Advancing energy system decarbonization through high-ammonia co-firing: Performance optimization and environmental benefits in representative thermal power generation in South Korea

South Korea has adopted ammonia co-firing in coal-fired power plants to meet its 2030 Nationally Determined Contributions targets for the power sector. This study investigates a 500 MW tangentially fired coal-fired boiler and, for the first time, systematically conducted computational simulations on the transition from ammonia–coal co-firing to pure ammonia combustion in a large-scale coal-fired boiler. This study systematically investigated increased excess air ratio and oxygen-enriched combustion in ammonia co-firing under 50 % ammonia. Based on these findings, a novel optimization strategy, the “Regional Coal Combustion Regulation (RCCR) method,” was developed to achieve stable combustion, enhance the furnace temperature, and significantly reduce NO emissions. NO emissions followed a distinct "increase–decrease–increase" trend as the ammonia ratio increased from 0 % to 50 % (where they peaked), decreased at 75 %, and rose again at 100 %. At 50 % ammonia, the average furnace gas temperature (FGT) decreased by 95.66 K, while NO emissions and unburned carbon (UBC) increased by 251.56 ppm and 4.59 %, respectively. By controlling the coal (char) combustion ratio in the burnout zone to 2.86–12.49 %, the method based on 50 % ammonia, a stoichiometric ratio (SR) of 1.05, and 29 % O2: increased the FGT by 58.52 K and decreased NO emissions and UBC by 133.59 ppm and 4.93 %, respectively, relative to those achieved with 50 % ammonia, an SR of 1.15, and 21 % O2. These findings offer a novel technical approach for optimizing high-ammonia co-firing conditions, facilitating the energy transition of coal-fired power plants and contributing to decarbonization efforts.