@

초록

Ammonia (NH3) co-firing offers a pragmatic pathway for decarbonizing coal-fired power plants; however, the impact of coal rank on the flame structure and emission characteristics in swirl-stabilized combustion environments remains under-investigated. This study evaluated the co-firing characteristics of bituminous and sub-bituminous coals in an 80 kWth pilot-scale down-fired furnace under a constant NH3 injection velocity, which enabled a stable combustion atmosphere even at high co-firing ratios of up to 40%. Internal temperature distributions were corrected using a suction-pyrometer to ensure data integrity and eliminate radiation-induced measurement errors. The results revealed that combustion behaviors and optimal emission control strategies diverged significantly depending on the coal rank. Bituminous coal maintained a stable high-temperature zone (1150–1200 °C) near the burner. Under a 0.9 burner air ratio, it significantly reduced NO levels to 172.7 ppm at a 40% co-firing ratio, which was facilitated by its moderate volatile release and high char-surface reactivity. By contrast, the high-temperature zone for sub-bituminous coal exhibited a downstream shift owing to rapid devolatilization and intensified oxygen competition between NH3 and coal volatiles. For sub-bituminous coal, the optimal burner air ratio (1.0) limited NO emissions to 201.4 ppm at a 40% co-firing ratio. This study demonstrated that stable combustion can be sustained at high substitution rates by controlling the NH3 injection velocity. By providing mechanistic insights and quantitative guidelines for reaction zone control based on coal rank, the findings serve as a fundamental technical basis for developing and designing large-scale NH3 co-firing systems.

키워드