AN EXPERIMENTAL INVESTIGATION INTO AMMONIA COMBUSTION AND NOx EMISSION IN A FLUIDIZED-BED REACTOR

Ammonia (NH₃) combustion and NOx emission in a fluidized-bed reactor with quartz particles (size fraction 295 μm-354 μm) as the bed material has been experimentally studied over a range of furnace set temperatures (900 K-1300 K), equivalence ratios (ɸ = 0.6, 0.7, 0.8, 0.9, 1.0, 1.1), and fluidization numbers (1, 3, 5, 7, 9). NH₃ oxidation commenced at ~ 900 K and complete NH₃ conversion was achieved at 1250 K-1300 K. Greater NH3 conversion was generally achieved at lower equivalence ratios. IIncreasing fluidization number led to more sharply increasing NH3 conversion with increasing furnace set temperature, as well as complete NH3 consumption at lower furnace set temperatures. The measured axial temperature profiles of the reactor indicated that increasing fluidization number resulted in the combustion moving from the bed surface into and through the emulsion phase towards the distributor of the fluidized-bed. Under all experimental conditions tested, NO emission was negligible at furnace set temperatures < 1250 K, experienced a maximum at 1250 K, and declined thereafter with increasing furnace set temperature. Increasingly fuel-lean conditions resulted in increasing NO emission, while fuel-rich conditions returned far lower or negligible NO concentrations. Experiments conducted at higher fluidization numbers resulted in increasing NO emissions compared to those conducted at lower fluidization numbers. Overall, fluidized-bed NH3 combustion is a new and innovative concept which has been identified as a technology that may be suitable for carbon-free large-scale power generation applications. The present study reports original work that facilitates future research which may be aimed at investigating the influence of fluidization regime, particle size, type of bed material, flame behavior, fuel handing, fuel injection, etc., while also being able to assist in engineering scale-up and industrial design of a fluidized-bed NH3 combustor.