Multi-scale fluidization of ultrafine powders in a fast-bed-riser/conical-dipleg CFB loop

Li, Hongzhong; Tong, Hao

doi:10.1016/j.ces.2004.01.041

Cited by 21 publications

(8 citation statements)

References 7 publications

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“…As an approximation, when the gas velocity is not high, we can neglect its contribution to G. An attempt to include a gas velocity term in the correlation, namely, G = BU

_{italicg}^{α1}

(ε s − ε s 0 ) α2 , was made, but no significant improvement in accuracy was obtained. Although the agglomerate sizes often decreased with increasing bed heights,26 Figure 2b indicates that the variation is not much. In addition, CNTs are highly conductive and can be used as an anti‐electrostatic material,27 which allows a reasonable assumption of excluding the effect of electrostatic charges.…”

Section: Experimental Methodsmentioning

confidence: 94%

Hydrodynamics and gas mixing in a carbon nanotube agglomerate fluidized bed

Zhang

et al. 2006

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).A typical nanoscale fiber material, carbon nanotubes (CNTs), was fluidized in a 280 mm inner diameter (ID) nano-agglomerate fluidized bed (NAFB). The solids distribution and gas mixing were measured by a self-developed conductance method and the hydrogen tracer technique. Typical nano-agglomerate fluidization characteristics, such as high bed expansion ratio and multi-staged agglomerate structure, were observed. Fluidization experiments over a wide gas velocity range showed that the CNT agglomerates have agglomerate-bubbling-fluidization (ABF) characteristics. Particulate fluidization can also be achieved in the range 0.017;0.038 m/s, showing they also have Geldart-A particle characteristics. A systematic comparison of the transition velocities, solids distributions, and gas mixing between the fluidizations of CNT agglomerates and Geldart-A particles was carried out. CNT NAFBs have more non-uniform solids concentration profiles near the wall, but more homogenous micro-flow structures than Geldart-A particles, which leads to good gas mixing. These unique hydrodynamics behaviors are attributed to the difference in the microstructure between the nanoagglomerates and ordinary particles.

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“…As an approximation, when the gas velocity is not high, we can neglect its contribution to G. An attempt to include a gas velocity term in the correlation, namely, G = BU

_{italicg}^{α1}

Section: Experimental Methodsmentioning

confidence: 94%

Hydrodynamics and gas mixing in a carbon nanotube agglomerate fluidized bed

Zhang

et al. 2006

AIChE Journal

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“…A large number of reporting has been done on various aspects of CFB, especially on the hydrodynamics of the fast-fluidized bed [1][2][3][4][5][6][7][8][9]. Each CFB system is unique in its character and marked by some stable operational features.…”

Section: Introductionmentioning

confidence: 99%

Axial voidage profiles and identification of flow regimes in the riser of a circulating fluidized bed

Das

Bandyopadhyay

Meikap

et al. 2008

Chemical Engineering Journal

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“…Consequently, the objective of the current paper is to focus on the fluidization of zirconia and aluminum nanoparticles to investigate their performance in a fluidized bed. Although the fluidization of nanoparticles happens in an agglomerate state (Chaouki et al, 1985;Morooka et al, 1988;Iwadate and Horio, 1998;Wang et al, 1998Wang et al, , 2006Li et al, 1999;Li, 1999, 2000;Lu and Li, 2000;Matsuda et al, 2001Matsuda et al, , 2004Jung and Gidaspow, 2002;Yao et al, 2002;Watano et al, 2003;Mawatari et al, 2003a,b;Li and Tong, 2004;Nam et al, 2004;Zhu et al, 2004Zhu et al, , 2005Hakim et al, 2005;Yu et al, 2005;Jiradilok et al, 2006;Guo et al, 2006aGuo et al, ,b, 2007Gundogdu et al, 2007;Liu et al, 2007;Quevedo et al, 2007), it is very important to understand if the fluidization of these particles would be carried out homogeneously in terms of solid and gas phase concentrations within the bed. Otherwise, the polymer encapsulation will not be uniformly applied on the surface of ultrafine particles.…”

