Magnetic Resonance Velocimetry of Particle Hydrodynamics in a Three-Dimensional Draft Tube Spout-Fluid Bed
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2024
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Other Conference Item
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Abstract
Draft tube spout-fluid beds (DTSFB) are widely used industrial reactors for processes requiring intensive mixing of solids and high heat and mass transfer rates between contacting gas and solid phases, such as particle drying1 and coating2. Due to the presence of a draft tube, the solid flow in a DTSFB is compartmentalized in a slow annular region and a fast spout in the draft tube, whereby the gap height of the draft tube regulates the particle circulation rate and the gas contacting time3. However, the inherent opacity of granular materials impedes the visual examination of the complex, internal hydrodynamics found in DTSFBs. Hence, semicircular beds4 or visual probes5 are often used to inspect the dynamics, which, in turn, perturb the particle flow due to the presence of additional walls or the insertion of probes. The present work employs magnetic resonance imaging (MRI) to non-invasively study the hydrodynamics of the solid phase in a fully three-dimensional DTSFB6. To this end, a lab-scale spout-fluid bed of oil-filled particles is equipped with a draft tube and measured by a 16-channel radio-frequency detector array in a 3T MRI scanner7,8. Solid distribution maps and particle velocity maps are obtained for various operational settings of the DTSFB, allowing to assess the entrainment of solid material from the annular region to the draft tube and, additionally, revealing flow phenomena such as a vena contracta flow at the entrance of the draft tube and the suppression of gas bubbling in the annular region of the bed. Complementary simulations using the discrete element method coupled with computational fluid dynamics confirm the experimental observations and provide further insight into the gas flow field of the DTSFB which is currently inaccessible by magnetic resonance imaging.
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published
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2024 AIChE Annual Meeting Proceedings
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American Institute of Chemical Engineers
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AIChE Annual Meeting 2024
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03865 - Müller, Christoph R. / Müller, Christoph R.
09548 - Kozerke, Sebastian / Kozerke, Sebastian
03628 - Prüssmann, Klaas P. / Prüssmann, Klaas P.
Notes
Conference lecture held on October 28, 2024
Funding
182692 - Understanding multi-phase particulate systems: from (reactive) gas-fluidized beds to dense suspensions via advanced magnetic resonance imaging (MRI) and Lagrangian modeling (SNF)
180544 - NCCR Catalysis (phase I) (SNF)
180544 - NCCR Catalysis (phase I) (SNF)
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