Eliminating pollutant emission is a lofty goal for an industrial facility. Discover how to minimize NOx emission in gas turbines specifically by reading our explanation of the various processes utilized. You can even learn the optimal setup for maximum NOx cutback.
Water or Steam Injection
Introducing water or steam into a combustor is also referred to as wet control. Each lowers the flame temperature of combustion reactions, which leads to nitrogen oxide (NOx) production and in turn limits the output of NOx. Wet control methods date back to the late 1970s when gas turbine regulations like the Clean Air Act of 1977 were enforced. Water or steam is introduced according to a specific water-to-fuel ratio, which depends on the fuel used, to maximize cooling while making sure reactions still proceed as they should. One limitation of this method is that carbon monoxide (CO) and hydrocarbons release when wet controls are introduced. Each are dangerous chemicals for humans and considered pollutants.
Dry Low Emission (DLE)
An alternative to using water or steam was developed so that peak flame temperature could decrease. This approach to minimizing NOx emissions in gas turbines adjusts several combustion conditions, and it is called Dry Low Emission. These modifications include using lean combustion conditions, staging multiple combustions, and using a catalyst for combustion. Lean combustion lowers the flame temperature by allowing a high air-to-fuel ratio. Staged combustion techniques create a two-part sequence that neutralizes existing NOx and other harmful substances in a secondary combustion area. Catalytic methods provide a way for the combustion to occur completely without a flame. These various interventions all lower the output of NOx.
Selective Catalytic Reduction (SCR)
Selective Catalytic Reduction was developed in the 1980s to address NOx formation after its creation to drive down the presence of NOx even further than DLE methods alone allow. In a SCR-equipped gas turbine, an ammonia reagent reacts with gas containing NOx to convert it into harmless nitrogen and water vapor gases. When combined with DLE strategies, nitrogen oxide emission significantly lowers.
If you’re interested in incorporating SCR systems for your gas turbines, contact our SVI Dynamics’ team for further information about our SCR systems and their implementation.