Fluidization of nanoparticle agglomerates assisted by combining vibration and stirring methods

Zhao, Zhiduan; Liu, Daoyin; Ma, Jiliang; Chen, Xiaoping

doi:10.1016/j.cej.2020.124213

Cited by 47 publications

(19 citation statements)

References 61 publications

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“…Mixing with inert particles of appropriate physical properties has also been reported as a strategy to enhance the fluidization hydrodynamics of difficult-to-fluidize particles [30][31][32][33]. In some cases, a combination of two different assisted fluidization techniques has been utilized to improve the fluidization quality and suppress the size segregation of the bed material along the height [20,[34][35][36].…”

Section: Introductionmentioning

confidence: 99%

Pulsed Fluidization of Nanosilica: Rigorous Evaluation of the Efficacy of Pulsation Frequency

2022

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Assisted fluidization techniques can significantly improve the hydrodynamics of difficult- to-fluidize solids. Among these techniques, the pulsed flow strategy is highly promising owing to its cost-effectiveness and amenability to implementation for largescale processing. Using commercial-grade, highly porous nanosilica that shows strong agglomeration behavior, we implemented the pulsed flow with square-wave pulsation schemes of 0.05, 0.10, and 0.25 Hz frequencies, and compared their effectiveness in each case. Besides the conventional approach of assessing their efficacy using the pressure drop data, we have proposed a new approach in this work that consists of computing the power of the overall pressure drop transient signals. Using the theoretical value, i.e., the effective bed weight per unit area as a reference, the percentage increase in the power was 27 ± 4, 71 ± 5, and 128 ± 4, respectively, for 0.05, 0.10, and 0.25 Hz pulsation frequencies. In fact, the average pressure drop values were substantially higher when the partial bed collapse occurred between successive pulsations when compared with the case of low-frequency pulsations. The pulsation frequency also affected the evolution of local bed dynamics in various bed regions during the expansion and collapse of the bed. Moreover, the local and global pressure transients have shown interesting mutual correlations which were otherwise not evident from their individual transient profiles.

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Section: Introductionmentioning

confidence: 99%

Pulsed Fluidization of Nanosilica: Rigorous Evaluation of the Efficacy of Pulsation Frequency

2022

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“…These agglomerates are sometimes several thousand times larger than the primary size of the particles. [ 6–9 ] This phenomenon inevitably causes a loss of the valuable surface area, thereby often compromising the efficacy of the fluidized bed technology in processing ultrafine powders.…”

Section: Introductionmentioning

confidence: 99%

“…These techniques mainly employ strategies to mitigate the effect of IPFs. [ 6,10–25 ] For example, mechanical vibrations have been utilized to improve the fluidization behaviour and suppress segregation phenomenon along the bed height, [ 20,25 ] leading to better quality products. [ 26 ] Barletta et al [ 21 ] studied the effect of frequency and acceleration on the fluidization behaviour of FCC powder by monitoring the pressure drop and the bed height.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of partially collapsing pulsed fluidized bed

2021

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The use of flow pulsation as an effective assisted fluidization technique has been suggested in a number of applications, such as drying of food and pharmaceutical products, dry beneficiation of coal, and deagglomeration of nanopowders, owing mainly to its cost‐effectiveness and ease of implementation. The efficacy of this technique is, however, greatly affected by the frequency of pulsation since it controls the collapse dynamics of the fluidized bed. In this study, using ultrafine hydrophilic nanosilica with strong agglomeration tendencies, the pulsation frequency was controlled to allow only partial collapse of the bed between two successive pulsations while the global and local dynamics in different bed regions were carefully monitored. Besides the usual advantages associated with assisted fluidization techniques, such as lower minimum fluidization velocity, higher bed expansion, and elimination of bed non‐homogeneities, the continuous and intense solid motion imparted by the partial bed collapse caused a more substantial increase in the overall pressure drop than the one obtained with the conventional unassisted fluidization. The results of the frequency domain analysis highlighted the fact that the effect of pulsation event was felt differently in different regions of the bed depending upon the amplitude of the pulsation. These results were further corroborated by the similarity analysis.

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“…Common assisted fluidization techniques are based on the use of acoustics [4][5][6][7][8], particle-mixing [9][10][11][12][13][14][15], flow pulsations [16][17][18][19][20][21][22][23][24][25][26], and mechanical vibrations [27][28][29][30][31][32][33]. The combination of two of assisted fluidization techniques has also been suggested in some cases [15,[34][35][36].…”

Section: Introductionmentioning

confidence: 99%

“…Stirring using an impeller in the bottom of the bed somehow helped to mitigate this axial agglomerate size non-uniformity. However, the combination of assisted-fluidization techniques of vibration and stirring failed to completely eliminate the size segregation of agglomerates [36]. Therefore, the pulsed bed dynamics is carefully monitored in the upper, central, and lower regions of the fluidized bed using several sensitive pressure transducers located along the height of the fluidized bed to delineate the local fluidization behavior.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics of Pulsed Fluidized Bed of Ultrafine Powder: Fully Collapsing Fluidized Bed

et al. 2020

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The processing of fine and ultrafine particles using a fluidized bed is challenging in view of their unpredictable hydrodynamic behavior due to interparticle forces. The use of assisted fluidization techniques in such cases can be effective in improving the bed hydrodynamics. This work investigates the dynamics of pulsed fluidized bed of ultrafine nanosilica subjected to square-wave flow pulsations. The pulse duration used in this study is sufficient to allow the complete collapse of the pulsed fluidized bed between two consecutive flow pulsations. The proposed pulsation strategy is carefully implemented using electronic mass flow controllers with the help of analog output signals from data acquisition system. Given that the different regions of the fluidized bed exhibit varying dynamics, which together contribute to overall bed dynamics, the bed transients in the upper, central, and lower regions of the fluidized bed are monitored using several sensitive pressure transducers located along the height of the bed. The effect of the flow pulsation on the hydrodynamics of the fluidized bed is rigorously characterized. A significant reduction in the minimum fluidization velocity was obtained and an increase in the bed homogeneity was observed due to flow pulsations. The frequency domain analysis of the signals clearly delineated the frequency of the various events occurring during the fluidization.

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Fluidization of nanoparticle agglomerates assisted by combining vibration and stirring methods

Cited by 47 publications

References 61 publications

Pulsed Fluidization of Nanosilica: Rigorous Evaluation of the Efficacy of Pulsation Frequency

Pulsed Fluidization of Nanosilica: Rigorous Evaluation of the Efficacy of Pulsation Frequency

Dynamics of partially collapsing pulsed fluidized bed

Hydrodynamics of Pulsed Fluidized Bed of Ultrafine Powder: Fully Collapsing Fluidized Bed

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