The Florida Department of Environmental Protection on May 1 granted Duke Energy Florida a final air permit revision that extends the federal Mercury and Air Toxics Standards (MATS) deadline for the coal-fired Crystal River Unit 4 and 5 to April 16 of next year for mercury emissions only.
Said the revised permit: “For Units 4 and 5, from April 16, 2015, to April 15, 2016, compliance with the mercury MATS emissions standard of 1.2 lb/TBtu or 0.013 lb/GWh in 40 CFR 63, Subpart UUUUU, Table 2, shall be demonstrated as a one-year block average, rather than as a 30-day, or 90-day, average. For mercury, the MATS compliance date given in 40 CFR 63.9984(b), and referenced in subsequent sections of Subpart UUUUU, is extended to April 16, 2016. For all other MATS-related requirements for Units 4 and 5, the compliance date remains April 16, 2015.”
Duke Energy Florida, a subsidiary of Duke Energy (NYSE: DUK), told the department that it needed the extension because it suddenly last year began running into unusually high mercury emissions at these two units, and that it needed the extra time to install technology to fix the problem.
Emissions units 003 and 004 (Unit 5 and Unit 4, respectively) are fossil fuel-fired steam generators, each consisting of a pulverized coal, dry bottom, wall-fired boiler rated at 760 MW. Air pollution control equipment includes: low-NOX burners; selective catalytic reduction (SCR) systems; flue gas desulfurization (FGD) systems; acid mist mitigation (AMM) systems; and, an electrostatic precipitator (ESP) manufactured by Combustion Engineering. Units 4 and 5 share a common 550-foot-tall chimney with separate internal stack liners with continuous emissions monitoring systems (CEMS) on each stack liner.
The delay does not impact the coal-fired Units 1 and 2 at Crystal River (Unit 3 is a retired nuclear facility). But the revised permit does contain a provision that the utility added to it previously, namely: “Units 1 and 2 shall cease to be operated as coal-fired units by December 31, 2020.”
- Emissions unit 001 (Unit 1) is a pulverized coal, dry bottom, tangentially-fired boiler. It is rated at 440.5 MW.
- Emissions unit 002 (Unit 2) is a pulverized coal, dry bottom, tangentially-fired boiler. It is rated at 523.8 MW.
Said the utility in its Jan. 13 application for the MATS extension for Units 4 and 5: “Based on recent monitoring and testing as described previously in a letter to DEP and summarized in this report, DEF is submitting a Title V air operation permit revision application to install and operate additional mercury emission control systems for Units 4 and 5. Due to the lead time needed for the design, installation and operational tuning, DEF is requesting a one year extension of the MATS compliance requirements for Units 4 and 5.”
The application added: “Despite several years of monitoring for confirmation of existing controls, a change in mercury emissions was only recently observed, and was beyond reasonable control. DEF first learned of an individual occurrence of a spike in mercury emissions from Unit 5 in July 2014. The mercury emissions returned to within the normal range of the previous two years, but September resulted in a second peak. DEF commissioned a study to identify the cause and options for control. As described further in subsequent sections, an extension of the MATS compliance date for Units 4 and 5 is necessary to provide sufficient time to fully implement controls to mitigate re-emission of mercury.”
The utility wrote: “To further investigate and mitigate mercury re-emissions, DEF is expediting the installation of a re-emissions chemical additive system. This system in being used successfully on several other units within the Duke Energy fleet. Operating conditions and FGD chemistry vary from unit to unit; therefore, testing on Units 4 and 5 is necessary to determine whether this chemical will be effective. Initially, DEF will install a temporary system to conduct this testing and investigate appropriate chemical injection rates. DEF expects to install the system in the February/March 2015 timeframe. In parallel, DEF must design and install a permanent system, followed by testing and tuning of control logic. The permanent system must utilize a mercury [continuous emissions monitor] as an input to the control logic. The signal from this CEM will be used for determining the chemical injection rates. By contrast, the temporary system will rely on feedback from the existing sorbent traps, which provide mercury emissions results with a 10-14 day lag time. The mercury CEM and its associated equipment have the longest lead times for implementation.”