Simulation of coal combustion in a bubbling fluidized bed by distinct element method

Abstract

T he distinct element method (DEM) is used to model combustion of coal particles in a bubbling fluidized bed. The gas phase is modeled as a continuum and the particle phase is modeled by DEM. The chemical reactions consist of the heterogeneous reactions of char with O-2, CO, CO2, NO and N2O and in the homogeneous reactions involving CO, 02, NO and N2O. The colliding partic le-p article heat transfer is based on the analysis of the elastic deformation of the spheres during their contact. The model predicts the particle heterogeneous flow structure, the thermal characteristics of burning coal particles, and the gaseous emissions from a fluidized binary mixture. Results show that the instantaneous contribution of the collision heat transfer ranges from 0 to about 1.0% of the total heat transfer during the coal combustion. The mean excess of coal temperature is approximately 140K, and the maximum excess of coal particle temperature is approximately 270 K after 2 s.