Six years after revising the new source performance standards (NSPS) for stationary gas and combustion turbines, the EPA is proposing a handful of additional amendments that will, according to the Agency, respond to an industry request to reconsider aspects of the revisions.  The proposal is also intended to recognize the environmental benefit of combined heat and power (CHP) and the beneficial use of low energy content gases.  The proposed rule would not result in additional costs or additional reductions of emissions of criteria pollutants, asserts the Agency.
               Stationary combustion turbines are used to produce electricity and drive heavy equipment such as compressors.  Turbines are located at power plants, pipeline compressor stations, chemical and manufacturing plants, oil fields, landfills, and institutional facilities. 
UARG petition
EPA’s July 2006 NSPS revised the 1979 NSPS for stationary combustion turbines by strengthening the NOx and SO2 standards by 90 percent and 80 percent, respectively, stated the EPA.  The 2006 amendments affected sources for which construction, reconstruction, or modification was commenced after February 18, 2005. 
               Shortly after the NSPS were issued, the Utility Air Regulatory Group (UARG) requested that the EPA reconsider five elements of the final rule, which, according to the UARG, were not included in the proposal for that rule and for which no comments were solicited.  Those elements included the final input and output NSPS for new, modified, and reconstructed large natural gas-fired combustion turbines operating in the simple cycle mode; implications of specifying concentration limits at 15 percent oxygen: and the lack of an identified methodology for calculating compliance for operating periods during which several different standards apply.
Option for heat recovery
The EPA states that the proposed amendments address the issues raised by the UARG as well as other matters.  Specifically, the EPA is proposing to:

• Allow owners/operators of stationary combustion turbines and any associated heat recovery equipment covered by both the previous NSPS (Subpart GG) and a steam generating unit NSPS the option to petition the EPA to instead comply with revised standards for combustion turbines (Subpart KKKK).
• Allow owners/operators of stationary combustion turbines burning by-product gas to petition the EPA for a site-specific NOx limit.
• Specify that even though the definition of “stationary combustion turbine” under CFR Subpart KKKK includes ancillary equipment, only the combustion turbine engine will be considered when determining if a stationary combustion turbine is new or reconstructed.
• Exempt owners/operators of stationary combustion turbines that are complying with the SO2 standard in either of the standards of performance for petroleum refineries from the SO2 standards in Subpart KKKK.
• Exempt owners/operators of stationary combustion turbines that are complying with the SO2 and NOx standards in the municipal solid waste regulations from the SO2 and NOx standards for combustion turbines in Subpart KKKK.
• Amend the SO2 standard for owners/operators of stationary combustion turbines burning low-Btu gases to be the same as the current standard for combustion turbines burning biogas (landfill gas, digester gas, etc.).
• Recognize the environmental benefit of electricity generated by CHP facilities to account for the benefit of on-site generation avoiding losses from the transmission and distribution of the electricity.
• Maintain the current numerical NOx standards but specify that periods of start-up, shutdown, and malfunctions are now covered by the emissions standard.

The EPA is also requesting comment on how to determine when a stationary combustion turbine overhauled off-site is reconstructed.
EPA’s proposed amendments to the NSPS for stationary combustion turbines were published in the August 29, 2012, FR.