(112e) EMMS Application in 3D Full Loop Circulating Fluidized Bed Simulation

Flows inside circulating fluidized beds (CFBs) are inherently multiphase, involving at least one fluid phase and one solid phase. Accurate modeling is significant for the beds design, optimization, operation and scaling. Computational fluid dynamics (CFD) simulation is an efficient tool, since it is able to obtain flow dynamics in detail. The simulation accuracy is determined by many factors, drag model is a crucial one, which dominates the particle transport and internal recirculation in the system. Most drag models are conventional drag models, only true for homogeneous flow, but in the CFB system, especially in the dense region, the flow is heterogeneous, including bubbles, clusters etc., such meso-scale structures. To resolve these, new models are needed. Energy minimization multi-scale (EMMS) drag model has been found successful in correcting the drag and predicting the flow distribution in CFBs.

In this study, EMMS drag models, obtained based on the specific operating conditions and geometries, taking into account both local slip velocity and voidage, are coupled with CPFD (computational particle fluid dynamics) software Barracuda, to simulate two pilot scaling full loop three-dimensional CFBs, one with rectangular, the other with annular combustion chamber, to investigate the details inside respectively. The simulation results are analyzed in terms of full loop pressure drop, particle volume fraction distribution and particle circulation flux, etc., and compared with available experimental data. Through these, it can give guidance to the beds design and optimization.