Experimental study on combustion and NOx emissions for a down-fired supercritical boiler with multiple-injection multiple-staging technology without overfire air

► Asymmetric combustion and particularly high NOx emissions appearing in down-fired furnaces. ► Applying a deep-air-staging technology especially for these problems in new down-fired furnaces. ► Experimentally evaluating the air distribution effect on coal combustion and NOx emissions. ► Symmetric combustion, high burnout, and relatively low NOx emissions appearing in the furnace.