Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds

doi:10.1007/s11705-020-1953-6

Front. Chem. Sci. Eng.

2021, Vol. 15

Issue (3) : 579-590 https://doi.org/10.1007/s11705-020-1953-6

RESEARCH ARTICLE

Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds

Shanwei Hu¹, Xinhua Liu^1,²(

)

¹. State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
². Dalian National Laboratory for Clean Energy, Dalian 116023, China

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Abstract

Dual-loop circulating fluidized bed (CFB) reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability. However, the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms, meaning it has been heavily based on empiricism and stepwise experiments. Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them. This article proposed a general method for modeling multi-loop CFB systems by utilizing the energy minimization multiscale (EMMS) principle. A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors, to achieve the mass conservation and pressure balance in each circulation loop. Based on the modularization strategy, corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor. This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering.

Keywords multi-loop circulating fluidized bed mathematical modeling energy minimization multiscale virtual fluidization mesoscale structure

Corresponding Author(s): Xinhua Liu

Just Accepted Date: 28 July 2020 Online First Date: 21 September 2020 Issue Date: 10 May 2021

Cite this article:

Shanwei Hu,Xinhua Liu. Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds[J]. Front. Chem. Sci. Eng., 2021, 15(3): 579-590.

URL:

https://academic.hep.com.cn/fcse/EN/10.1007/s11705-020-1953-6
https://academic.hep.com.cn/fcse/EN/Y2021/V15/I3/579

Fig.1 The EMMS model and its extensions.

Component	Literature	Correlations
Cyclone	[24]	$Δ p cy = 0.5 ζ ? ρ g u cy 2$
Gas distributor	[25]	$Δ p gd = ? 0.5 ζ ρ g u 02 / g$
Connection pipe	[26]	$Δ p cp = ρ p (1 − ε) g H + 0.057 G s g L g D + G s 2 2 ρ p$
Butterfly valve	[27]	$Δ p v = 1 2 ρ v (1 − ε mf) ? (G sv C d φ) 2$

Tab.1 Correlations for other typical CFB components

Fig.2 Computation scheme for multi-loop CFB systems.

Fig.3 Typical windows in the software: (a) module definition; (b) project creation.

Fig.4 Flow chart of the software Virtual Fluidization v1.0.

Fig.5 Modeling and visualization of steady-state hydrodynamics in an industrial-scale CFB system: (a) schematic of the CFB system adapted from Herbert and Reh [28]; (b) project creation for the full-loop modeling of the CFB system; (c) dynamic display of solids concentration distribution at various gas velocities.

Fig.6 Schematic diagram of the dual-loop CFB reactor adapted from Wang [2].

Fig.7 Influence of the superficial gas velocity in section I on solids circulating rates.

Fig.8 Influence of the superficial gas velocity in section I on pressure drops.

Fig.9 Axial voidage profile in the riser under different operating conditions.

Fig.10 Radial voidage distribution in the riser: (a) radial voidage profile at various heights; (b) error analyses.

a	acceleration, m?s^?2
C_d	constant
D	diameter, m
d_b	bubble diameter, m
f	volume fraction of the clusters
f_b	volume fraction of the bubble phase
G_s	solids circulation rate or solids flux, kg?m^?2?s
g	gravity acceleration, m?s^?2
H	height, m
I_m	solid inventory, kg
M_s	mass flow rate, kg?s^?1
N_gs, N_st	mass-specific energy dissipation rate for suspending and transporting particles, J?kg^?¹?s
N_gs0, N_st0	normalized N_gs or N_st
N_T	total energy dissipation rate with respect to unit mass of particles, J?kg^?1?s
r, R	radius, m
U_s	superficial velocity, m?s^?1
W_gs, W_st	volume-specific energy dissipation rate for suspending and transporting particles, J?m^?3?s
$Δ p$	pressure drop, kPa
$ε ‾ r$	average voidage between zero and r
e	voidage
j	degree of valve opening
m	shear viscosity, Pa?s
r	density, kg?m^?3
t	interfacial shear stress, N?m^?²
z	empirical coefficient

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