Modeling of Wall-to-Bed Heat Transfer in a Supercritical Water Fluidized Bed by the Packet Approach

Zhang, Tianning; Lu, Youjun

doi:10.1021/acs.iecr.0c04451

Cited by 9 publications

(5 citation statements)

References 49 publications

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“…The contact time decreased rapidly at first and then kept a stable value with the increase of the gas velocity. 12 Zhang and Lu 12 illuminated that the packet contact time achieved a constant value owing to a relatively stable bubble frequency. Molerus et al 13 disclosed that the mean packet contact time manifested as the reciprocal of the bubble frequency.…”

Section: = + + H H H Hmentioning

confidence: 99%

“…Yao et al found the decreased packet fraction attributed to the increase of bubble frequency near the wall. The contact time decreased rapidly at first and then kept a stable value with the increase of the gas velocity . Zhang and Lu illuminated that the packet contact time achieved a constant value owing to a relatively stable bubble frequency.…”

Section: Introductionmentioning

confidence: 96%

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Bed-to-Wall Contact Dynamics in a Gas–Solid Fluidized Bed with Downward Solid Movement

Lin,

Li,

Zhang

et al. 2024

Ind. Eng. Chem. Res.

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The bed-to-wall contact dynamics present a significant effect on heat transfer performance according to the packet renewal model proposed by Mickley and Fairbanks [Mechanism of heat transfer to fluidized beds. AIChE J. 1955 1 (1), 374−384]. However, the systematical investigations on contact dynamics are scarce, especially in a pilot-scale fluidized bed with downward solid movement. Therefore, a pilot-scale experimental setup was constructed to study the hydrodynamics behavior and contact dynamics in a gas−solid fluidized bed with downward solid movement, a configuration typical in catalyst coolers in the FCC process. Results indicate that the coupling of downward solid movement can break up large bubbles in turbulent fluidization, leading to a small bubble size and a high bubble frequency near the immersed surface. Moreover, the downward solid movement increases the contact distance between the packet and the immersed surface in the bubbling fluidization. The packet renewal model is modified by introducing local and global packet contact time. An empirical correlation was provided to predict the contact distance by considering the impact of solid radial mixing, solid particle size, and solid mass flux.

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Section: = + + H H H Hmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Bed-to-Wall Contact Dynamics in a Gas–Solid Fluidized Bed with Downward Solid Movement

Lin,

Li,

Zhang

et al. 2024

Ind. Eng. Chem. Res.

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show abstract

“…Among these reactors, the supercritical water fluidized bed reactor (SCWFB) shows good performance [9] because it has the advantages of high heat and mass transfer rates, thus, achieving continuous and efficient gasification of high concentration coal slurry and showing good prospects for commercial applications [10][11][12]. Matsumura and Minowa [8] first introduced a fluidized bed into the SCWG for wet biomass gasification.…”

Section: Introductionmentioning

confidence: 99%

Efficient Surrogate-Assisted Parameter Analysis for Coal-Supercritical Water Fluidized Bed Reactor with Adaptive Sampling

et al. 2023

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Supercritical water fluidized beds (SCWFBs) are promising and efficient reactors for the gasification of coal in supercritical water. The understanding and investigation of multi-phase flows as well as the gasification process usually rely on time-consuming experiments or numerical simulations, which prohibit fast and full exploration of the single and coupled effects of the operation and geometric parameters. To this end, this paper builds an efficient surrogate-assisted parameter analysis framework for the SCWFB reactor. Particularly, (1) it establishes a steady numerical simulation model of the SCWFB reactor for the subsequent analysis; and (2) it employs a Gaussian process surrogate modeling via efficient adaptive sampling to serve as an approximation for predicting the carbon conversion efficiency (CE) of the reactor. Based on this parameter analysis framework, this paper investigates the effects of five independent parameters (the mass flow rate of supercritical water, mass flow rate of the coal slurry, temperature of supercritical water, temperature of the outer wall and reactor length) and their interactions on the reaction performance in terms of the carbon conversion efficiency (CE). We found that the CE increases as a function of the temperature of supercritical water, the temperature of the outer wall and the reactor length; while it decreases as a function of the mass flow rate of supercritical water and the mass flow rate of the coal slurry. Additionally, the global sensitivity analysis demonstratesthat the influence of the temperature of the outer wall exerts a stronger effect than all the other factors on the CE, and the coupled interaction among parameters has a slight effect on the CE. This research provides useful guidance for scaled-up designs and optimization of the SCWFB reactor.

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“…A simplified spherical particle model was used to describe the thermal resistance between the wall and the packet. Then, the heat transfer coefficients of the models based on the packet renewal theory were compared with those of the empirical correlation method [22].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of The Temperature Characteristics of a Coal—Supercritical Water-Fluidized Bed Reactor for Hydrogen Production

et al. 2023

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Supercritical water gasification (SCWG) of coal is a promising clean coal technology, which discards the traditional coal combustion and oxidation reaction to release carbon dioxide and other pollutants and replaces coal with a gasification reduction reaction in supercritical water to finally convert coal into a hydrogen-rich gas product with no net carbon dioxide emissions and no pollutant emissions, and thus has received much attention in recent years. However, the experimental conditions of coal to the hydrogen reactor are harsh, costly, and not easy to visualize and analyze, so numerical calculation and simulation analysis are important for the design, optimization, and industrial scaling-up of the reactor. In order to study the effect of the temperature field on the hydrogen production rate of the coal supercritical water gasification hydrogen production reactor, a numerical simulation calculation model is developed for this reactor in this paper. Comparing the experimental data in the literature, the maximum relative error of the gasification product yield per kg of coal between the two is less than 5%, which verifies the accuracy of the model built and the numerical method adopted in this paper. On this basis, the effects of supercritical water temperature and coal slurry temperature on the reactor’s gasification products and reaction rate were investigated in depth. The results show that increasing the supercritical water temperature is beneficial to improve the reactor hydrogen production efficiency, while the high coal slurry temperature is not conducive to adequate reaction, thus reducing the hydrogen production efficiency. For the laboratory coal supercritical water gasification to hydrogen reactor studied in this paper, the ideal temperature of supercritical water is 850~900 K, and the ideal temperature of coal slurry is 400–450 K. The conclusions of this paper can provide some reference for subsequent industrial scale-up studies of the reactor.

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Modeling of Wall-to-Bed Heat Transfer in a Supercritical Water Fluidized Bed by the Packet Approach

Cited by 9 publications

References 49 publications

Bed-to-Wall Contact Dynamics in a Gas–Solid Fluidized Bed with Downward Solid Movement

Bed-to-Wall Contact Dynamics in a Gas–Solid Fluidized Bed with Downward Solid Movement

Efficient Surrogate-Assisted Parameter Analysis for Coal-Supercritical Water Fluidized Bed Reactor with Adaptive Sampling

Numerical Analysis of The Temperature Characteristics of a Coal—Supercritical Water-Fluidized Bed Reactor for Hydrogen Production

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