Investigation of NO-Formation in Humid, Ammonia-Doped Combustion

Decarbonizing the energy sector promotes the utilization of renewable fuel sources like Syngas from biomass. Syngas typically comprises small quantities of fuel-bound nitrogen (FBN) like ammonia which is associated with high NO-emissions when combusted in a customary gas turbine system. In atmospheric combustion experiments conducted at TU Berlin, small quantities of ammonia were added to both natural gas and a surrogate Syngas representing Syngas derived from biomass. This results in an ammonia-to-NO conversion rate of around over 70%, which decreases with increasing ammonia concentration. A difference in conversion rate between surrogate Syngas and natural gas is particularly noticeable at lower ammonia concentrations, which diminishes as concentration increases. The experimental combustion process is validated with a Chemical Reactor Network (CRN) using Cantera, which captures the emission behaviour observed in the experiment well. The chemical reactor representing the flame is additionally modeled as a 1D-flame in Cantera, providing the input for an in-depth investigation of the flame kinetics with a sub-mechanism accounting and reaction tracing algorithm (SMART) to investigate the NO-formation. NO is primarily generated within the flame zone predominantly through the fuel pathway, although production is diminished by the DeNOx pathway. Finally, NO-formation is investigated for varying combustor diameter. NO-emissions decrease with increasing diameter of the combustion chamber. SMART analysis shows that with increasing the combustor’s diameter, the increase in NO depletion via the DeNOx pathway surpasses that of production via the Fuel NO pathway. Consequently, this results in a slight reduction in the overall NO output, which could arise from increased heat loss with increased diameter.