MP-PIC simulation of circulating fluidized beds using an EMMS based drag model for Geldart B particles--颗粒学报PARTICUOLOGY

Dymala, T., Wytrwat, T., & Heinrich, S. (2021). MP-PIC simulation of circulating fluidized beds using an EMMS based drag model for Geldart B particles. Particuology, 59, 76-90. https://doi.org/10.1016/j.partic.2021.07.002

MP-PIC simulation of circulating fluidized beds using an EMMS based drag model for Geldart B particles

Timo Dymala ^*, Tom Wytrwat, Stefan Heinrich

Hamburg University of Technology, Institute of Solids Process Engineering and Particle Technology, Denickestr. 15, 21073 Hamburg, Germany

10.1016/j.partic.2021.07.002

Volume 59, December 2021, Pages 76-90

Received 31 March 2021, Revised 13 May 2021, Accepted 2 July 2021, Available online 28 July 2021, Version of Record 13 October 2021.

E-mail: timo.dymala@tuhh.de

Highlights

• Application of MP-PIC method to pilot-scale cold model circulating fluidized beds.

• Application of an EMMS based drag model for Geldart B particles.

• Major parameters of EMMS based drag model in good agreement with the experiments.

• EMMS model is able to predict a dense bottom zone.

Abstract

In this study the multiphase particle-in-cell (MP-PIC) method is used for the simulation of two pilot-scale circulating fluidized beds (CFBs) with quartz sand belonging to Geldart’s group B as bed material. The simulations were performed using a homogeneous drag model as well as a structure dependent drag model based on the energy minimization multi-scale method (EMMS). The results are compared with experimental data from literature as well as experiments. The simulations with the EMMS based drag model show a good agreement of the time-averaged axial solids concentration, circulation rate and riser pressure drop. Furthermore, a lower grid sensitivity is observed compared to the homogeneous drag model. In contrast to the conventional drag model a dense bottom zone is predicted by the EMMS based drag model. An overprediction of the solid concentration in the dense bottom zone is presumably due to an overprediction of the cluster diameter that is calculated using an empirical cluster diameter correlation. This shows the necessity for a new meso-scale cluster correlation for the simulation of Geldart B particles. Furthermore, the results of the time-averaged radial solids concentration differ from the expectations of a core-annulus flow indicating that a mesh refinement at the walls is necessary. Finally, the importance of using a realistic particle size distribution is identified.

Graphical abstract

Keywords

3D-CFD simulation; Circulating fluidized bed (CFB); Multiphase particle-in-cell method (MP-PIC); Energy minimizing multi-scale theory (EMMS); Validation study

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