### Abstract

A Eulerian multiphase model was used to study the
hydrodynamics of the gas–solids flow in a circulating
fluidized bed (CFB) furnace. Alternative modeling
approaches were tried to evaluate their effects on the
predicted solids distribution in the furnace. Due to high
computational costs, large scale calculations are
commonly performed by using a coarse mesh, which leads to
too uniform solids flow field and an overestimated
gas–solid drag force. Thus, a suitable form of correction
of the gas–solid drag is needed for coarse mesh
simulations. This study presents fluid dynamics
simulations of a 235 MWe CFB furnace by two sets of
interphase momentum exchange coefficients: the model
based on the homogeneous flow condition and the model
based on the energy-minimization multi-scale (EMMS)
approach. The calculations with one solid phase included
studies with two mesh resolutions and different particle
sizes. Additional simulations were performed using two
solid phases and four solid phases to analyze the effect
of polydispersity of particles. The model results were
compared with the measured vertical pressure profile of
the furnace and the locally measured solid concentration
and velocity profiles. The results show that with a
homogeneous model, the model matches better with
measurements if the mesh resolution is finer. The EMMS
approach can be used to improve the calculations in a
coarse mesh if the average particle size can be
determined correctly for the model. With multiple solid
phases, the vertical and horizontal segregation could be
simulated. However, increasing the number of solid phases
did not change the total solid concentration and pressure
profiles if the Sauter mean diameter of the total system
was constant. The results indicate that with a coarse
mesh, similar drag corrections would be necessary between
the solid phases that have been developed for gas-solid
drag.

Original language | English |
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Pages (from-to) | 239-249 |

Journal | Powder Technology |

Volume | 274 |

DOIs | |

Publication status | Published - 2015 |

MoE publication type | A1 Journal article-refereed |

### Keywords

- fluidization
- circulating fluidized bed
- computational fluid dynamics
- Eulerian approach
- drag force

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## Cite this

Shah, S., Myöhänen, K., Kallio, S., Ritvanen, J., & Hyppänen, T. (2015). CFD modeling of gas-solids flow in a large scale circulating fluidized bed furnace.

*Powder Technology*,*274*, 239-249. https://doi.org/10.1016/j.powtec.2015.01.019