Selective catalytic reduction | 39’-11” Combination SCR/CO catalyst SCR catalyst CO catalyst AIG


Conventional SCR stack to inlet flange. Length: 39’ 11”


35’-5”


Tempering air system ~30% of exhaust 2 x 100% fans


Exhaust stack


GT Up to 1200°F < 900°F


T = 300°F at AIG P = +30 in wg


Instrument air Ammonia FCV


Direct Injection SCR stack to inlet flange. Length: 35’ 5”


Figure 8. Comparing the footprint of a conventional LM6000 SCR (top) to that of EnergyLink’s original LM6000 Direct Injection test rig (bottom). Source: EnergyLink International


large SCR duct and exhaust stack are installed in less than a day on both conventional SCR and DI units, using quick-bolt connections. However, installing a conventional SCR requires additional time for the AIG and AVS, adding a week or more to the schedule. With DI, installation is significantly faster.


Direct Injection SCR saves roughly 20% in life-cycle costs.


● Precise, adjustable injection. One of the key features of EnergyLink’s Direct Injection system is its ability to inject liquid ammonia at multiple locations and various radial distances within the highly turbulent circular inlet (or Direct Injection duct). This strategy helps achieve NOx


and CO reductions comparable


to or better than those of a conventional SCR system. EnergyLink’s Direct Injection system replaces the ammonia injection grid and its many valves and control devices with a simplified setup consisting of injection lances and custom-designed nozzles. These nozzles keep the ammonia in liquid form for proper atomisation and are easily adjustable in depth


AIG exterior


Ammonia storage tank 19% aqueous ammonia


Ammonia vaporiser


Ammonia transfer pumps


2 x 100% pumps Electric


air heaters 3 x 50%


Heated air to vaporiser T = 700 to 800°F at AIG P = +45 to +50 in wg


Dilution air blowers 2 x 100% blowers


Figure 9. Process flow diagram of conventional aqueous ammonia SCR, with green boxes and yellow highlights showing the components not required for a Direct Injection SCR system. Source: Dan Ott, Environex, Inc.


● Reduction in parasitic loads, increase in net power. Eliminating ammonia vaporisation fans and heaters reduces parasitic loads and lowers operating and maintenance costs. Each gas turbine in operation, whether for baseload or peaking needs, will save money, especially since many datacentres and peaking plants operate multiple units. For a single LM6000 gas turbine, a 20-horsepower (14.9 kW) reduction in system power use, combined with conservative per kWh costs of 10 cents (for baseload power at 100% capacity factor) and 20 cents (for peaking power at roughly 17% capacity factor), results in annual savings of over €11 000 (US$13 000) and €3900 ($4500), respectively. When these savings are multiplied across a fleet of units, the total savings quickly add up.


and position to ensure an even distribution of ammonia and a low percentage (%RMS) ammonia-to-NOx


variance at the catalyst. AIG interior


Figure 11. Conventional ammonia vaporisation skid (AVS)


Figure 10. Conventional ammonia injection grid (AIG). 22 | May/June 2026 | www.modernpowersystems.com


● Return on investment. We believe that the future of SCR technology for simple- cycle gas turbines is Direct Injection, as indicated by recent orders from power and datacentre customers. In the words of Paul DiMascio, chief engineer at ProEnergy Services and client sponsor of EnergyLink’s Direct Injection demonstration project: “I sincerely hope new plants adopt this technology because it reduces capital expense a lot and reduces operating expenses too. That lowers the cost of electricity and helps everyone,” said DiMascio. “The smaller footprint reduces foundation costs and makes the entire plant smaller, so you need less acreage for it. Direct Injection will also reduce maintenance costs because the ammonia injection system (an immense AIG in the case of conventional SCR) gets markedly smaller and cheaper to maintain. As plants with existing AIGs age, the maintenance costs increase, and there will come a time when you can install a much smaller injection system close to the turbine, eliminate an expensive skid, and get a good return on your investment.”


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