The effect of low excess air and high adiabatic combustion temperatures on CO and NOx formation has been investigated on a commercially operated energy-from-waste plant. With optimal combination of low O2 levels and stable combustion control, uncontrolled NOx levels could be lowered to 100–150 mg/Nm3 (dry, at 11% O2) while keeping CO emissions at low levels. Even at adiabatic temperatures above 1400 C thermal NOx hardly contributed to the total NOx emissions in a grate-fired EfW plant. An advanced combustion control system allowed continuous operation with very little excess air (k < 1.2) while keeping CO and NOx at levels well below the legal emission limits.
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