Views: 0 Author: QT Publish Time: 2025-08-12 Origin: QT
If your Selective Catalytic Reduction (SCR) system isn't performing as it should, you might be quick to blame “bad catalyst quality.”
But in reality, premature SCR catalyst failure is rarely the result of a single flaw. In most industrial cases—whether in refinery applications, power plants, or heavy-duty diesel systems—multiple degradation mechanisms act together.
Below, we break down five often-overlooked root causes of catalyst deactivation, with insights drawn from real industrial cases and peer-reviewed studies.
When your SCR unit operates at high temperatures (often above 650°C), the crystalline structure of many zeolites begins to collapse, reducing surface area and active sites.
According to Gao et al., Applied Catalysis B: Environmental (2013), even small variations in operating temperature can accelerate this process.
Tip: Operating within the catalyst's designed temperature window is essential. CHA-type zeolites (e.g., SSZ-13) have shown superior stability under severe hydrothermal conditions compared to ZSM-5.
Certain flue gas components—especially sulfur oxides (SOx) and alkali metals—can irreversibly deactivate the active metal sites in your catalyst.
A study by Qi et al., Catalysis Today (2020) shows that sulfur poisoning is particularly severe in Cu-based SCR catalysts.
Tip: Incorporate upstream gas pretreatment, and schedule periodic chemical cleaning. When possible, opt for zeolites with tighter pore structures to reduce contaminant diffusion.
Dust, ash, or catalyst fines from upstream processes can clog the pore network, lowering conversion efficiency.
Real-world plant audits (e.g., IEA Clean Coal Centre Report, 2019) suggest that blockage often goes undetected until performance drops significantly.
Tip: Install adequate filtration before the SCR reactor, and monitor differential pressure across the catalyst bed.
Even the best catalyst will underperform if the ammonia injection strategy is poorly tuned. Low ratios result in incomplete NOx reduction, while excessive ammonia leads to slip and secondary reactions.
Tip: Calibrate ammonia injection using online sensors, and adjust based on seasonal or load changes.
It may sound simple, but improper handling during loading/unloading can cause cracks, breakage, and loss of active material.
Tip: Train staff in proper handling procedures and consider pre-shaped catalyst blocks to minimize breakage.
While the above issues are mostly operational, your choice of catalyst material can influence resistance to these factors.
CHA-type zeolites, such as SSZ-13, have demonstrated:
High hydrothermal stability up to 800°C
Strong resistance to SOx poisoning
Excellent NOx conversion at low temperatures
These advantages won’t eliminate operational issues, but they can extend catalyst service life when paired with proper system maintenance.
Gao, F., et al. "Cu-SSZ-13 – A highly active low-temperature NH3-SCR catalyst." Applied Catalysis B: Environmental, 107(3–4), 2011, pp. 120–129.
Qi, G., et al. "Impact of SO₂ on Cu/SSZ-13 SCR catalysts." Catalysis Today, 320, 2020, pp. 25–33.
International Energy Agency (IEA) Clean Coal Centre. SCR Catalyst Management in Power Plants, 2019.
Q1: How can I tell if my catalyst is suffering from hydrothermal aging?
Look for a gradual drop in NOx conversion despite stable upstream conditions, and confirm via surface area or crystallinity measurements.
Q2: Is SSZ-13 always the best choice for SCR?
Not always—it excels in certain conditions (high temp, high moisture), but selection should be based on your flue gas composition and operating profile.
Q3: Can operational fixes restore a poisoned catalyst?
Sulfur poisoning is often irreversible, but proper regeneration can sometimes recover partial activity.
Q4: How often should I replace an SCR catalyst?
Industrial practice ranges from 3–7 years, depending on load, fuel type, and maintenance quality.
