Numerical modelling of the coal phase-out through ammonia and biomass co-firing in a pilot-scale fluidized bed reactor

The co-firing of ammonia (NH₃) with coal has raised awareness, boosting NH₃ research and development on its use and deployment as a sustainable fuel. Recent advancements point towards the co-firing of coal with biomass and NH₃ as a state-of-art strategy to phase-out coal from coal-based power stations. The implementation of NH₃ to the coal-biomass fuel mix allows not only to decarbonize coal-fired processes but also reduces biomass exploration costs to avoid feedstock availability disruption while increasing the power station production efficiency. Moreover, such a strategy brings an alternative player into the environmentally friendly power mix portfolio, accelerating the coal phase-out from electricity production. However, the use of NH₃ for power generation still presents some research gaps. Thus, this study delivers a 2D Eulerian-Lagrangian numerical model to describe the co-firing of coal with biomass and NH₃ in a pilot-scale fluidized bed reactor. The numerical model is validated against experimental data on coal and biomass combustion to assess the model's accuracy. The coal, biomass, and NH₃ co-firing ratios are varied to the point where coal is gradually reduced from the fuel mix, and its effect on the combustion processes is broadly investigated to determine the biomass and NH₃ impact on the reactor's emissions. Overall, the use of both biomass and NH₃ showed to broadly reduce carbon and NO emissions from coal-fired energy systems, emphasizing the potential addressed to biomass as an alternative to coal and NH₃ as an effective carbon-neutral fuel of the future.