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Magnetic resonance imaging of gas dynamics in the freeboard of fixed beds and bubbling fluidized beds

Accepted version
Peer-reviewed

Repository DOI


Type

Article

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Authors

Boyce, CM 
Rice, NP 
Davidson, JF 
Sederman, AJ 
Dennis, JS 

Abstract

Magnetic resonance imaging (MRI) was used to measure directly gas velocity and gas velocity distribution in the freeboard region of a fluidized bed (52 mm dia.) under bubbling fluidization and just below minimum fluidization. The bed consisted of poppy seed particles 1.1 mm in diameter and was fluidized using SF6 gas at 7.5 barg for MRI purposes. In the system, bubbles approximately 20 mm in diameter rose through the centre of the bed. In the case of bubbling fluidization, time-averaged velocity maps at different vertical positions in the freeboard showed downward moving gas in the centre of the bed and upward moving gas near the walls for this particular bed. However, below minimum fluidization conditions, the profiles of gas velocity in the freeboard were flat, with respect to the radial dimension, with minor and random spatial variance, indicating that the profiles observed during bubbling arose from bubble breakthrough. The reasons for these observed patterns of flow are discussed.

Description

Keywords

Fluidized beds, Freeboard, Magnetic resonance imaging, Flow measurement

Journal Title

Chemical Engineering Science

Conference Name

Journal ISSN

0009-2509
1873-4405

Volume Title

Publisher

Elsevier BV
Sponsorship
CMB acknowledges the Gates Cambridge Trust for funding his research.