Exam Question
(a) How does the Selective Catalytic Reduction (SCR) system work? (10)
(b) If Selective Catalytic Reduction (SCR) has such an extremely high NOx reduction efficiency why is it so rare in marine applications? (10)
Class 4 (4th Engineer)
SSEP
📅 Apr 2025
Reference Answer
### (a) How does the Selective Catalytic Reduction (SCR) system work?
Selective Catalytic Reduction (SCR) is an advanced post-combustion exhaust gas treatment technology designed to significantly reduce nitrogen oxides (NOx) emissions from internal combustion engines by converting them into harmless diatomic nitrogen (N₂) and water (H₂O).
**1. Fundamental Principle (Selective Catalytic Reduction):**
* The core principle involves the injection of a liquid reducing agent (typically urea or ammonia) into the exhaust gas stream upstream of a catalyst bed.
Selective Catalytic Reduction (SCR) is an advanced post-combustion exhaust gas treatment technology designed to significantly reduce nitrogen oxides (NOx) emissions from internal combustion engines by converting them into harmless diatomic nitrogen (N₂) and water (H₂O).
**1. Fundamental Principle (Selective Catalytic Reduction):**
* The core principle involves the injection of a liquid reducing agent (typically urea or ammonia) into the exhaust gas stream upstream of a catalyst bed.
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