Solids Circulation in Spouted and Spout-Fluid Beds With Draft-Tubes

Muir, James R.; Berruti, Franco; Behie, Leo A.

doi:10.1080/00986449008940553

Cited by 66 publications

(64 citation statements)

References 14 publications

(11 reference statements)

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“…One observes periodic pulsations of bed-flow at frequencies ranging from 4 to 12 Hz. This phenomenon was observed by Muir et al (1990), who found that for their apparatus configuration the flow of particles occurred at frequencies ranging from 8 to 12 Hz (increasing with increasing gas flow) over the range of flows studied. Moreover, they observed that the solids crossed into the jet and covered the inlet.…”

supporting

confidence: 53%

Periodic Fluctuations of Flow and Porosity in Spouted Beds

Szafran

Kmieć

2006

Transp Porous Med

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The results of experimental investigations of bed flow hydrodynamics in spouted beds are compared with CFD simulations (Eulerian-Eulerian approach) for two different column geometries. The experimental results of bed porosity and fluctuation frequency of mass flow rate of grain in the fountain region are compared with the corresponding results of simulations. The simulation results confirmed the observations of Muir et al. (1990, Chem. Eng. Comm. 88: 153-171) and Yang and Keairns (1978, AlchE Symp. Ser. No. 176 74: 218) that fluctuations of bed flow in DTSB are caused by particle cluster formation in the loading region at the bottom of column.The solids cross into the jet and cover the column inlet and are carried upward periodically through a draft tube. Subsequent figures obtained from simulations, which show stages of particle cluster formation at the entrance of column, exactly match visual observations. The frequency of fluctuations of grain mass flow rate predicted in simulations (∼5-6 Hz) is in the range of that experimentally determined. The fluctuating inflow of solids results in slug formation and explains the vertical variations of height and porosity of the fountain. NotationGravity acceleration (m/s 2 ) h bed Initial height of bed (m) = I Identity tensor

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supporting

confidence: 53%

Periodic Fluctuations of Flow and Porosity in Spouted Beds

Szafran

Kmieć

2006

Transp Porous Med

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“…At the same time, a continuous percolation of gas from the spout region to the annular region exists. If the operational bed height is larger than the maximum spoutable bed depth H m , the spout cannot support the bed, and a transition from spout to collapse occurs [2][3]. In addition, it is also reported that the elevated temperature causes a decrease in H m and the stable spout eventually disappears at temperatures above 420°C despite the changing operating variables [4].…”

Section: Introductionmentioning

confidence: 99%

“…Those existing studies mainly focused on the dependence of solid circulation rate on operating variables such as draft tube diameter, particle size, length of entrainment region, gas velocity, etc. [22][23][24][25][26][27]. It is also impossible to extend empirical correlations and theoretical analyses developed from the experiments of conventional systems to the applications of DTSBs.…”

Section: Introductionmentioning

confidence: 99%

Effects of Draft Tubes on Particle Velocity Profiles in Spouted Beds

Zhao

Yao

2006

Chem Eng & Technol

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The vertical particle velocity profiles in a full-column cylindrical conical spouted bed, with or without a draft tube, are measured using a fibre optic probe system. The profiles have different characteristics for a draft tube spouted bed (DTSB) than for a conventional spouted bed (CSB). The spout of a CSB consists of a central flow where particle velocities fit exponential distributions, and a boundary layer where particle velocities are nearly uniform. The spout of a DTSB has no boundary layer and its radial particle velocity profiles are approximately linear. The particle velocities in the spout of a DTSB increase when superficial gas velocity increases, draft tube diameter decreases, or when entrainment height decreases. A kinematic model has been used to simulate the granular flow in the annulus of a CSB and DTSB, and they are compared with the experiments. The particle velocities in the annulus of a DTSB are much lower than that of a CSB. Their radial profiles are also different with a CSB. The dependence of particle velocities in the annulus of a DTSB on superficial gas velocity, draft tube diameter, and entrainment height are also discussed. One concludes that the draft tube diameter and entrainment height are two key factors for the solid circulation rate of a DTSB.

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“…Previous work (e.g. Muir et al, 1990) has shown that spouting can be enhanced by the insertion of an impermeable draft tube. Experiments were therefore carried out on dry spouting of the 6 mm polystyrene spheres using the draft tube set-up described above.…”

Section: Enhancement Measurementsmentioning

confidence: 99%

Spouting Enhancement by Addition of Small Quantities of Liquid to Gas-Spouted Beds

et al. 2008

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L'ajout d'eau liquide à des lits de particules de polystyrène de plus de 3 mm de diamètre améliore le jaillissement en causant une diminution de la vitesse de jaillissement minimale. Alors que le degré d'amélioration est du point de vue quantitatif comparable à ce que nous avons indiqué antérieurement pour des lits fl uidisés à larges particules hydrophobes légères, le mécanisme est différent. L'amélioration du jaillissement se produit parce que le liquide s'agglomère à l'interface jet-espace annulaire, formant un tube d'aspiration quasi imperméable effi cace, ce qui a pour effet d'accroître la vitesse du gaz en haut du jet.

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Solids Circulation in Spouted and Spout-Fluid Beds With Draft-Tubes

Abstract: Muir, J. R. (1988). Solids circulation in spouted and spout-fluid beds with draft-tubes (Unpublished master's thesis).

Cited by 66 publications

References 14 publications

Periodic Fluctuations of Flow and Porosity in Spouted Beds

Periodic Fluctuations of Flow and Porosity in Spouted Beds

Effects of Draft Tubes on Particle Velocity Profiles in Spouted Beds

Spouting Enhancement by Addition of Small Quantities of Liquid to Gas-Spouted Beds

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