Effects of the riser exit geometries on the hydrodynamics and solids back-mixing in CFB risers: 3D simulation using CPFD approach

Shi, Xiaogang; Wu, Yingya; Lan, Xingying; Liu, Feng; Gao, Jinsen

doi:10.1016/j.powtec.2015.06.049

Cited by 37 publications

(11 citation statements)

References 65 publications

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“…The gas inlet is in the bottom of the riser and the solids inlet is from the side feeding pipe. The effects of different exit structures such as type C, type T, and type L could also be studied by this method [13].…”

Section: Introductionmentioning

confidence: 99%

Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed

Wang

Shi

et al. 2019

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With the development of computing power, the simulation of circulating fluidized bed (CFB) has developed from riser-simplified simulation to riser-only simulation, then to full-loop simulation. This paper compared these three methods based on pilot-scale CFB experiment data to find the scope of application of each method. All these simulations, using the Eulerian–Eulerian two-fluid model with the kinetic theory of granular theory, were conducted to simulate a pilot-scale CFB. The hydrodynamics, such as pressure balance, solids holdup distribution, solids velocity distribution, and instantaneous mass flow rates in the riser or CFB system, were investigated in different simulations. By comparing the results from different methods, it was found that riser-simplified simulation is not sufficient to obtain accurate hydrodynamics, especially in higher solids circulating rates. The riser-only simulation is able to make a reasonable prediction of time-averaged behaviors of gas–solids in most parts of riser but the entrance region. Further, the full-loop simulation can not only predict precise results, but also obtain comprehensive details and instantaneous information in the CFB system.

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Section: Introductionmentioning

confidence: 99%

Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed

Wang

Shi

et al. 2019

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“…The MP-PIC method was implemented to the simulations of multiphase and thermal reacting flows in fluidized bed (Li et al, 2013;Berrouk et al, 2017;Xie et al, 2017). This approach has been utilized in several cold flow modeling studies including bubbling fluidized beds (Weber et al, 2013;Liang et al 2014;Fotovat et al, 2015), risers of CFB's (Chen et al, 2013;Shi et al, 2014;Shi et al, 2015a;Shi et al, 2015b;Wang et al, 2015) and full loop CFB systems (Wang et al, 2014;Tu and Wang, 2018).…”

Section: Introductionmentioning

confidence: 99%

Cold Flow Simulation of a 30 kWth CFB Riser with CPFD

Raheem

Yılmaz

Özdoĝan

2020

JAFM

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A 30 kWth Circulating fluidized bed (CFB) combustor is experimentally and numerically investigated under cold flow conditions. Barracuda software based on Computational Particle Fluid Dynamics (CPFD) method is utilized for simulations. The influences of bed inventory and drag model on flow hydrodynamics were investigated considering pressure and velocity profiles and particle concentration. Two advanced drag models, namely Energy minimization multi-scale (EMMS) and Wen-Yu/Ergun were selected for this study. The simulations were performed with initial bed material masses of 3.79, 4.55 and 5.20 kg corresponding to 2.5, 3 and 3.5 diameters height of riser, respectively. With increasing bed inventory pressure drops and solid concentration increase. The axial particle velocities slightly change with bed inventory. The comparison of simulation results with experimental measurements was resulted in good agreement (<5%) with both models. The simulation with EMMS drag model predicted the pressure profiles more accurately than Wen-Yu/Ergun drag model. The profiles of particle volume fraction and axial velocity demonstrate that core-annulus flow pattern was captured by both models. But EMMS drag model was better in revealing the meso-scale structures at instantaneous particle concentration distribution. Moreover, the influence of particle size distribution on particle volume fraction and particle velocity profiles is also investigated with two drag models.

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“…In the inlet and outlet section of a riser, however, the flow is highly anisotropic and 3D effects need to be accounted for to obtain reliable simulation results . Lately many researchers are focusing their computational work on the effect of the riser outlet geometry and often report contradictory trends . Shi et al highlight the importance of carefully specifying the riser outlet geometry in any riser modeling study.…”

Section: Introductionmentioning

confidence: 99%

“…Lately many researchers are focusing their computational work on the effect of the riser outlet geometry and often report contradictory trends . Shi et al highlight the importance of carefully specifying the riser outlet geometry in any riser modeling study. The Energy‐Minimization MultiScale (EMMS) model is reported by several researchers to be more adequate for simulations at the outlet, as the structural homogeneity assumption of traditional two‐fluid models does not hold for flow close to the outlet .…”

Section: Introductionmentioning

confidence: 99%

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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Effects of the riser exit geometries on the hydrodynamics and solids back-mixing in CFB risers: 3D simulation using CPFD approach

Cited by 37 publications

References 65 publications

Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed

Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed

Cold Flow Simulation of a 30 kWth CFB Riser with CPFD

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

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