Abstract: Nitrogen oxides (NOx) are major air pollutants that cause acid rain, photochemical smog and exacerbate the greenhouse effect, making their emission control a key focus in the environmental protection field. As China’s environmental standards become increasingly stringent and the petrochemical industry continues to develop, higher requirements have been placed on pollutant emissions from petrochemical enterprises, particularly ethylene plants. Currently, the industry widely adopts the combined technical approach of "Low-NOx burners + selective catalytic reduction (SCR) denitrification systems" to control NOx emissions in flue gas. To meet the stringent NOx emission standards and ensure efficient and stable operation of denitrification systems in ethylene plants utilizing "low-NOx burners + SCR" technology, this paper analyzes common operational anomalies such as excessive NOx emissions and ammonia slip, and proposes optimization measures, aiming to provide valuable insights for fault diagnosis and cost-effective operation of denitrification systems.

Key words: denitrification system (Selective Catalytic Reduction, SCR), nitrogen oxides (NOx), catalyst