Duke Energy Florida applied Jan. 13 at the Florida Department of Environmental Protection for a one-year extension, to April 2016, of the federal Mercury and Air Toxics Standards (MATS) compliance deadline for the coal-fired Units 4 and 5 of the Crystal River power plant.
The extension application, written by Trinity Consultants, is part of a revision of the Title V Air Operation Permit for the plant, which includes four coal units and a retired nuclear facility. The Crystal River facility consists of the South Plant which includes two fossil fuel-fired electric utility steam generators (FFSG) (Units 1 and 2) that began operation in the 1960s, and the North Plant which includes two additional fossil fuel-fired electric utility steam generators (Units 4 and 5) that began operation in the 1980s. All four units are subject to EPA’s MATS rule.
“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,” said the application. “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.”
Units 4 and 5 each consist of a pulverized coal, dry bottom, wall-fired boiler rated at 760 MW. 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. Air pollution control equipment on Units 4 and 5 includes: low-NOX burners; selective catalytic reduction (SCR) systems; AMM systems; an electrostatic precipitator (ESP); and relatively new flue gas desulfurization (FGD) systems.
“Despite several years of monitoring for confirmation of existing controls, a change in mercury emissions was only recently observed, and was beyond reasonable control,” said the application. “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 added: “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.
“Due to recent and unexpected increases in mercury emissions, DEF is proposing to install a Nalco mercury re-emission control system on Units 4 and 5 for use with the MerControl 8034 Plus chemical. The MerControl 8034 technology is a water-soluble additive used to precipitate oxidized mercury in wet FGD scrubbers, thus reducing the potential for re-emission and lowering the overall mercury emissions at the stack. … The system will be comprised of a single fiberglass reinforced plastic (FRP) chemical storage tank to serve both Units 4 and 5. Two pump skids (one for each unit) will take suction from the storage tank. Each skid will contain two dosing pumps for normal use and one system charge pump for higher volume additions of the chemical. The pumps will be controlled by a controller loaded with a Nalco proprietary control algorithm. The algorithm takes input from several unit parameters to determine the chemical injection rate. In addition to the permanent system, a temporary system will be leased from Nalco and installed in the first quarter of 2015. While this system will utilize more primitive controls, it will allow for early development of control algorithms, as well as for mitigation of mercury re-emissions prior to implementation of the permanent system.”