Stationary Gas and Combustion Turbines: New Source Performance Standards (NSPS)

Rule Summary

Stationary combustion turbines are a type of internal combustion engine that is composed of three main sections. The first section, the compressor, draws air into the engine, pressurizes it, and feeds it to the combustion chamber. Fuel is mixed with the compressed air and the mixture is burned in the combustion chamber. The combustion produces a high temperature, high pressure gas stream that enters and expands through the final section, the turbine section. As hot combustion gas expands through the turbine section, it spins rotating blades which turn a shaft. The rotating blades both drive the compressor to draw more pressurized air into the combustion section and either spin a generator to produce electricity or a mechanical drive (e.g., a compressor).

The turbine exhaust gases are hot enough, several hundred degrees, to produce additional useful output. Combined cycle and combined heat and power units use heat recovery steam generators (HRSG) to produce steam from the thermal energy in the turbine exhaust. This steam can either be used to produce additional electricity or for direct heating applications.

The New Source Performance Standards (NSPS) for stationary combustion turbines are outlined in the Code of Federal Regulations under 40 CFR Part 60 Subparts GG and KKKK. Subpart GG covers turbine engines that commenced constructed after October 3, 1977 and before February 18, 2005. Subpart KKKK covers both the combustion turbine engine and any associated heat recovery steam generator for units that commenced construction after February 18, 2005. The key pollutants EPA regulates from these sources includes nitrogen oxides (NOx) and sulfur dioxide (SO₂).

On November 22, 2024, the EPA proposed to strengthen limits on emissions of nitrogen oxides (NOx) from most new, modified, and reconstructed fossil fuel-fired stationary combustion turbines, reducing dangerous air pollution for nearby communities. The proposed New Source Performance Standards (NSPS) are based on the application of combustion controls and selective catalytic reduction (SCR), a cost-reasonable and widely used add-on control technology that limits emissions of NOx. In addition, EPA is proposing to maintain the current limits for sulfur dioxide (SO2), which is well-controlled in this sector based on the long-term required use of low-sulfur natural gas and distillate fuels.