Particle motion in the CFB riser with special emphasis on PEPT-imaging of the bottom section

Chan, Chian W.; Seville, Jonathan; Yang, Zhiming; Baeyens, Jan

doi:10.1016/j.powtec.2009.08.019

Cited by 38 publications

(23 citation statements)

References 34 publications

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“…(20) As shown in Figure 13, the occupancy near the bottom is quite low implying that the particle does not reach the bottom often, which is in accordance with the low velocity shown in Figures 11 and 12. 20.…”

Section: Cylindrical 3-d Bed: Jet-in-fluidized-bedsupporting

confidence: 81%

Numerical and experimental study on spout elevation in spout‐fluidized beds

et al. 2011

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The effect of elevating the spout on the dynamics of a spout‐fluidized bed, both numerically and experimentally is studied. The experiments were conducted in a pseudo‐two‐dimensional (2‐D) and a cylindrical three dimensional (3‐D) spout‐fluidized bed, where positron emission particle tracking (PEPT) and particle image velocimetry (PIV) were applied to the pseudo‐2‐D bed, and PEPT and electrical capacitance tomography (ECT) to the cylindrical 3‐D bed. A discrete particle model (DPM) was used to perform full 3‐D simulations of the bed dynamics. Several cases were studied, that is, beds with spout heights of 0, 2, and 4 cm. In the pseudo‐2‐D bed, the spout‐fluidization and jet‐in‐fluidized‐bed regime, were considered first, and it was shown that in the spout–fluidization regime, the expected dead zones appear in the annulus near the bottom of the bed as the spout is elevated. However, in the jet‐in‐fluidized‐bed regime, the circulation pattern of the particles is affected, without the development of stagnant zones. The jet‐in‐fluidized‐bed regime was further investigated, and additionally the experimental results obtained with PIV and PEPT were compared with the DPM simulation results. The experimental results obtained with PIV and PEPT agreed mutually very well, and in addition agreed well wtih the DPM results, although the velocities in the annulus region were slightly over predicted. The latter is probably due to the particle‐wall effects that are more dominant in pseudo‐2‐D systems compared with 3‐D systems. In the jet‐in‐fluidized‐bed regime, the background gas velocity is relatively high, producing bubbles in the annulus that interact with the spout channel. In the case of a non elevated spout, this interaction occurs near the bottom of the bed. As the spout is elevated, this interaction is shifted upwards in the bed, which allows the bubbles to remain undisturbed providing the motion of the particles in the annulus near the bottom of the bed. As a result, no dead zones are created and additionally, circulation patterns are vertically stretched. These findings were also obtained for the cylindrical 3‐D bed; although, the effects were less pronounced. In the cylindrical 3‐D bed the PEPT results show that the effect on the bed dynamics starts at hspout =1 4 cm, which is confirmed by the ECT results. Additionally, ECT measurements were conducted for hspout =1 6 cm to verify if indeed the effect happens at larger spout heights. The root mean square of the particle volume fraction slightly increased at hspout =1 2 cm, whereas a larger increase is found at hspout = 4 and 6 cm, showing that indeed more bubbles are formed. The presented results have not been reported so far and form valuable input information for improving industrial granulators. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2524–2535, 2012

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Section: Cylindrical 3-d Bed: Jet-in-fluidized-bedsupporting

confidence: 81%

Numerical and experimental study on spout elevation in spout‐fluidized beds

et al. 2011

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“…In the riser with abrupt 'L' and 'T' exits, the flow shows a trend similar to fast fluidization with a dense bottom, where intense back-mixing of particles have been frequently reported [64,67,71]. More specifically, in the riser with any types of exits, the newly-formed dense clusters near the wall area tend to flow downward due to the insufficient support from the gas in this area, and this downward motion of particles can contribute to the solids back-mixing, which has been shown and discussed in Fig.…”

Section: Effects Of Riser Exit On Solids Back-mixingmentioning

confidence: 66%

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

Shi

Lan

et al. 2015

Powder Technology

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“…[32]. To distinguish the two different cases easily, we will call the case of Sshaped solids holdup distribution as a "classical" fast bed (G s > G s rb ), while call the case of exponentially decayed solids holdup as a "premature" fast bed (G s ≤ G s rb ).…”

Section: Thermal Power Plants -New Trends and Recent Developments 130mentioning

confidence: 99%

Introductory Review on an Engineering Approach for Fast‐Bed Modeling in Mimic to Bubbling Bed Practice

Zhang¹,

Zhang²

2018

Thermal Power Plants - New Trends and Recent Developments

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Based on the downward-penetrating particle flow through clusters and the analogy between a falling cluster and a rising bubble identified by the authors, a "type-Achoking-oriented separate-phase-coexistence model" for the upper dilute region of fast beds was established first. Without any model parameter adjustment, the unified model predicted successfully the type C choking, the solids holdup of upper dilute region, and transitions to the high-density fast bed and the dense suspension up-flow.The model was then integrated with the sub-models of "cluster rebound at the dense bottom,"" the momentum flux balances for acceleration and transition zones" in the lower and middle parts of the bed. The integrated model predicted successfully the axial solids holdup distributions of literature data under extremely wide operation conditions covering dilute-phase transportation, the premature fast bed, the classical fast bed, and the high-density fast bed.

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Particle motion in the CFB riser with special emphasis on PEPT-imaging of the bottom section

Cited by 38 publications

References 34 publications

Numerical and experimental study on spout elevation in spout‐fluidized beds

Numerical and experimental study on spout elevation in spout‐fluidized beds

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

Introductory Review on an Engineering Approach for Fast‐Bed Modeling in Mimic to Bubbling Bed Practice

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