Despite its advantages, SCR also faces several challenges:
Ammonia Slip: Excess ammonia can slip through the system unreacted, leading to secondary pollution. Catalyst Deactivation: Over time, catalysts can lose their activity due to fouling, poisoning, or thermal degradation. Operating Costs: The need for continuous supply of reductants like ammonia or urea can add to operational costs. Space Requirements: SCR systems can be bulky, making them challenging to implement in space-constrained applications.
