Flamelet LES of a swirl-stabilized multi-stream pulverized coal burner in air and oxy-fuel atmospheres with pollutant formation

Abstract

A large-eddy simulation of a swirl-stabilized multi-stream laboratory-scale pulverized coal burner designed specifically for oxy-fuel investigation is conducted using a three-mixture-fraction flamelet model, in which both NOx and SOx emissions are considered. The simulation results are compared to those in an air atmosphere and the available experimental data. The flame structures and pollutant formation mechanisms are analyzed in detail. The results show that the oxy-coal flame is narrower in the radial direction compared to the air-coal flame. Further, the particle clustering phenomenon can be observed in the oxy-fuel atmosphere. The distributions of the thermo-chemical quantities in different conditions are significantly different. For pollutant formation, the results show that NO is mainly formed around the quarl zone in an oxy-fuel atmosphere, while a large amount of NO is formed in the far downstream region in an air atmosphere. Although the instantaneous distributions of SOx are qualitatively similar in different conditions, they are quantitatively different due to the different oxygen partial pressure in the air and oxy-fuel atmospheres.