Experimental research on NO emission with coal preheating combustion technology

Coal preheating combustion technology was adopted to achieve stable combustion and low NO emission of Shenmu semicoke, and an air‐staging method was also used to further reduce NO emission. A series of experiments have been launched on a 30‐kW coal preheating combustion test rig with a coaxial jet triple channel nozzle. In the study, coal preheated characteristics, combustion behavior, and the formation and destruction mechanisms of NO were discussed. Shenmu semicoke could be preheated up to a temperature above 840°C, and stable combustion was easily established; ~63% of the volatile and 59% of carbon were released and converted into coal gas in the self‐preheating burner. Flame images along the axis of the down‐fired combustor were gained, and the images was dark red without obvious flame fronts. The initial generation of NO in the near field of the preheated fuel nozzle exit had impacts on the NO emission, and lower initial NO generation might result in lower NO emission. By decreasing the inner secondary gas (air), increasing the external secondary air and adding CO2 in the secondary gas, the initial NO could be inhibited effectively, which finally controlled the NO emission. However, the CO emission might increase in turn generally. In the research, the NOX emissions were