Study on application of new type HBC-SSA burners with low NO_x emissions in a lean coal fired boiler

The mechanism of NO_x formation in pulverised coal combustion is introduced in this paper. The concept of horizontal bias combustion (HBC) and its principle of reducing NO_x emission are also described. In situ experimental studies were made on the NO_x emission and unburnt carbon loss in a 300 MW lean coal fired boiler, which adopted a new kind of HBC burner with the side secondary air (HBC-SSA) and the horizontally offset secondary air nozzles. Effect of operational parameters, such as the primary air (PA) velocity, the oil secondary air (SA) damper percentage, the SA distribution, the SA horizontally offset angle, the OFA, the PA and coal mixture switching, and the furnace excess air on unburnt carbon in fly ash and the NO_x emission were obtained. Experimental results show that horizontal bias combustion can greatly decrease the emission of NO_x while keeping high combustion efficiency and outstanding flame stability under low load without supporting fuel oil.