(647c) Particle-Scale Investigations of Reactive Fluidized Beds Based on CFD-DEM Coupling Methods

Fluidized beds have been widely used in the industrial applications of solid fuel energy conversion. Though efforts have been taken to investigate reactive fluidized beds under various conditions, there is still a lack of thorough understanding on the interplays among the gas-solid hydrodynamics, heat transfer, and chemical reactions. It is noted that most previous numerical studies on the reactive fluidized beds were based on the continuum-based simulations, in which it is difficult to arrive the particle-scale information. In comparison, the simulation based on the computational fluid dynamics (CFD) - discrete element method (DEM) can give predictions with higher accuracy and resolution, which facilitates in-depth analysis on the fluidized beds.

A computational framework of CFD-DEM for the dense reactive gas-solid flow has been developed. The models are first validated against a series of experiments, which shows good agreement between the predictions and measurements. In this study, three typical reactive applications operated under the bubbling fluidization regime are investigated, namely the (i) biomass fast pyrolysis, (ii) coal gasification and (iii) coal combustion. The results show that different fluidized bed applications show distinct patterns of particle entrainment, gas-solid mixing and heat transfer. The effect of the gas-solid mixing on the performance of the reactor is emphasized. The chemical reactions in turn affects the gas-solid hydrodynamics by interphase mass transfer.