Two-dimensional and three-dimensional computational studies of hydrodynamics in the transition from bubbling to circulating fluidised bed


Armstrong, Lindsay-Marie, Gu, Sai and Luo, Kai H. (2010) Two-dimensional and three-dimensional computational studies of hydrodynamics in the transition from bubbling to circulating fluidised bed. Chemical Engineering Journal, 160, (1), 239-248. (doi:10.1016/j.cej.2010.02.032).

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Description/Abstract

This paper applies two-fluid modelling (TFM) to a two dimensional and three dimensional circulating fluidised bed (CFB). An energy minimisation multiscale based drag model (EMMS) is compared with a classical drag model, namely the Gidaspow model in the light of experimental data from the CFB. The axial particle velocities and the radial volume fraction at different heights are considered. The specularity coefficient responsible for the tangential solid velocities at the walls is varied to study the effect on the downflow of particles at the wall. The work is further extended to explore the effects of velocity variation on the flow distribution showing the transition from a bubbling to a fast fluidising regime. Furthermore, the diameters of the bubbles observed within the bubbling regime are compared with the Davidson’s bubble diameter model for a range of particle diameters. Varying the specularity coefficient showed that a free slip boundary condition underpredicted the downflow of particles at the wall and to add slight roughness to the wall gave a closer representation. The predictions for the 2D and 3D CFB axial velocities were in good agreement with the experimental data but the 2D results slightly overpredicted the core velocity. The transition from a bubbling to a fast fluidising regime as expected occurred once the inlet velocity exceeded the terminal velocity. The equivalent bubble diameter from the simulations agreed well with the calculated bubble diameter from the model.

Item Type: Article
ISSNs: 1385-8947 (print)
Keywords: cfd, hydrodynamics, circulating fluidised bed, eulerian, emms
Subjects: T Technology > TP Chemical technology
T Technology > TA Engineering (General). Civil engineering (General)
Divisions: University Structure - Pre August 2011 > School of Engineering Sciences
ePrint ID: 73225
Date Deposited: 04 Mar 2010
Last Modified: 28 Mar 2014 15:24
Research Funder: EPSRC
Projects:
Collaborative Research in Energy with South Africa:Scale-up modelling to answer Pyrolysis Challenge
Funded by: EPSRC (EP/G034281/1)
Led by: Sai GU
1 November 2009 to 30 April 2013
Contact Email Address: S.Gu@soton.ac.uk
URI: http://eprints.soton.ac.uk/id/eprint/73225

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