Hydrodynamic Characteristics in a Cold Flow Model of Quadruple Fluidized Bed Gasifier

Ren, Jie; Wang, Ziliang; He, Boshu; Yan, Linbo; Wang, Ziqi; Ding, Guangchao; Ying, Zhaoping

doi:10.1021/acs.iecr.9b06116

Cited by 2 publications

(9 citation statements)

References 23 publications

(48 reference statements)

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“…This sudden change of the flow direction causes a separation of sand from its main entrained flow. The separated amount of sand then collides with the riser ceiling, falls, and mixes with the upward flow of particles near the riser sidewalls 29 …”

Section: Resultsmentioning

confidence: 99%

“…The sand entrainment from the riser could represent the global sand circulation rate (SCR) of the DFBG system 13 . By determining the accumulating time of sand in a specified segment of the cyclone downcomer when the airflow to the ULS had been paused/shut off, the SCR from the riser to the ULS could be calculated based on the filled‐up height, the bulk density of sand, and the measured time 27‐29 . The airflow to the ULS was then reopened, leading to the resumption of the ULS bed fluidization and the releasing flow of the accumulated sand to the gasifier under the normal system operation.…”

Section: Materials and Methodologymentioning

confidence: 99%

“…a 3D perspective model of the DFB cold flow system along with its main devices the filled-up height, the bulk density of sand, and the measured time. [27][28][29] The airflow to the ULS was then reopened, leading to the resumption of the ULS bed fluidization and the releasing flow of the accumulated sand to the gasifier under the normal system operation.…”

Section: Experimental Workmentioning

confidence: 99%

“…The separated amount of sand then collides with the riser ceiling, falls, and mixes with the upward flow of particles near the riser sidewalls. 29 Besides, the piling-up or accumulating flow of sand occurring in the cyclone downcomer fills up this zone and blocks the entrainment sand flow from the riser to the downstream units (Figure A2D). This phenomenon can occur in the system because of either the excessive airflow rate in the riser or the low air aeration rate in the ULS.…”

Section: Undesirable Phenomenamentioning

confidence: 99%

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Effect of sand particle size on the hydrodynamics of a dual fluidized bed cold flow system applied for waste‐to‐energy gasifiers

Dinh

Hsiau

et al. 2022

Intl J of Energy Research

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Summary Since the dual fluidized bed (DFB) system has been increasingly adopted for waste‐to‐energy gasification, a three‐dimensional computational fluid dynamics full‐loop model of a DFB cold flow system has been developed to predict the pressure and sand circulation rate (SCR) under various operating conditions. The pressure data were recorded at 18 specified points along the system height. In addition, the SCRs were determined at the two crucial positions connecting the riser and the gasifier and vice versa. The simulation results were then validated against the experimental data, taking into account the effects of the sand particle size (ds), the air inlet velocity in the riser (v0,riser), and the initial gasifier bed height (h0,gasifier). It could be observed in the riser that the flow structures of the smaller ds(s) were almost scattering patterns, while those of the bigger ones were mainly clusters. Compared with bigger ds(s), more homogeneous pressure distributions in the riser and higher bed expansion in the gasifier were obtained with smaller ones. A compromise between the system performance and pre‐treating cost for the feedstock particle sizes should be considered further to achieve the best system performance. On the other hand, the increases of the v0,riser and the h0,gasifier enhanced the gasifier bed pressure, facilitating the downward sand flow back to the riser via the LLS. Although some minor discrepancies existed between the simulation and experimental data, the predicted tendencies agreed well with the measured ones. It was also found that a system operating with ds = 500 μm, at v0,riser = 4.0 m/s and h0,gasifier = 0.25 m yielded stable flow characteristics and optimal global SCR. Moreover, some unexpected phenomena predicted and verified with the experimental observations could be avoided or minimized using suitable particle sizes of the feedstock and operating parameters. In sum, the better validation results with lower errors than our previous study, the more reasonable air‐sand flow patterns, and the substantial predictions of undesirable problems are the significant improvements of this study, providing valuable information for effectively designing and operating the practical DFB hot flow systems. Novelty Statement This study developed a 3D computational fluid dynamics full‐loop model of a DFB cold flow system for predicting the pressure and sand circulation rates under various operating conditions of particle size, inlet velocity, and initial bed height. The better validation results against the experimental data, the more reasonable air‐sand flow patterns, and the substantial predictions of undesirable problems are the significant improvements of this study, providing helpful information for designing and operating the DFB hot flow gasifiers.

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Section: Resultsmentioning

confidence: 99%

Section: Materials and Methodologymentioning

confidence: 99%

Section: Experimental Workmentioning

confidence: 99%

Section: Undesirable Phenomenamentioning

confidence: 99%

See 2 more Smart Citations

Effect of sand particle size on the hydrodynamics of a dual fluidized bed cold flow system applied for waste‐to‐energy gasifiers

Dinh

Hsiau

et al. 2022

Intl J of Energy Research

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“…Inspired by the advantage of the circulating fluidized bed, the dual fluidized bed (DFB) conversion technologies are proposed, which have a characteristic of using two fluidized bed (FB) reactors that are interconnected with circulated heat carrier particles for higher heating rates [21][22][23][24][25][26][27][28]. Based on the DFB technology, quadruple fluidized bed (QFB) system regarded as a cost-effective method is proposed [29][30][31][32]. However, it still belongs to the external circulating system, which may lead to an increase in the equipment costs and reduction in heat transfer efficiency to a certain extent.…”

Section: Introductionmentioning

confidence: 99%

Fluid Dynamics Investigation in a Cold Flow Model of Internal Recycle Quadruple Fluidized Bed Coal Pyrolyzer

Cao,

Yu,

Wang

et al. 2024

Processes

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Internal recycle quadruple fluidized bed pyrolyzer (IR-QFBP) consists of a dual fluidized bed pyrolyzer and a dual fluidized bed combustor and is proposed in this work. It is a new kind of efficient fluidized bed with high pyrolysis and energy efficiency. IR-QFBP may attract extensive attention because of its compact structure. Cold hydrodynamic characteristics of IR-QFBP are the bases of modeling and designing for the hot one. To fully understand the hydrodynamic characteristics of IR-QFBP, a cold flow model on a laboratory scale was designed and set up; furthermore, the two-fluid model (TFM) based simulation was also carried out. The pressure profiles, fluidization states, velocity profiles, and circulation rates of a solid powder at different operation conditions in IR-QFBP were investigated. The results showed that the stable internal circulation of solid powder can be achieved in IR-QFBP. And different circulation characteristics can be obtained by adjusting the operating conditions.

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Hydrodynamic Characteristics in a Cold Flow Model of Quadruple Fluidized Bed Gasifier

Cited by 2 publications

References 23 publications

Effect of sand particle size on the hydrodynamics of a dual fluidized bed cold flow system applied for waste‐to‐energy gasifiers

Effect of sand particle size on the hydrodynamics of a dual fluidized bed cold flow system applied for waste‐to‐energy gasifiers

Fluid Dynamics Investigation in a Cold Flow Model of Internal Recycle Quadruple Fluidized Bed Coal Pyrolyzer

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