Numerical simulation of circulating fluidized bed oxy-fuel combustion with Dense Discrete Phase Model

Computational fluid dynamics (CFD) has become a valuable tool to study the circulating fluidized bed (CFB) combustion process. This work conducts the CFB oxy-fuel combustion process with different O-2 concentrations by using the Dense Discrete Phase Model (DDPM) based on the Eulerian-Lagrangian concept, in which the gas is treated as a continuous phase whereas the solid is tracked in a discrete way. The effects of heat and mass transfer, gas-turbulence as well as the homogeneous and heterogeneous reactions are considered. Simulated results are analyzed both qualitatively and quantitatively in terms of particle flow structure, temperature, carbon conversion and gas composition. Results show that the physical and thermo-chemical properties of the coal particles with different diameters vary greatly, which illustrates the significant particle size distribution (PSD) effects on the simulated results. Besides, with the increase of the inlet O-2 concentration, the coal particles exhibit a different distribution of the flow structure and combustion characteristics due to both a decrease of the superficial gas velocity and an increase of the chemical reaction rate. The simulated results are well validated by the available experimental data, indicating the feasibility of the established DDPM for the CFB combustion process.