mentioning

confidence: 99%

“…n the last two decades, the fluidization of nanoparticles has been one of the most important research interests in the area of nanoparticle handling and processing (Chaouki et al, 1985;Morooka et al, 1988;Iwadate and Horio, 1998;Wang et al, 1998Wang et al, , 2006Li et al, 1999;Li, 1999, 2000;Lu and Li, 2000;Matsuda et al, 2001Matsuda et al, , 2004Jung and Gidaspow, 2002;Yao et al, 2002;Watano et al, 2003;Mawatari et al, 2003a,b;Li and Tong, 2004;Nam et al, 2004;Zhu et al, 2004Zhu et al, , 2005Hakim et al, 2005;Yu et al, 2005;Jiradilok et al, 2006;Guo et al, 2006aGuo et al, ,b, 2007Gundogdu et al, 2007;Liu et al, 2007;Quevedo et al, 2007). Researchers have dealt with different aspects of nanoparticle fluidization, for example, the evaluation of agglomerate size via force and energy balance (Chaouki et al, 1985;Morooka et al, 1988;Iwadate and Horio, 1998;Li, 1999, 2000;Lu and Li, 2000;Mawatari et al, 2003a;Matsuda et al, 2004;Guo et al, 2007), hydrodynamic modelling of the phenomenon (Chaouki et al, 1985;Iwadate and Horio, 1998;Wang et al, 1998;Li et al, 1999;Jung and Gidaspow, 2002;…”

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confidence: 99%

An evaluation of the solid hold‐up distribution in a fluidized bed of nanoparticles using radioactive densitometry and fibre optics

2008

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An experimental study was conducted to assess the solid hold-up distribution in a fluidized bed of zirconia and aluminum nanoparticles. For this purpose, two different techniques, radioactive densitometry and fibre optic measurement, were used. The results showed that while the fluidization of these nanoparticles occurs in the agglomeration state, it performs homogeneously in terms of phase concentration. This matter is important especially when a polymerization reaction should take place uniformly on the surface of nanoparticles, where the monomer is the fluidizing gas. Both techniques presented uniform solid hold-up distribution over the cross-section, although the fibre optic method overestimated the overall solid concentration, which was obtained based on bed expansion results. The radioactive densitometry was, however, capable of properly predicting the phase concentration within the bed according to the bed expansion observation. Finally, the effect of bulk density on the fluidization of nanoparticles was discussed by comparing the fluidization of different types of particulate materials.On a mené uneétude expérimentale pourévaluer la distribution de rétention de solide dans un lit fluidisé de nano particules de zircon et d'aluminium.À cette fin, deux techniques différentes, la densimétrie radioactive et la mesure par fibres optiques, ontété utilisées. Les résultats montrent qu'alors que la fluidisation de ces nano particules survientà l'état d'agglomération, elle est relativement performante en termes de concentration de phase. Cet aspect est important, car une réaction de polymérisation devrait se produire uniformémentà la surface des nano particules, le monomèreétant le gaz fluidifiant. Les deux techniques ont mis enévidence une distribution de rétention de solide uniforme dans la section transversale, bien que la méthode par fibres optiques ait surestimé la concentration de solide globale, obtenueà partir des résultats d'expansion du lit. Cependant, la densimétrie radioactive est capable de prédire de manière correcte la concentration de phase dans le lit d'après l'observation de l'expansion de lit. Enfin, l'effet de la masse volumique apparente sur la fluidisation des nano particules est examiné en comparant la fluidisation de différents types de matériaux particulaires.

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Multi-scale fluidization of ultrafine powders in a fast-bed-riser/conical-dipleg CFB loop

Cited by 21 publications

References 7 publications

Hydrodynamics and gas mixing in a carbon nanotube agglomerate fluidized bed

Hydrodynamics and gas mixing in a carbon nanotube agglomerate fluidized bed

Axial voidage profiles and identification of flow regimes in the riser of a circulating fluidized bed

An evaluation of the solid hold‐up distribution in a fluidized bed of nanoparticles using radioactive densitometry and fibre optics

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