REVEALING HETEROGENEITY OF N2O CONCENTRATION IN SELECTIVE CATALYTIC REDUCTION DENITRIFICATION: A MULTI-POINT SAMPLING STUDY IN COAL-FIRED POWER PLANT

Selective catalytic reduction (SCR) plays a critical role in achieving ultra-low emissions from coal-fired power plants by enabling highly efficient removal of nitrogen oxides (NOx). However, the denitrification process may concurrently generate nitrous oxide (N 2 O), a potent greenhouse gas often overlooked in emission control strategies. Crucially, conventional continuous emission monitoring systems (CEMS) focus solely on NOx reduction efficiency without tracking byproduct formation, creating a potential blind spot for N 2 O emissions when reduction reactions are incomplete. To address this gap, this study conducted multi-point on-site sampling monitoring within SCR system of ultra-low emission units at a 693 MW coal-fired power plant and a separate 2× 300 MW plant. A pivotal question was investigated: Are N 2 O emissions inevitably elevated by SCR operation? Our findings reveal significant spatial heterogeneity in N 2 O distribution: while concentrations increased at certain locations (e.g., upstream catalyst layers), they unexpectedly decreased at others (e.g., optimized mid-reactor zones), demonstrating position-dependent synergistic reduction of NOx and N 2 O under specific operational conditions. This work highlights the necessity of multi-dimensional emission assessment beyond standard CEMS protocols and provides actionable insights for co-controlling air pollutants and greenhouse gases in industrial air pollution control systems.