Ammonia Injection Grid (AIG) Tuning

Well-tuned Ammonia Injection Grids Optimize SCR System Performance
Plot of non-uniform Ammonia Distribution over an SCR Catalyst, Resulting in Low NOx Conversion and High Ammonia Use was solved with Ammonia Injection Grid Tuning

SCR catalyst systems are designed to operate within tight tolerances for the distribution of ammonia to NOx at the inlet to the SCR catalyst. Operation outside of the prescribed tolerances for ammonia distribution can increase ammonia slip and NOx emissions, increase ammonia consumption and reduce the life of your catalyst. Ammonia Injection Grid Tuning with Environex can help you

  • Reduce ammonia slip,
  • Reduce stack NOx emissions,
  • Reduce ammonia consumption, and ultimately
  • Prolong the lifespan of your SCR catalyst

Poor ammonia-to-NOx distribution can be the result of flaws in the system design, changes in plant operating profile, plugging of AIG nozzles or other system maintenance issues, changes in combustion dynamics, or the gradual degradation of SCR system performance over time.

AIG Tuning with Environex has reduced combined stack NOx and ammonia slip emissions as much as 45%.

AIG tuning restores the ammonia-to-NOx distribution at the SCR catalyst inlet to levels within the specified tolerances. This is achieved by balancing the flow through the ammonia header valves to carefully match the ammonia distribution to the SCR inlet NOx profile. Environex has a proven track record of successfully tuning ammonia injection grids to reduce ammonia slip and ammonia consumption. Recent power industry AIG tuning projects have yielded reductions in combined stack NOx and ammonia slip emissions of 20-45%.

Ammonia Injection Grid tuning should be performed upon commissioning, after SCR catalyst replacement, when there are any major changes to your plant’s operating profile, after any upgrades or changes to the plant combustion dynamics, or after any catastrophic HRSG events. The AIG tuning process is also effective in identifying bypass locations around the catalyst and catalyst “dead spots”.