Proposed changes to NSPS for gas turbines considered onerous by many users


CTOTF’s™ 38th annual Spring Turbine Users Conference and Trade Show got into the nitty gritty of GT operations and maintenance on the second day of the meeting, conducted at the Marriott Grande Dunes in Myrtle Beach, SC, April 7-11. Day One was devoted to presentations and discussion on training, information resources, and best practices, plus the evening vendor fair.

Tuesday’s program focused on regulatory and compliance issues and GE E-class and legacy engines; the sessions were conducted in parallel. This was the first CTOTF meeting that the Regulatory and Compliance Roundtable, chaired by Scott Takinen, director of executive projects for fossil generation at Arizona Public Service Co, ran an entire day. Judging from the robust content and discussion, it probably could have gone two days without anyone yawning. The morning R&C program addressed environmental regulations, with Vice Chair Kimberly Williams of NV Energy at the front of the room; Vice Chair Alan Bull of NAES Corp, directed the afternoon session on NERC and FERC regulations.

Chairman Pierre Boehler and Vice Chair Ed Wong, both employees of NRG Energy Inc, divided the GE E-class program into two segments: OEM presentations in the morning and presentations by third-party equipment and services providers, plus user-only open discussion, in the afternoon.

That plant managers and supervisors are having a difficult time keeping up with environmental regulations was obvious from the strained facial expressions on many attendees during Williams’ opening presentation, “Proposed Revisions to Combustion Turbine NSPS.” Don’t let the plain-vanilla title fool you. The presentation’s content provided credibility to a message delivered by a user on Monday that went something like this: Don’t be lulled to sleep thinking the federal government is just trying to eliminate coal as an energy source for electric generation; it has declared war on all fossil fuels, and natural gas is next.

Williams eased the group into the subject matter, starting with a history of the New Source Performance Standards for GTs, then providing details of the onerous changes proposed to those regulations, and finally, what impacts EPA’s suggested changes could have on asset owners if enacted as written. It’s fair to say that many of the users participating in the heavily attended session (standing room only) found it difficult to believe what they were hearing.

One example is the proposed change to the definition of “reconstruction,” a trigger for NSPS, which may result in more restrictive operating and compliance requirements. Under the current definition, Williams said, “reconstruction” is taken to mean the replacement of components of an existing facility to the extent that the fixed capital cost of the new components exceeds 50% of the fixed capital cost of a comparable entirely new facility—including major process equipment, instrumentation, auxiliary facilities, buildings and structures, etc.

The new definition, if EPA has its way, would be to use only 50% of the cost of the compressor, combustor, and turbine sections as the “reconstruction” trigger. In EPA think, this typically means that the third time a turbine is overhauled or refurbished it would be considered “reconstructed.” That translates to an NSPS review every 10 years because maintenance costs are cumulative over time.

Curiously, EPA is on the record with the following: “This proposed rule [the proposed revisions in sum] would not result in additional costs or additional reductions of emissions of criteria pollutants.” Another of the agency’s comments: “We do not intend for these editorial revisions to substantively change any of the technical or administrative requirements of the subpart [that portion of Part 60 of Title 40 of the Code of Federal Regulations pertaining to gas turbines] and have concluded that they do not do so.”

If you are not familiar with the foregoing and want to come up to speed in a hurry, access Williams’ presentation in CTOTF’s online Presentations Library. If you don’t know how to do this, see sidebar below. To dig deeper, access the proposed rule and all the comments submitted to EPA.

How to access CTOTF presentations

The user group’s library of presentations is arranged in chronological order by meeting (most recent first). If you don’t already have a “library card” and you are a GT owner or operator, register now at no cost.

Confirmation of your acceptance as a CTOTF member with full IBBCS (Internet Bulletin Board Communications Service) privileges generally will be emailed to you within 72 hours. As a member, access CTOTF IBBCS and sign in. Scroll down the page to “Presentation Library” and click on that link.

Background. Williams, an electrical engineer with 15 years of experience in the environmental aspects of oil production and electric generation, began her presentation by reminding attendees where NSPS fits in the alphabet soup of EPA regulations. Simply put, it establishes pollution control standards of performance for new and modified stationary sources in certain categories—such as electric generating units. These standards are separate from, and in addition to, the Best Available Control Technology/Lowest Achievable Emission Rate limits associated with Prevention of Significant Deterioration/New Source Review rules.

NSPS for gas turbines date back to 1979, Williams said, when the standards were presented in 40 CFR 60 Subpart GG and made effective on Oct 3, 1977. More restrictive standards were issued in July 2006 and published in 40 CFR 60 Subpart KKKK—so-called Quad K. The Utility Air Regulatory Group (UARG), a voluntary, not-for-profit group of electric utilities, other electric generating companies, and national trade associations, filed petition for reconsideration in September 2006. EPA’s proposed revision was published on Aug 29, 2012. This version has not been promulgated—yet. Williams did not discuss the possibility of ongoing appeals and the degree of success they may or may not have, or when the proposed rules could become law.

The Quad K standards in effect today apply to stationary gas turbines that commenced construction, modification, or reconstruction after Feb 18, 2005. EPA’s proposed changes to those rules include the following, among many others:

• Modify the test for “reconstruction” as described earlier.

• Include startup and shutdown activities in emissions standards. Today’s NOx limits do not apply to engine starts and stops, or to engine malfunctions. Williams said that EPA is considering designating the first 30 minutes of operation as “part load,” subject to a higher NOx limit. She suggested that this would complicate monitoring.

• More restrictive NOx averaging periods, now 30 days for gas turbines in combined cycles with a peak-load heat input greater than 850 million Btu/hr (HHV), and four hours (rolling average) for simple-cycle GTs with a peak-load heat input equal to or less than 50 million Btu/hr (HHV). Note that the first example is for a 2008-vintage GE 7FA, the second for a P&W SwiftPac® built in 2008.

To illustrate the level of detail associated with some of proposed changes, consider that the 30-day average for large frame engines in combined cycles would be acceptable for any unit using the output-based standard (see next bullet). However, those using the input-based standard would have to comply with a four-hour average. Proposed changes to the NOx averaging period for simple-cycle turbines is far more complex.

• Change the output-based NOx standard from gross to net basis with units of lb/MWh.

• Add a new form of input-based NOx standard with units of lb/million Btu.

• New compliance monitoring requirements. Example: Units using post-combustion NOx controls to comply with emissions rules can no longer rely on Part 75 CEMS (Continuous Emission Monitoring System) because the specified analyzer span is inconsistent with Part 75.

• New definition for turbine tuning, which would be limited to 30 hours annually: As proposed it means planned maintenance of a lean, premix combustion system involving adjustment of the operating configuration to maintain proper combustion dynamics.



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