Influence of NOx in combustion of biomass fuel

Utilisation of biomass in combustion technologies alleviates several pollution-related environmental impacts. This process often occurs in thermally reactive conditions. The present study highlights the cogent influence of nitrogen oxides (NOx) in combustion of biomass (surrogate) fuel. At practical industrial fuel-rich condition, we investigated the thermal decomposition of biomass surrogate (morpholine) with oxides of NOx. A laboratory-scale tubular laminar-flow reactor enabled the flexible optimisation of reaction parameters within the temperature range of 300 °C to 1100 °C at different He-O2-NOx reactive mixtures, with Fourier transform infrared (FTIR) spectroscopy, NOx chemiluminescence and gas chromatography (μGC) serving to assess the major gas products as well as N-conversion profiles. The results offer two important remarks; (i) the presence of NOx lowers the ignition temperature of the morpholine as a result of initial nitration processes, formulating insights towards the safety implications in a typical biomass operating plants; (ii) at elevated temperature above 800 °C, morpholine converts NOx at approximately 80 % reduction efficiency, depending on oxygen abundancy of the system. These findings shed light on biomass-NOx interactions occurring in various industrial processes, such as in thermal firing of solid biomass fuels, and particularly, in fuel stagging technology utilising biomass as the major reburn fuel.