Influence of different outer secondary air vane angles on flow and combustion characteristics and NO_x emissions of a new swirl coal burner

Measurements were taken for a 300 MW_e wall-fired pulverized-coal utility boiler installed with eight centrally fuel rich swirl coal combustion burners in the bottom row of the furnace during experiments. For various outer secondary air vane angle settings, flow characteristics, gas temperature and gas species concentrations in the burner region were measured. The results show that with decreasing outer secondary air vane angle, the swirl intensity of air, divergence angles and maximum length and diameter of the central recirculation zone all increased; the turbulence intensity of the jet flow first increased and then quickly decreased. With decreasing outer secondary air vane angle, the rate of increase in the gas temperature in the early stage and the rate of decrease in the later stage increased along the jet flow direction. For outer secondary air vane angle of 25°, the O₂ concentration along the jet flow direction in the burner region was low, and the CO concentration decreased with increasing outer secondary air vane angle. For outer secondary air vane angles of 30° and 35°, the NO_x concentrations were less than those for 25° and 40° outer secondary air vane angles. Gas species concentrations in the side wall region varied slightly with a change in the outer secondary air vane angle.