Selective Catalytic Reduction (SCR)

Under the presence of a catalyst and at a reaction temperature of 300-450°C, ammonia (NH₃) or hydrocarbons react with NO or NO₂ to generate N₂ and H₂O. The denitrification efficiency exceeds 90%.

Main reducing agents: liquid ammonia, urea, and ammonia water. Trend: replacing liquid ammonia with urea.

Characteristics of SCR systems:

• Relatively complex in structure but convenient to operate;
• Few moving parts, resulting in high reliability;
• No by-products, but consumes catalyst;
• High denitrification efficiency, over 90%;
• High investment cost under special circumstances, such as:
• Low-temperature catalysts (150-280°C)
• High-temperature catalysts (≥450°C)
• Sulfur-resistant catalysts
• Wear-resistant catalysts