Fluidization of spherocylindrical particles

Vinay V Mahajan,Tim M.J Nijssen,Jeroen Hofman,Johan T Padding,Barry W Fitzgerald,Hans Kuipers

doi:10.1051/epjconf/201714006019

Vinay V Mahajan, Tim M.J Nijssen + Show 4 more

Open Access

https://doi.org/10.1051/epjconf/201714006019

Copy DOI

Abstract

Multiphase (gas-solid) flows are encountered in numerous industrial applications such as pharmaceutical, food, agricultural processing and energy generation. A coupled computational fluid dynamics (CFD) and discrete element method (DEM) approach is a popular way to study such flows at a particle scale. However, most of these studies deal with spherical particles while in reality, the particles are rarely spherical. The particle shape can have significant effect on hydrodynamics in a fluidized bed. Moreover, most studies in literature use inaccurate drag laws because accurate laws are not readily available. The drag force acting on a non-spherical particle can vary considerably with particle shape, orientation with the flow, Reynolds number and packing fraction. In this work, the CFD-DEM approach is extended to model a laboratory scale fluidized bed of spherocylinder (rod-like) particles. These rod-like particles can be classified as Geldart D particles and have an aspect ratio of 4. Experiments are performed to study the particle flow behavior in a quasi-2D fluidized bed. Numerically obtained results for pressure drop and bed height are compared with experiments. The capability of CFD-DEM approach to efficiently describe the global bed dynamics for fluidized bed of rod-like particles is demonstrated.

Highlights

Non-spherical particles are frequently encountered in fluidisation processes such as in the production of biomass fuel in fluidised bed gasifiers [1]
The computational fluid dynamics (CFD)-discrete element method (DEM) model is developed on the Open Source coupling engine CFDEM, which allows for program execution for a user-prescribed number of time steps after which data is exchanged between the OpenFOAM fluid solver and the LIGGGHTS particle solver
We have presented results on the variation of pressure drop and bed height from computational fluid dynamics and discrete element method (CFD-DEM) simulations and experiments of the fluidisation of spherocylinder particles

Summary

Introduction

Non-spherical particles are frequently encountered in fluidisation processes such as in the production of biomass fuel in fluidised bed gasifiers [1]. Biomass particles are milled, resulting in particle shapes such as cylinders with an aspect ratio between 3 and 5. When fluidised, these particles experience anisotropic drag and lift conditions due to the surrounding fluid [2] and anisotropic interactions with adjacent particles and boundaries. The altered drag and collision characteristics directly affect the voids and heterogeneous structures, as well as mass and heat transfer rates. As such it is imperative to account for orientation, alignment and wall proximity effects in a description of particle collisions and the formulation of solid-fluid drag relations

Methods

Results

Conclusion