Primary and Secondary Stage Emissions Characterization for Ammonia RRQL Configuration

Ammonia is actively being considered as a carbon-free energy source, however, there are significant challenges with the fuel from an emissions perspective. Rich, Relaxation, Quench, Lean (RRQL) is a staged combustion strategy designed to reduce NOx emissions from ammonia combustion by taking advantage of the reduced NOx levels at equilibrium in rich ammonia combustion and allowing them a considerable residence time to relax to equilibrium levels. Excess ammonia or hydrogen is then burned off in a short lean secondary stage, to prevent fuel slip and minimize second-stage NOx production. A new experimental facility for Rich, Relaxation, Quench, Lean (RRQL) combustion of ammonia-air premixed swirl flames in a 0.7 kW atmospheric burner is characterized by emissions measurements and flame imaging. The facility features a modular swirl burner, a long quartz primary stage, and a quench stage with modular jet injection geometries. This presentation presents emissions characterization of the primary stage to find the optimal equivalence ratio which minimizes NOx production and ammonia slip, and preliminary emissions characterization of the various jet injection geometries in the quenching stage. The basic jet-injection quench geometries have produced sub 50 ppm NOx emissions when using optimal primary and global equivalence ratios.