Comparison of Fully 3-D, Simplified 3-D and 2-D Numerical Simulations on a Circulating Fluidized Bed Boiler

Based on the fully three-dimensional (3-D) and two-dimensional (2-D) comprehensive CFD (Computational Fluid Dynamics) combustion models for a circulating fluidized bed boiler, a simplified 3-D computational domain considering the corrections of furnace side wall openings is proposed. It aims to compensate for the deficiencies of the large amount of computation in the fully 3-D model and improve the air and gas flow treatments at the openings in the simplified 2-D model. Three different computational domains, named as the fully 3-D model, simplified 3-D model and 2-D model, were implemented to perform a comparative CFD analysis in an ultra-supercritical circulating fluidized bed boiler including the hydrodynamics, penetration depth of secondary air, temperature and species distribution. The simulation results computed by the simplified 3-D model yield better agreement with the fully 3-D simulation results than those of the 2-D model. The simplified 3-D model is recommended as an alternative computational domain for the conventional 2-D model in the numerical simulation of large-scale circulating fluidized bed boiler.