Numerical Investigation of Rich-Lean Staging in a SGT-750 Scaled Dry Low Emission Burner With Partially Decomposed Ammonia

Ammonia is emerging as a very convenient hydrogen- and energy-carrier in the context of present efforts to curb carbon emissions from the power-generation and transport sectors. As opposed to hydrogen, the properties of ammonia make it significantly simpler to transport and store. Early exploratory work on the combustion of pure ammonia in laboratory-scale gas turbine combustors revealed that the adoption of a longitudinal rich-lean staging strategy in the operation of the device is a convenient approach to minimize NO_x and N₂O emissions from fuel-bound nitrogen oxidation. Moreover, recent experimental evidence acquired at SINTEF confirms that the low-emission performance achieved with rich-lean staging also applies to the combustion of partially decomposed ammonia. In this paper, we report a comprehensive numerical modeling study that exploits large eddy simulation (LES) in conjunction with detailed chemical kinetics and a chemical reactors network (CRN) model to assess a rich-lean staging strategy applied to the combustion of partially decomposed ammonia in the Siemens Energy fourth-generation dry low emission (DLE) burner. Data analysis performed from both numerical modeling approaches, LES and CRN, confirm that the rich-lean staging strategy tested in the present study indeed results in significantly lower emissions compared to the conventional operational profile of the burner. Furthermore, reaction pathways analysis performed on the CRN data reveals important details that characterize the different evolution of nitrogen species between the nonstaged and staged operation of the burner, ultimately leading to the observed difference in NO_x and N₂O emissions