and liquid) flow through Experimental and Numerical (Computational Fluid Dynamic) Techniques.

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Mixing of common non-Newtonian fluids, such as ketchup or mascara, is an important and challenging element of production in many economic sectors, including the chemical, biochemical, food, polymer, pulp & paper, cosmetic, wastewater treatment, and pharmaceutical industries. Unpredictability in process operations, such as mixing, decreases the uniformity of the product, resulting in a decline in product quality, and the need to use excess chemicals for further processing. The annual loss due to poor mixing is estimated at $10 billion in North American chemical industries alone. Multiphase mixing—mixing of solid and liquid, liquid and gas, or solid, liquid and gas—is a common task in most chemical and related industries. In multiphase mixing, agitation is necessary for tasks such as creating homogeneous suspensions, or to increase the contact area between gas bubbles and liquid and promote effective mixing. Designing mixing systems for multiphase applications is thus of great interest to industry. The important parts of mixing equipment are the impellers, which are used in mixing systems to suspend particles and/or disperse gas in non-Newtonian fluids. One recommended mixing system uses a coaxial mixer, which combines a close clearance impeller and an open impeller. However, the fundamental science behind this mixing system design with application in multiphase flow is limited and often relies on trial and error, which is expensive and inefficient. This research program will develop a general methodology to design multiphase flow mixing systems for fluids with complex flow characteristics (rheology). The program will combine advanced flow visualization techniques (e.g. particle image velocimetry, optic probes, and tomography) and advanced computational fluid dynamics (CFD). The proposed experimental and modeling research will improve our understanding of mixing phenomena in multiphase flow with coaxial mixers and answer some of the fundamental questions about system design criteria. For example, it will investigate questions about the selection of mixer type, range of impeller speed, and rotation modes, and how they correspond to mixing effectiveness in agitation of multiphase flow with complex rheology. The outcome of this research program will contribute significantly to the Canadian chemical industry. Improved mixing systems can lead to capital cost savings, reduction in chemical cost and consumption, improved performance of equipment, more reliable process monitoring and control, increased throughput for existing plants, enhanced product quality, and increases in energy efficiency. This research will also contribute to the education and training of HQP in the field of mixing technology, computational fluid dynamics, advanced fluid visualization techniques, rheology, multiphase flow, coaxial mixers, and non-Newtonian fluids.