Highly efficient combustion with low excess air in a modern energy-from-waste (EfW) plant

Highlights: • Operation of a commercial EfW plant with low excess air. • Uncontrolled NOx emissions are considerably reduced by lowering O₂ in the combustion process. • Stable combustion control avoids CO formation even at O₂ concentrations below 3 vol%. • High adiabatic combustion temperatures do not increase the amount of uncontrolled NOx. - Abstract: 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 (λ < 1.2) while keeping CO and NOx at levels well below the legal emission limits.