Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor--颗粒学报PARTICUOLOGY

Jiang, X., Yang, N., & Yang, B. (2016). Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor. Particuology, 27, 95-101. https://doi.org/10.1016/j.partic.2015.05.011

Computational fluid dynamics simulation of hydrodynamics in the riser of an external loop airlift reactor

Xuedong Jiang ^{a b}, Ning Yang ^b *, Bolun Yang ^a *

a Department of Chemical Engineering, State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
b Center for Mesoscience and State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China

10.1016/j.partic.2015.05.011

Volume 27, August 2016, Pages 95-101

Received 28 February 2015, Revised 21 April 2015, Accepted 16 May 2015, Available online 21 November 2015, Version of Record 14 June 2016.

E-mail: nyang@home.ipe.ac.cn; blunyang@mail.xjtu.edu.cn

Highlights

• The performances of three drag models were evaluated in the CFD simulation of a riser.

• DBS-local drag model gave more reasonable distributions of gas holdup.

• The ratio of drag coefficient to bubble diameter is smaller in center and larger near wall.

• Liquid velocity distributions were not affected by the drag models.

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.

Graphical abstract

Keywords

Computational fluid dynamics; External loop airlift reactor; Drag model; Gas holdup; Multiscale; Mesoscale

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