CFD simulation of smooth and T-abrupt exits in circulating fluidized bed risers

• Published in: Particuology Vol. 8; no. 4; pp. 343 - 350
• Main Authors: Wu, Xuezhi, Jiang, Fan, Xu, Xiang, Xiao, Yunhan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2010; Graduate University of the Chinese Academy of Sciences,Beijing 100049,China%Key Laboratory of Advanced Energy and Power,Institute of Engineering Thermophysics,Chinese Academy of Sciences,Beijing 100190,China; Key Laboratory of Advanced Energy and Power,Institute of Engineering Thermophysics,Chinese Academy of Sciences,Beijing 100190,China
• Subjects: CFB; CFD模拟; Circulating; Computational fluid dynamics; Computer simulation; Drag force; EMMS drag force model; Fluidized beds; Gas–solid flow; Mathematical models; Risers; Sand; Smooth exit; T-abrupt exit; 出口结构; 实验室规模; 指数曲线; 气固循环流化床; 计算流体力学; 阻力模型; Gas–solid flow; T-abrupt exit; EMMS drag force model; CFB; Smooth exit; Gas-solid flow
• ISSN: 1674-2001; 1672-2515; 2210-4291
• DOI: 10.1016/j.partic.2010.01.007

Gas-solid flow in circulating fluidized bed （CFB） risers depends not only on operating conditions but also on exit configurations. Few studies investigated the effects of exit configurations on flow structure using computational fluid dynamics （CFD）. This paper provides a 2D two-fluid model to simulate a cold bench-scale square cross-section riser with smooth and T-abrupt exits. The drag force between the gas and solid phases plays an important role in CFD. Since the drag force model based on homogeneous two- phase flow, such as the Wen-Yu correlation, could not capture the heterogeneous structures in gas-solid flow, the structure-dependent energy-minimization multi-scale （EMMS） drag force model （Wang, Ge, ＆ Li, 2008）, applicable for Geldart B particles （sand）, was integrated into the two-fluid model. The calculated axial solids hold-up profiles were respectively exponential curve for smooth exit and C-shaped curve for T-abrupt exit, both consistent with experimental data. This study once again proves the key role of drag force in CFD simulation and also shows the validity of CFD simulation （two-fluid model） to describe exit effects on ~as-solid flow in CFB risers.