Combustion characteristics of fuel flexibility with coal–biomass–ammonia co-firing in a circulating fluidized bed system

Biomass and ammonia are promising resources for reducing greenhouse gas (GHG) emissions from coal-fired power plants. Some of these plants are co-firing biomass with coal. This study examines coal–biomass–ammonia co-firing in a circulating fluidized bed system, focusing on temperature and pressure profiles in the combustor, pollutant emissions, and combustion efficiencies. GHG emissions, specifically CO₂ and N₂O, were compared based on biomass ratio (8 % lower and 23 % higher) and the ammonia supply position in the dense bed zone (DBZ) and wind box (WB). When ammonia was supplied to the DBZ at a lower biomass co-firing ratio, CO emissions increased to 213.4 ppm due to the competition between coal and ammonia combustion. In contrast, ammonia supplied to the WB at a higher biomass ratio (22–23 % as a thermal base) resulted in the lowest CO emissions at 6.6 ppm, reducing heat losses. The N₂O concentration from higher biomass co-firing with NH₃ and coal when injected at WB was lower than that from a lower biomass ratio (8 % as a thermal base). This study highlights the potential of coal–biomass–ammonia co-firing to reduce GHG emissions while maintaining combustion efficiency, with minimal CO impact, offering a sustainable solution for bioenergy generation in coal-fired power plants.