Hydrodynamics in commercial-scale internally circulating fluidized beds with different central downcomer outlets--颗粒学报PARTICUOLOGY

Meng, Z., Liu, M., Ahmad, N., Wang, W., & Lu, C. (2020). Hydrodynamics in commercial-scale internally circulating fluidized beds with different central downcomer outlets. Particuology, 51, 120-131. https://doi.org/10.1016/j.partic.2019.09.007

Hydrodynamics in commercial-scale internally circulating fluidized beds with different central downcomer outlets

Zhenliang Meng ^{a b}, Mengxi Liu ^a *, Nouman Ahmad ^b, Wei Wang ^{b c *}, Chunxi Lu ^a

a State Key Laboratory of Heavy Oil Processing, China University of Petroleum-Beijing, Beijing 102249, China
b State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
c University of Chinese Academy of Sciences, Beijing 100049, China

10.1016/j.partic.2019.09.007

Volume 51, August 2020, Pages 120-131

Received 25 July 2018, Revised 10 March 2019, Accepted 5 September 2019, Available online 16 December 2019, Version of Record 11 April 2020.

E-mail: mengxiliu@sina.com; wangwei@ipe.ac.cn

Highlights

• The flow inside ICFBs with different downcomer outlet is numerically investigated.

• The gas bypass is eliminated when the diameter of the conic baffle is 1.1 D_d.

• The solid circulation mass flux in ICFB increased by about 62.5% from model A to model C.

Abstract

Standpipes, or downcomers, are commonly used in fluidized beds to transport particles. The outlet structure of the downcomer greatly affects the performance of flow from it and even overall reactor performance. In this study, the hydrodynamics in commercial-scale internally circulating fluidized beds (ICFBs) with central downcomers having different outlet structures was investigated using computational fluid dynamics simulations with an energy minimization multi-scale drag model. The predicted results closely agreed with experimental data. Results showed that in an ICFB with a downcomer outlet directly open to the bed (model A), nearly 12.7% to 5.4% of the gas in the draft tube bypasses into the downcomer. In the ICFB models B and C with a conic baffle below the downcomer, the gas bypass is significantly weakened or even eliminated when the diameter of the conic baffle is 1.1 times that of the downcomer (model C). In addition, the solids circulation mass flux in ICFBs increased by about 62.5%, from 126.8 kg/(m2 s) in model A to 206 kg/(m2 s) in model C.

Graphical abstract

Keywords

Internally circulating fluidized bed; Downcomer outlet; EMMS; CFD; Particles flow

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