TY  - JOUR
N1  - Copyright © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
TI  - An investigation on the mechanics of homogeneous expansion in gas-fluidized beds
EP  -  105
AV  - public
VL  - 127
SP  - 95 
Y1  - 2015/05/04/
JF  - CHEMICAL ENGINEERING SCIENCE
KW  - Fluidization
KW  -  Homogeneous bed expansion
KW  -  Cohesive powders
KW  -  Interparticle forces
KW  -  Enduring particle-partide contacts
A1  - Oke, O
A1  - Lettieri, P
A1  - Mazzei, L
ID  - discovery1464221
N2  - The Richardson and Zaki (1954, Sedimentation and fluidization. Trans. Inst. Chem. Eng. 32, pp. 35?53.) equation has been used extensively to investigate the expansion profiles of homogeneous gas-fluidized beds. The experimental value of the parameter n appearing in the equation indicates how significantly interparticle forces affect the expansion of these beds, revealing the relative importance of these forces with respect to the fluid dynamic ones. In this work, we modeled the stable expansion of gas-fluidized beds of different diameter, accounting for enduring contacts among particles and wall effects. We solved the model numerically to obtain the bed expansion profiles, back-calculating from them the values of the parameter n. For all the cases considered, we observed that the values of n are higher than those obtained by purely fluid dynamic correlations, such as those advanced by Richardson and Zaki, and Rowe (1987, A convenient empirical equation for estimation of the Richardson and Zaki exponent. Chem. Eng. Sci. 42, pp. 2795.). This effect was more pronounced in beds of smaller diameter. To validate our model, we carried out fluidization and defluidization experiments, analyzing the results by means of the Richardson and Zaki equation. We obtained a reasonable agreement between numerical and experimental findings; this suggests that enduring contacts among particles, which are manifestations of cohesiveness, affect homogeneous bed expansion. This effect is amplified by wall friction.
SN  - 0009-2509
UR  - http://dx.doi.org/10.1016/j.ces.2015.01.020
ER  -