Effect of Air Distribution on Aerodynamic Field and Coal Combustion in an Arch-Fired Furnace

Abstract

In this paper, the influence of air distribution on aerodynamic field and combustion performance in a 0.9 MW arch-fired furnace has been investigated by analyzing the momentum ratio of air flows and the air stoichiometric ratio in the preceding stage combustion zone. It is found that the momentum ratio of air−fuel flows directly affects the arch air penetration length and the position of the flame center, which is critical to the temperature distribution in the furnace and on the furnace walls. The best combustion performance in the experimental range occurs when the momentum ratio of arch air to secondary air equals 1.34 and that of arch air to D&E-layer secondary air equals 4.42. In addition, it is found that the heat loss due to incomplete combustion, also called combustible loss, and NOx emission in the flue gas are related to the air stoichiometric ratio (SR). The minimum values of unburned carbon in fly ash, unburned carbon in the slag and NOx emission at the furnace outlet are attained when SR = 0.67, 0.63, and 0.59, respectively. Furthermore, both combustible loss and NOx emission obtain proper values simultaneously when SR = 0.634, which could be considered as the optimum operation condition.