Effects of coal particle size on the two-phase flow and slagging performance in a swirl burner

Abstract

Swirl burner is widely used in coal-fired boilers. Coal particle size is an important factor affecting the two-phase flow as well as the combustion performances of a swirl burner. A bench-scale experiment with CFD simulation was conducted with full burner complexity. The results show that asymmetry of the particle phase is gradually weakened as the particle size increases, opposite to the variation trend of the continuous flow field in a hot state. The asymmetry of the particle phase is much more affected by the asymmetry of the secondary air jet flow than that of the primary air jet flow. As the particle size increases within a certain range, the combustibility of pulverized coal decreases, which enhances the asymmetry of the continuous flow field. When the particle size increases more than 50 μm, an increase in the concentration of incomplete combustion particles in the side recirculation zone around the burner occurs, intensifying the tendency of slagging. Thus, controlling the pulverized coal particle size below 50 μm is a considerable choice to improve combustion efficiency and avoid slagging.