Impact of tangential burner firing angle on combustion characteristics of large scale coal-fired boiler

Abstract

Combustion characteristics in large scale boilers are influenced by a number of factors such as coal properties and burner operating conditions. Burner firing angle for example, will affect the fireball size and locations of heat release which affect the formation of ash slagging in a tangentially fired furnace. In this study, a computational fluid dynamics (CFD) simulation of coal combustion in a tangentially fired 700 MW power plant was developed to investigate the impact of burner firing angles on the flame profile in the furnace. The model was developed based on the two-phase flow model, coal devolatilization, char burnout model, discrete particle tracking and radiation heat transfer. The firing angles were changed by ±5° from the base angle of 43° and 55°. The study shows that firing angles have significant effect on the size of the flame fireball and the concentric fireball arrangement. Increasing the firing angle resulted in a larger fireball size with a region of low temperature at the core of the fireball. The simulation also shows that the flow profile becomes more stable with increasing firing angle, regardless of burner elevations. The results presented in this paper may enhance the understanding the complex relation between burner operating condition such as firing angle on flow patterns and combustion processes in a tangentially fired boilers.