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Flow characteristics of circulating fluidized beds near terminal velocity: Eulerian model of a lab-scale apparatus

Author:
Jalali, Payman, Nikku, Markku, Ritvanen, Jouni, Hyppänen, Timo
Source:
Powder technology 2018 v.339 pp. 569-584
ISSN:
0032-5910
Subject:
fluidized beds, hydrodynamics, models, powders, terminal velocity
Abstract:
The hydrodynamic characteristics of gas and solid flows in circulating fluidized beds (CFB) can also influence other processes. To investigate various features of flows and mass circulation in CFB, a computational study was performed with the support of experiments measured in the riser section of a lab-scale apparatus of CFB. The fluidization velocity was slightly below the terminal velocity to avoid a major solid entrainment. The Gidaspow's model was used to calculate the gas-solid drag term in computational cells, which led to a good agreement with the experimental data of pressure profile. The gas inlet conditions were shown to be uninfluential in the hydrodynamics of major part of the upper riser, and the solid inlet (return) imposed non-uniformity in radial and tangential directions. The time-averaged profiles presented a good indication of the wall layer formation. The rate of circulating mass in the riser from simulations was obtained 25% lower than the experiments. The coefficient of restitution was a parameter with notable influence on the hydrodynamics and the present study suggests that a variable coefficient of restitution in Eulerian models can describe the behavior of CFB system more accurately.
Agid:
6114203