Solids flow diagram of a CFB riser using Geldart B-type powders--颗粒学报PARTICUOLOGY

Mahmoudi, S., Chan, C. W., Brems, A., Seville, J., & Baeyens, J. (2012). Solids flow diagram of a CFB riser using Geldart B-type powders. Particuology, 10(1), 51–61. https://doi.org/10.1016/j.partic.2011.09.002

Solids flow diagram of a CFB riser using Geldart B-type powders

Shiva Mahmoudi ^a, Chian Wen Chan ^a, Anke Brems ^b, Jonathan Seville ^c, Jan Baeyens ^c *

a University of Warwick, School of Engineering, Coventry CV4 7AL, UK
b Katholieke Universiteit Leuven, Department of Chemical Engineering, 3001 Heverlee, Belgium
c University of Surrey, Faculty of Engineering and Physical Sciences, Guildford GU2 7XH, UK

10.1016/j.partic.2011.09.002

Volume 10, Issue 1, February 2012, Pages 51-61

Received 26 March 2011, Revised 24 June 2011, Accepted 22 September 2011, Available online 6 December 2011. Show less

E-mail: Baeyens.J@gmail.com

Highlights

Abstract

Riser operating modes are vital to designing a circulating fluidized bed (CFB) reactor for a required process of either a gas–solid or a gas–catalytic nature. Different operating modes provide different solids’ residence times and mixing behaviors, which define the reactions’ efficiency and yield. The literature demonstrates distinct operating modes resulting from observed differences in slip factors and the range of particle velocities and their associated residence time distribution. The present research uses positron emission particle tracking (PEPT) in a riser of B-type bed material to determine the different operating modes by measuring (i) particle velocities and residence time distribution, (ii) population densities of these particles in the cross-sectional area of the riser, and (iii) solids flow pattern at the bottom of the riser. Data treatment defines four distinct solids hold-up regimes in the riser and proposes a “phase diagram” depicting the existence of the different operating modes (dilute, dense, core-annulus and combined) as a function of the superficial gas velocity and solids circulation flux in the riser. The delineated regimes have good agreement with available literature data and known industrial operations. Comparison with literature data for risers using A-type powders is also fair. The diagram enables CFB designers to better delineate operating characteristics.

Graphical abstract

Keywords

Phase diagram; Dilute riser flow; Turbulent fluidized bottom bed; Core-annulus flow; Dense riser up-flow

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