Flow properties in the entrance and exit regions of a high-flux circulating fluidized bed riser

Yan, Aijie; Pärssinen, Janne; Zhu, Jesse

doi:10.1016/s0032-5910(02)00348-0

Cited by 25 publications

(14 citation statements)

References 8 publications

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“…Higher flow resistance as well as slip velocities are reported for abrupt exits . The solids distribution is found to vary significantly with solids flux . Depending on the particle terminal velocities, the riser and outlet geometries, the recirculation caused by a strongly restrictive outlet may extend throughout the riser, particularly for risers with a height to diameter ratio below 5 .…”

Section: Introductionmentioning

confidence: 92%

“…This is related to the high particle Stokes number (or high inertia) which allows for more diffused particle trajectories rather than particles following the fluid streamlines. Most experimental work in riser outlet sections focuses on measurements of pressure drop, solids distributions and solids fluxes . Studies reporting solids velocities are limited and mostly reveal either one or two coincident components of the solids velocities or the overall velocity magnitude .…”

Section: Introductionmentioning

confidence: 99%

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Three‐component solids velocity measurements in the outlet section of a riser

et al. 2016

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in Wiley Online Library (wileyonlinelibrary.com) Coincident (simultaneous) three-component particle velocity measurements performed using two laser Doppler anemometry probes at the outlet section of a 9 m high cylindrical riser are for the first time presented for dilute flow conditions. Near the blinded extension of the T-outlet a solids vortex is formed. Particle downflow along the riser wall opposite the outlet tube is observed, which is restricted to higher riser heights at higher gas flow rates. Increased velocity fluctuations are observed in the solids vortex and downflow region as well as at heights corresponding to the outlet tube. Contrary to the rest of the riser, in the downflow region time and ensemble velocity averages are not equal. Given the local bending of the streamlines, axial momentum transforms to radial and azimuthal momentum giving rise to the corresponding shear stresses. Turbulence intensity values indicate the edges of the downflow region.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Three‐component solids velocity measurements in the outlet section of a riser

et al. 2016

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“…The lateral particle diffusion velocities estimated in Eqs. (13) and (14) account for the particle interaction between the core and the annulus regions. Thus, the voidage predicted is more realistic especially in the top region to account for the exit shapes based on the slip factors calculated for the given radius of curvature.…”

Section: Axial Voidage Profilesmentioning

confidence: 99%

“…Pugsley et al [8] reported that the axial profile of pressure gradient shifted to significantly higher values when the riser was equipped with an abrupt exit and is dependent upon the riser diameter and the particle characteristics. More recent hydrodynamic works based on the exit geometry effects include [9][10][11]1,2,12,13]. Except the last two, all the others have reported significant experimental data to observe the effect of the riser exit shape on particle concentration in the exit region as well as in the rest of the riser column.…”

Section: Introductionmentioning

confidence: 99%

Modeling of axial bed-to-wall heat transfer in a CFB combustor with abrupt riser exit geometry

Gnanapragasam

Reddy

2008

International Journal of Heat and Mass Transfer

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“…The gas distributor design can also greatly affect the hydrodynamics of gas-solid flow in the bottom region of the CFB riser [15,18]. In addition, since the bottom region serves as an initial gas-solid mixing section for the whole CFB riser and the high solids holdup and reactant concentration there lead to a significant portion of the reaction in CFB riser reactors [33][34][35], the flow structures in the bottom region are critical to the overall CFB risers.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Flow Structure in Circulating Fluidized Bed Risers with FCC and Sand Particles

Huang

Zhu

2008

Chem Eng & Technol

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The combined influences of particle properties and nozzle gas distributor design on the axial and radial flow structure in two 100 mm i.d., 15.1 m and 10.5 m long risers with FCC and sand particles were investigated by measuring the axial pressure gradient profiles, and the axial and radial profiles of solids concentration. The results show that the nozzle gas distributor design has significant effects on the axial and radial flow structure for the FCC and sand particles. At lower superficial gas velocity of less than 8.0 m/s, the upward gas-solid flow of the sand particles decelerates in various degrees with the disappearing of the nozzle gas distributor effect. The upward gas-solid flow of the FCC particles, however, occurs without noticeable deceleration within the range of this study. In the acceleration section, the radial distributions of the local solids concentration of the FCC particles are more uniform than those of sand particles under the same operating conditions; while in the fully developed zone, the sand particles have a more uniform radial distribution than the FCC particles. The gas-solid flow is first developed in the center region, and then extends towards the wall. The overall flow development in the riser mainly depends on the local gas-solid flow in the wall region.

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Flow properties in the entrance and exit regions of a high-flux circulating fluidized bed riser

Cited by 25 publications

References 8 publications

Three‐component solids velocity measurements in the outlet section of a riser

Three‐component solids velocity measurements in the outlet section of a riser

Modeling of axial bed-to-wall heat transfer in a CFB combustor with abrupt riser exit geometry

Comparative Study of Flow Structure in Circulating Fluidized Bed Risers with FCC and Sand Particles

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