Bubble size reduction in electric-field-enhanced fluidized beds

Willigen, F. Kleijn van; Ommen, J. Ruud van; Turnhout, J. van; Bleek, C.M. van den

doi:10.1016/j.elstat.2005.03.065

Cited by 28 publications

(13 citation statements)

References 3 publications

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“…It was found that the fluctuation of bed level was significantly increased when the particles were not charged, and the average porosity of the bed was increased by 6% compared with the saturated charged particles, indicating that electrostatic effect made the bubble volume fraction reduce (Dong et al, 2015a). This phenomenon is in accordance with the external electric field on bubbles, which would make diameters of a single bubble and bubble diameters in fluidized bed decrease and the number of bubbles reduce (Kleijn van Willigen et al, 2005;Sun et al, 2015).…”

Section: Fig4 Average Bubble Diameters Along With the Bed Height Within 10 Ssupporting

confidence: 57%

Critical comparison of electrostatic effects on hydrodynamics and heat transfer in a bubbling fluidized bed with a central jet

Wang

Hernández-Jiménez

Lungu

et al. 2018

Chemical Engineering Science

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In many industrial process, electrostatic charges are inevitable. and affect the hydrodynamic behavior and heat transfer ability of chemical equipment. A comprehensive study of the electrostatic effect on bubble behavior, particle fluctuation velocity and heat transfer coefficient in the fluidized bed with a central jet has been evaluated in this paper by Eulerian-Eulerian two fluid model coupled with electrostatic model and energy model. The simulated voidage profiles at different positions, bubble detachment time and initial bubble diameter are compared with experiment results from the literature. The bubble behaviors including bubble frequency and bubble numbers, combined with particle fluctuation parameters are analyzed in both charged and uncharged system. Electrostatic effect on two kinds of heat transfer coefficients are quantitatively compared, namely bubble to emulsion phase heat transfers based on the gas throughflow velocity and gas solid local heat transfer. Simulation results show that electrostatic charges decrease bubble numbers and granular temperature, whereas the averaged heat transfer coefficients are enhanced. Overall, the electrostatic effect on the hydrodynamic and heat transfer characteristics can be revealed.

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Section: Fig4 Average Bubble Diameters Along With the Bed Height Within 10 Ssupporting

confidence: 57%

Critical comparison of electrostatic effects on hydrodynamics and heat transfer in a bubbling fluidized bed with a central jet

Wang

Hernández-Jiménez

Lungu

et al. 2018

Chemical Engineering Science

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show abstract

“…After reviewing the influences of different electric fields on the fluidized bed hydrodynamics, van Willigen proposed that the low frequency AC fields with strengths of 2-5 kV/cm were optimal for decreasing bubble number in the bed, while the DC fields had more effects but often led to spouting, stringing and cohesion of particles [20]. He then measured the external electric field influences on the bubble size in the fluidized bed by pressure fluctuation method, and proposed the optimized external electric field parameters [5,21]. The bubble size can be efficiently reduced by the external electric field with frequency of 5-20 Hz for smaller particles (77 lm), and with frequency of 20-70 Hz for larger particles (700 lm).…”

Section: Introductionmentioning

confidence: 99%

Effects of external electric field on bubble and charged particle hydrodynamics in a gas–solid fluidized bed

Sun

Yang

Zhu

2015

Advanced Powder Technology

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“…Generally, it is observed that the field promotes the formation of strings of polarized particles that tend to follow the field lines and fill in the bubbles, thus impeding their growth. Theoretical and experimental studies8–10 have demonstrated that electric fields of the order of 1 kV/cm are effective in changing the behavior from Geldart B to Geldart A stable fluidization. Semi‐insulating grains are required for charge relaxation times to be comparable to the typical time between grain collisions, which allows for charge exchange during collisions, thus preventing the grains from charge accumulation.…”

Section: Introductionmentioning

confidence: 99%

“…Semi‐insulating grains are required for charge relaxation times to be comparable to the typical time between grain collisions, which allows for charge exchange during collisions, thus preventing the grains from charge accumulation. Furthermore, the increase of surface conductivity allows for higher polarizability of the particles,10 which enhances interparticle attraction. Surface conductivity is usually enhanced in practice by fluidizing the grains with humidified air 9.…”

Section: Introductionmentioning

confidence: 99%

Enhanced nanofluidization by alternating electric fields

et al. 2009

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We show experimental results on a proposed technique to enhance the fluidization of nanoparticle beds. This technique consists of the application of an alternating electric field to the nanofluidized bed. Three different field configurations have been tested: co-flow field, cross-flow field, and variable field configurations. Nanoparticle agglomerates are naturally charged by contact and tribo charging mechanisms and therefore are agitated by the action of the externally applied field, which enhance fluidization. According to our observations, the best results are obtained for the variable field configuration. In this configuration, the electric field strength is higher at the bottom of the bed, whereas it is almost negligible at the free surface. Thus, the larger agglomerates, which tend to sink at the bottom of the bed due to stratification, and usually impede uniform fluidization, are strongly agitated. It is thought that the strong agitation of the bigger agglomerates that usually sink to the bottom of the bed contributes to further homogenize the distribution of the gas flow within the bed by destabilizing the development of gas channels close to the gas distributor. On the other hand, the smaller agglomerates at the vicinity of the free surface are just weakly excited. Consequently, fluidization is greatly enhanced, whereas at the same time excessive elutriation is avoided. It is demonstrated that this technique is even suitable to achieve highly expanded fluidization of unsieved nanopowder samples even though the fluidization state returns to be heterogeneous upon the electric field being turned off. V V C 2009 American Institute of Chemical Engineers AIChE J, 56: 54-65, 2010

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Bubble size reduction in electric-field-enhanced fluidized beds

Cited by 28 publications

References 3 publications

Critical comparison of electrostatic effects on hydrodynamics and heat transfer in a bubbling fluidized bed with a central jet

Critical comparison of electrostatic effects on hydrodynamics and heat transfer in a bubbling fluidized bed with a central jet

Effects of external electric field on bubble and charged particle hydrodynamics in a gas–solid fluidized bed

Enhanced nanofluidization by alternating electric fields

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