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Project

Design and Optimization of a Swirling Flow Reactor for Solid-Liquid Mixing

This dissertation provides an in-depth exploration of the Swirling Flow Reactor (SFR), a promising technology for solid-liquid mixing. Solid-liquid mixing is often applied in the chemical industry to keep solids in suspension for, amongst others, crystallization, adsorption, heterogeneous catalysis, etc. The most widely used technology to obtain a good degree of mixing is the mechanically stirred tank reactor. However, this technology is limited to small reactor volumes in case of high pressure/temperature processes due to sealing issues. The SFR is based on the principles of a Coanda jet and central particle circulation. The research, conducted through Computational Fluid Dynamics simulations, delves into various aspects of the SFR design, operation, and performance. This abstract encapsulates the key findings of the thesis and outlines future research directions.

The research initially delved into the design and operational mechanisms of the SFR, emphasizing the role of the Coanda jet and particle circulation in enhancing solid-liquid mixing. Through simulations using the Eulerian-Eulerian multiphase model and a realizable k-e turbulence model, the profound impact of specific geometrical parameters on the reactor's performance was revealed. The formation of a steady Coanda jet, the absence of massive sedimentation of particles and axial particle circulation were identified as key indicators of successful SFR operation. The study also confirmed the necessity of an annular filter/outlet design for facilitating Coanda jet formation and promoting downward flow in the vessel's centre. The research provides valuable insights into SFR design and operation, guiding future design and optimization efforts.

Using the previous findings, a specific configuration was selected for an in-depth analysis based on design parameters critical for optimal solid-liquid mixing and the facility to perform experiments. The chosen SFR, characterized by a Reynolds number Re = 130.000 and swirl number Sw*=1.7, demonstrated satisfactory mixing performance by achieving a homogeneity of H=0.945. The operation of the SFR was characterized by the formation of a Coanda jet flow (CoJF), which evolved into a spiralling upward flow along the reactor wall. The study also identified the significant role of the Precessing Vortex Core (PVC) in generating strong fluctuations and facilitating rapid particle dispersion.

Building further upon these novel insights, the research proposed an enhanced SFR design incorporating a draft tube. The improved SFR demonstrated superior mixing performance, achieving a homogeneity of 0.991. The additional draft tube successfully separated the inner and outer flows, improving particle distribution and reducing average velocity fluctuations within the vessel. Despite this, the draft tube guided most particles back to the nozzle, where significant velocity fluctuations and turbulence facilitated intense solid-liquid mixing. The research highlighted the role of the additional draft tube and the PVC in this enhanced mixing.

This pioneering research on the SFR advances the understanding of its design, operation, and mixing performance. While the research is still in its early stages, it underscores the SFR's potential as an effective solid-liquid mixing technology for a wide range of applications. The insights garnered from this research serve as a valuable resource for further SFR development, optimization, and industrial application. However, the future of the SFR hinges on continuous improvement, industrial validation, and a deeper understanding of operational conditions and design considerations.

Date:25 Sep 2019 →  19 Sep 2023
Keywords:loop reactor, swirling flow, computational fluid dynamics (CFD), vortex breakdown
Disciplines:Fluid mechanics and fluid dynamics
Project type:PhD project