Numerical modelling of ammonia-coal co-firing in a pilot-scale fluidized bed reactor: Influence of ammonia addition for emissions control

• A 2D Eulerian-Lagrangian model describing the coal-NH 3 co-firing is developed. • The numerical model is validated against experimental data on coal combustion. • The NH 3 ratio effect on heat release, and carbon, NO and NH 3 emissions is studied. • The effect of NH 3 injection position and air staging on NO formation is evaluated. • The feasibility of co-firing coal and NH 3 in a fluidized bed reactor is assessed. The co-firing of coal and NH 3 is a sustainable solution allowing the retrofitting of coal power facilities without major modifications while contributing to global decarbonization goals. However, the use of NH 3 for power generation still presents some research gaps. This study delivers a 2D Eulerian-Lagrangian numerical model describing the co-firing of coal-NH 3 in a pilot-scale fluidized bed reactor. The numerical model is validated against experimental data on coal combustion to assess the accuracy of the model·NH 3 co-firing ratio is varied between 0 and 80% (by mass) and the effect on the combustion process is broadly investigated to determine the impact on heat release, and carbon, NO, and NH 3 emissions. The effect of NH 3 injection position into the reactor and air staging on NO formation is studied. Also, the impact of NH 3 on the reactor temperature distribution and radiative flux is evaluated. Results indicate that NH 3 co-firing delivers CO 2 emissions decrease of up to 26% compared to pure coal firing. For a co-firing fraction of 10% NH 3 , NO emissions level was identical to that of coal firing alone, yet between 20 and 80% ratio NO emissions gradually decreased by up to 40%. The NH 3 injection location had a substantial effect on NO emissions, with injection points further downstream the bed surface leading to increased NO concentrations. Air staging also proved to have a dominant effect on NO formation, with a 50% reduction of NO emissions obtained for a 20% air staging alone. Lower gas temperatures and decreased radiative flux were predicted as the NH 3 ratio increased. Given the similar heat transfer rates measured between 10 and 20%, a 20% NH 3 operation would be possible without a detrimental effect on temperature and radiative flux.