Two and three dimensional modeling of fluidized bed with multiple jets in a DEM

Deb, S., & Tafti, D. K. (2014). Two and three dimensional modeling of fluidized bed with multiple jets in a DEM–CFD framework. Particuology, 16, 19–28. https://doi.org/10.1016/j.partic.2014.04.005

Two and three dimensional modeling of fluidized bed with multiple jets in a DEM–CFD framework

Surya Deb, Danesh K. Tafti^*

Randolph Hall (114 I), Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA

10.1016/j.partic.2014.04.005

Volume 16, October 2014, Pages 19-28

Received 17 December 2013, Revised 2 April 2014, Accepted 2 April 2014, Available online 27 June 2014.

E-mail: dtafti@vt.edu

Highlights

• 2D and 3D simulations were performed and validated with experiment for a multiple jet fluidized bed.

• 3D simulations could predict the bubble characteristics far away from the distributor plate.

• 2D simulations show good validation with experiment closer to the distributor plate.

• A full 3D simulation with time averaged results for multiple jets has not been published before.

Abstract

Fluidized beds with multiple jets have widespread industrial applications. The objective of this paper is to investigate the jet interactions and hydrodynamics of a fluidized bed with multiple jets. Discrete element modeling coupled with in-house CFD code GenIDLEST has been used to simulate a bed with nine jets. The results are compared with published experiments. Mono dispersed particles of size 550 μm are used with 1.4 times the minimum fluidization velocity of the particles. Both two and three dimensional computations have been performed. To the best of our knowledge, the results presented in this paper are the first full 3D simulations of a fluidized bed performed with multiple jets. Discrepancies between the experiment and simulations are discussed in the context of the dimensionality of the simulations. The 2D solid fraction profile compares well with the experiment close to the distributor plate. At higher heights, the 2D simulation over-predicts the solid fraction profiles near the walls. The 3D simulation on the other hand is better able to capture the solid fraction profile higher up in the bed compared to that near the distributor plate. Similarly, the normalized particle velocities and the particle fluxes compare well with the experiment closer to the distributor plate for the 2D simulation and the freeboard for the 3D simulation, respectively. A lower expanded bed height is predicted in the 2D simulation compared to the 3D simulation and the experiment. The results obtained from DEM computations show that a 2D simulation can be used to capture essential jetting trends near the distributor plate regions, whereas a full scale 3D simulation is needed to capture the bubbles near the freeboard regions. These serve as validations for the experiment and help us understand the complex jet interaction and solid circulation patterns in a multiple jet fluidized bed system.

Graphical abstract

Keywords

Discrete element modeling; Fluidized beds; Solid fraction; Bed height; Grid zone; Multiple jets; Particle flux

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