Characterization of NO emission in combustion of hydrothermally treated antibiotic mycelial residue

• NO emission was studied for combustion of hydrothermal treated (HTT) antibiotic mycelial residue (AMR).
• The AMR fuel has no fixed carbon and contains two types of volatile, light and heavy volatile matters.
• HTT reduces NO emission by 20–30% due to its removal of nitrogen species existing with light volatile.
• Combustion via oxygen staging mainly suppresses the NO formation from nitrogen in heavy volatile.
• It potentially reduces NO emission above 50% by combining HTT and oxygen staging in burning AMR.

The NO emission characteristics from both conventional and air-staged combustions of antibiotic mycelial residue were investigated in the temperature range of 1073–1273 K. The effect of hydrothermal treatment (HTT) prior to combustion on the NO emission was clarified. In conventional combustion, the NO emission from combustion of the hydrothermally pretreated antibiotic mycelial residue (HTT-AMR) was 20–30% lower than that from combustion of the directly dried antibiotic mycelial residue (Dried-AMR). By air-staged combustion, the NO emission of HTT-AMR was reduced by about 45% at 1273 K, compared to that by conventional combustion. As a result, the NO emission was largely reduced by 57% by air-staged combustion of HTT-AMR at 1273 K in comparison with conventional combustion of Dried-AMR, showing a significant combining effect of HTT and air-staged combustion on the NO emission. Results of thermogravimetric analysis and X-ray photoelectron spectroscopy revealed that the AMR based fuels have only volatile matters which consist of light and heavy volatiles. Deconvoluting the NO emission curves demonstrated that the reduction in NO emission via HTT mainly resulted from the removal of the nitrogen in the light volatile as the form(s) of amino acid or/and ammonia, while the reduction via air-staged combustion was because air-staged combustion suppressed the formation of NO from the heavy volatile.