Article

CFD simulation for two-phase mixing in 2D fluidized bed

International Journal of Advanced Manufacturing Technology (Impact Factor: 1.78). 01/2009; 45:1-4. DOI: 10.1007/s00170-008-1875-9

ABSTRACT Two-phase (solid and gas) 2D fluidized bed reactor’s flow pattern was investigated. Computational fluid dynamics (CFD) simulation
results were compared with those obtained experimentally. The CFD simulation is carried out using commercial software “Fluent”.
Experiment is carried out in a fluidized bed containing spherical glass beads of diameter 300–350μm. Initial volume fraction
is fixed as 0.6. A multi-fluid Eulerian model incorporating the kinetic theory for solid particles was applied in order to
simulate the gas–solid flow. Momentum exchange coefficients are calculated using Syamlal–O’Brien drag function. The kinetic
energy lost during inter-particle collisions were characterized by specifying the restitution coefficient values from 0.9
to 0.99. The pressure drop and bed expansion ratio for various superficial velocities are compared with experimental results.

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    ABSTRACT: The aim of this study is to develop a robust CFD model for predicting fluid dynamics in a gasification reactor. Experimental tests are performed. A cylindrical bed with pressure sensors is used in the experimental study. A series of simulations are performed using the commercial CFD tool ANSYS Fluent 12.1. A multi-fluid Eulerian model incorporating the kinetic theory of granular flow is applied in the simulations. Fluidized bed reactors in biomass gasification processes use steam as a fluidizing gas. High temperature makes it difficult to study the flow behaviour under the operating conditions. A cold flow model is constructed to study the fluid dynamics. Air at ambient conditions is used as the fluidizing gas for the cold model. The density and viscosity variation between air at ambient temperature and steam at high temperature results in different flow behaviour. The CFD model is developed to also be able to predict the flow behaviour of steam fluidized beds. Computational minimum fluidization velocity, bed expansion ratio pressure drop and pressure standard deviation agree well with experimental measurements. A computational model has been developed and validated against experimental data. The validated CFD-model can be useful in the study of flow behaviour of high temperature steam fluidized gasification reactors.
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