Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor |
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| Institution: | 1. Department of Chemical Engineering, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China;2. Center for Mesoscience and State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China;1. Department of Chemical Engineering, College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China;2. Suzhou Key Laboratory of Green Chemical Engineering, School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China;1. State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, P.O. Box 353, Beijing 100190, PR China;2. Wuhan 2nd Ship Design and Research Institute, Wuhan 430064, Hubei Province, PR China;1. Centre for Catalysis Research and Innovation, Department of Chemical and Biological Engineering, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5;2. Chemical and Biochemical Engineering Department, University of Western Ontario, London, Ontario, Canada N6A 5B9;3. Syncrude Canada Ltd., 9421-17 Avenue, Edmonton, Alberta, Canada T6N 1H4;1. Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang, 110819, China;2. School of Metallurgy, Northeastern University, Shenyang, 110819, China |
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| Abstract: | Local hydrodynamics in the riser of an external loop airlift reactor (EL-ALR) are identified and the performances of three drag models are evaluated in computational fluid dynamics simulation. The simulation results show that the Schiller–Naumann drag model underestimated the local gas holdup at lower superficial gas velocity whereas the Tomiyama drag model overestimated that at higher superficial gas velocity. By contrast, the dual-bubble-size (DBS)-local drag model gave more reasonable radial and axial distributions of gas holdup in all cases. The reason is that the DBS-local drag model gave correct values of the lumped parameter, i.e., the ratio of the drag coefficient to bubble diameter, for varying operating conditions and radial positions. This ratio is reasonably expected to decrease with increasing superficial gas velocity and be smaller in the center and larger near the wall. Only the DBS-local drag model correctly reproduced these trends. The radial profiles of the axial velocity of the liquid and gas predicted by the DBS-local model also agreed well with experimental data. |
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| Keywords: | Computational fluid dynamics External loop airlift reactor Drag model Gas holdup Multiscale Mesoscale |
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