Effect of the Adjustable Inner Secondary Air-Flaring Angle of Swirl Burner on Coal-Opposed Combustion

A novel swirl burner with an adjustable inner secondary air (ISA)-flaring angle β is proposed. The authors conducted a combustion experiment in a 0.6 MW wall-fired pilot-scale furnace with the novel swirl burner and numerically simulated the combustion characteristic correspondingly. The effects of the inner secondary air-flaring angle of the burner on coal combustion, including gas temperature, wall temperature distributions, unburned carbon in the fly ash, and NOx emissions, are reported in detail. Both experimental and numerical results indicate that increasing β can improve coal particle ignition and move the flame center close to the burner. To avoid hot corrosion, larger β is recommended, because it helps to lower the temperature level of the furnace wall. The ISA-flaring angle of burner can be optimized to improve burnout and limit NOx emissions. The condition of the highest burnout corresponds to that of the highest NOx emissions with the same ISA-flaring angle of the burner. Combustion efficiency and NOx emissions can be balanced through the variation of β. With this new ISA-flaring angle adjustable burner, coal combustion will become more controllable and cleaner, while being more reliable. © 2015 American Society of Civil Engineers.