Magnetic resonance studies of jets in a gas–solid fluidised bed--颗粒学报PARTICUOLOGY

Pore, M., Chandrasekera, T. C., Holland, D. J., Wang, A., Wang, F., Marashdeh, Q., Mantle, M. D., Sederman, A. J., Fan, L.-S., Gladden, L. F., & Dennis, J. S. (2012). Magnetic resonance studies of jets in a gas–solid fluidised bed. Particuology, 10(2), 161–169. https://doi.org/10.1016/j.partic.2011.10.005

Magnetic resonance studies of jets in a gas–solid fluidised bed

Meenal Pore^a, Thusara C. Chandrasekera ^a, Daniel J. Holland ^a, Aining Wang ^b, Fei Wang ^b, Qussai Marashdeh ^b, Michael D. Mantle ^a, Andrew J. Sederman ^a, Liang-Shih Fan ^b, Lynn F. Gladden ^a, John S. Dennis ^a *

a Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
b The William G. Lowrie Department of Chemical and Biomolecular Engineering, Ohio State University, Columbus, OH 43210, USA

10.1016/j.partic.2011.10.005

Volume 10, Issue 2, April 2012, Pages 161-169

Received 15 August 2011, Revised 13 October 2011, Accepted 21 October 2011, Available online 11 February 2012.

E-mail: jsd3@cam.ac.uk

Highlights

► The bubbling region and dead zones around multiple jets were identified by MRI.

► Below the minimum fluidisation flow rate longer central jets were observed.

► Above the minimum fluidisation there were interactions between the outer jets.

► Comparable images of a jet from MRI and ECVT were demonstrated.

Abstract

Magnetic resonance imaging (MRI) has been used to study the behaviour of jets at the distributor of a 50 mm diameter fluidised bed of 0.5 mm diameter poppy seeds. Two perforated-plate distributors were examined, containing either 10 or 14 holes, each 1 mm diameter. Ultra-fast MR imaging was able to show the transient nature of the upper parts of the jets, where discrete bubbles are formed. Imaging in 3D showed that the central jets were the longest for flow rates below minimum fluidisation. Above minimum fluidisation, the outer jets, nearest the wall of the fluidised bed, arched inward towards the central axis. In this latter case, interpretation of the time-averaged 3D image required the use of ultra-fast MR imaging to identify the approximate height above the distributor at which discrete bubbles were formed. The apparently continuous void extending along the central axis above this height in the time-averaged 3D image was thus identified, using ultra-fast MR imaging, as representing the averaged paths of released bubbles. Time-averaged MR velocity mapping was also used to identify dead zones of stationary particles resting on the distributor between the jets. The dead zones could be observed when the superficial velocity of the gas approached minimum fluidisation, but they were smaller than those observed at lower gas superficial velocity. Comparable images of a single jet through 1.2 mm diameter poppy seeds from MRI and electrical capacitance volume tomography (ECVT) are also demonstrated.

Graphical abstract

Keywords

Fluidised bed; MRI; ECVT; Jets; Distributor design

文章导读