Potential and assessment of urea-based SNCR in a small-scale multi-fuel biomass furnace (POSTER)

The aim of this work is to assess the potential NOx reduction achieved with urea-based SNCR in a small-scale biomass grate furnace operated with forest biomass residues. This 70-kW moving grate furnace offers several flexible primary NOx reduction measures, such as single or double air staging and flue gas recirculation (FGR), which were presented in our latest work. Experiments were performed to test the main parameters of SNCR efficiency, namely the urea amount (normalised stoichiometric ratio), temperature and residence time, and the results were compared with those of a kinetic simulation applying ideal reactors in conjunction with a detailed nitrogen chemistry mechanism from literature.
The experimental and simulation results show an optimum temperature of around 950 °C, enabling a NOx reduction of over 90% in this biomass furnace. However, the NOx reduction was limited to 60–70% due to the legal limits for NH3 emissions. At lower temperatures or residence times, a significant increase in NH3 emissions was observed. The optimum operating point for achieving 60–70% NOx reduction and for complying with the NH3 legal limits shows great potential for using SNCR in small-scale biomass furnaces, if the required temperature and residence time can be provided.