Experimental study of the nature of gas streaming in deep fluidized beds of Geldart A particles

Karimipour, Shayan; Pugsley, Todd

doi:10.1016/j.cej.2010.05.040

Cited by 10 publications

(4 citation statements)

References 22 publications

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“…1 Group A powders are easy to circulate around fluidized and pneumatic conveying loops. Gross circulation of the powders, similar to gulf streaming in liquids, 9 occurs as soon as bubbles are present, producing considerable particle mixing. At higher gas velocities, bubbles appear to split and recoalesce frequently, resulting in a maximum stable bubble size if the diameter of the bed is big enough to avoid slugging, 10 as discussed further in the following discussion.…”

Section: Introductionmentioning

confidence: 99%

Bubbling and Slugging of Geldart Group A Powders in Small Diameter Columns

Kong

Tan

Baeyens

et al. 2017

Ind. Eng. Chem. Res.

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Bubbling and slugging were investigated in a 0.05 m internal diameter bed of Geldart group A powders. The slugging characteristics were assessed in terms of the operating parameters. Neither bed height nor particle properties affect the excess gas velocities at the onset of slugging, as predicted by the Stewart criterion. Slugging characteristics (length and frequency) and fluidized bed properties were determined. The bottom zone of the bed is freely bubbling, and the bubble sizes can be predicted by d B = 0.047H 0.37, where d B is the frontal diameter of the bubble and H is the fluidized bed height. Mostly, wall slugs occur higher in the bed when d B exceeds about 50% of the column diameter. The slug frequency varies with the height in the bed but reaches an equilibrium value of 1 Hz for bed heights exceeding ∼1 m. Three distinct zones appear in a deep bed of group A powders. The design and scale-up should combine the bubbling and slugging modes within their corresponding regions in the bed.

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Section: Introductionmentioning

confidence: 99%

Bubbling and Slugging of Geldart Group A Powders in Small Diameter Columns

Kong

Tan

Baeyens

et al. 2017

Ind. Eng. Chem. Res.

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show abstract

“…Group A powders are easily circulated around fluidized and pneumatic conveying loops. Bubbles induce a gross circulation of the powders, similar to gulf streaming in liquids 5 , producing considerable particle mixing. At higher gas velocities, bubbles split and recoalesce frequently, resulting in a maximum stable bubble size if the diameter of the bed is large enough to avoid slugging 2 .…”

Section: Powder Properties and Common Conveying Systemsmentioning

confidence: 99%

Experiments support an improved model for particle transport in fluidized beds

Zhang

Kong

Tan

et al. 2017

Sci Rep

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The upwards flow of particles in an Upflow Bubbling Fluidized Bed (UBFB) is studied experimentally and modelled from pressure drop considerations and energy loss equations. For Geldart group A powders tested, the upward solid flux, G s, in the tube can be expressed in terms of the applied superficial gas velocity, the free fall (terminal) velocity of the particles during their hindered settling, KU t, the pressure exerted at the base of the conveyor tube, and the tube length. The model expression can be used for design purposes, with K, the correction factor for hindered settling of the particles, approximately equal to 0.1 at high G s-values, but a function of the solids fraction in the upward conveying. The energy efficiency of the system increases with increasing U and Gs. The model equation was tentatively applied to predict the effects of particle size, tube length and operation in Circulating Fluidized Bed mode. It is demonstrated that the UBFB is an efficient and flexible way of transporting particles upwards, with limited particle attrition or tube erosion due to the low gas velocity applied.

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“…In the field of gas-solid two phase flows, the fluctuation of pressure drops has previously been investigated by power spectral analysis [41,42] and wavelet transform [43,44] . Power spectral analysis describes the power contributed to the signal by a specific frequency, per unit frequency.…”

Section: Void Fractionmentioning

confidence: 99%