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Dense upflow fluidized bed (DUFB) solar receivers of high aspect ratio: Different fluidization modes through inserting bubble rupture promoters

Deng, Yimin and Sabatier, Florian and Dewil, Raf and Flamant, Gilles and Le Gal, Alex and Gueguen, Ronny and Baeyens, Jan and Shuo, Li and Ansart, Renaud Dense upflow fluidized bed (DUFB) solar receivers of high aspect ratio: Different fluidization modes through inserting bubble rupture promoters. ( In Press: 2021) Chemical Engineering Journal, 418. 129376. ISSN 1385-8947

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Official URL: https://doi.org/10.1016/j.cej.2021.129376

Abstract

A fluidized bed of Geldart-A particles is promoted as heat transfer fluid in the tubular solar receivers of solar towers. A pressure-driven upward particle flow affects the hydrodynamic flow structure and properties of the fluidized bed. Experiments involved a tube of 0.05 m internal diameter but of very high height/diameter ratio (>120), representative of the future solar receiver and of numerous chemical reactors. Solid circulation fluxes and aeration velocities were varied. Configurations of a bare tube and a tube with bubble rupture promoters were compared. In the bare tube, freely bubbling is transformed into axi-symmetric slugging at a bed level of ~1 m. With bubble rupture promoters, freely bubbling prevails to about a bed level of 3 m, and a turbulent fluidization mode develops higher up the tube (a more chaotic two-phase system with elongated and unstable “gas voids” and “dense solid clusters”), without axi-symmetric slugging detected. Experimental results for both tube configurations were assessed and compared with CFD predictions by the Euler n-fluid code, NEPTUNE_CFD. A good agreement of bed properties was obtained for slug/void frequencies and solids volume fraction in both tube configurations. BRPs moreover enhance the bubble through flow of the fluidizing gas, thus limiting the visible bubble flow rate and bubble sizes while increasing the gas/particle contact, and hence important in designing multi-tube chemical reactors. Whereas slugging limits the heat transfer from the tube wall to the suspension at ~200 W/m2K, the presence of BRPs maintains a heat transfer coefficient in excess of 600 W/m2K.

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Beijing University of Chemical Technology - BUCT (CHINA)
Other partners > Katholieke Universiteit Leuven - KU LEUVEN (BELGIUM)
Other partners > Université de Perpignan Via Domitia - UPVD (FRANCE)
Laboratory name:
Funders:
European Commission
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Deposited On:26 Apr 2021 10:06

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