Duke Energy Florida (DEF) applied Nov. 23 at the Florida Department of Environmental Protection for air permit changes that cover the shutdown of the steam boilers at the Suwannee River plant, leaving this facility as only a peaker.
The Suwannee River Power Plant (SRPP) is located in Live Oak, Suwannee County, Florida. It is a nominal 345-MW facility comprised of three fossil fuel-fired steam boilers (Units 1, 2, and 3) and three Turbo Power and Marine Systems Twin-Pac simple cycle combustion turbine (SCCT) peaking units (Units CTP1, CTP2, and CTP3).
The three Twin-Pac SCCT peakers are each comprised of two identical dual-fuel (i.e., natural gas and No. 2 fuel oil) aeroderivative combustion turbines (P1A through P3B) and one common electrical generator for a total of six SCCTs and three electrical generators.
Said the Nov. 23 application: “DEF plans to permanently cease operation of the three steam boilers. As a result, DEF anticipates the need to increase annual operating hours for the three peaking units to replace power previously generated by the steam boilers as well as to provide voltage stabilization for the electric grid.
“Specific Condition B.1 of Title V Air Operation Permit No. 1210003-010-AV limits operation of the SCCTs to no more than 1,500 hours per year (hr/yr) for each of the six SCCTs. As required by Condition B.1, each SCCT may operate up to 1,500 hr/yr on either natural gas or No. 2 fuel oil, or any combination of fuels as long as the total annual operating hours do not exceed 1,500 hr/yr for each SCCT.
“To accommodate an increase in authorized operating hours for the SRPP peaking units, DEF requests a NOx emission cap of 633 tons per year (tpy) for the six SCCT peaking units. Based on NOx emission factors of 0.190 lb/106 Btu (for natural gas) and 0.215 lb/106 Btu (for fuel oil), the requested NOx emission cap will allow each SCCT to operate for up to 3,012 hr/yr on natural gas, or up to 1,313 hr/yr on natural gas and 1,500 hr/yr on No.2 fuel oil, or any combination of fuels as long as the NOx emission cap is not exceeded and the total annual operating hours for each SCCT do not exceed do not exceed 1,500 hr/yr when firing No. 2 fuel oil.
“DEF is not requesting any changes to current Title V permit requirements with respect to No. 2 fuel oil firing. In addition, there will be no changes to currently authorized maximum hourly heat input and fuel consumption rates, or fuel heating values and sulfur contents.”
Duke Energy Florida had filed April 1 with the Florida Public Service Commission a Ten-Year Site Plan that indicated the shutdown plans for the Suwannee steam units. These ten year plans, which are something like a truncated integrated resource plan, are filed annually with the commission by Florida utilities.
The promulgation of the Mercury and Air Toxics Standards (MATS) by the U.S. EPA in 2012 presents new air requirements for the DEF units at Anclote, Suwannee River and Crystal River. DEF said two steam units at Anclote and the three steam units at Suwannee River have switched to natural-gas-only operations in order to comply with the MATS rule. Residual Fuel Oil is no longer used.
DEF said in the April 1 filing that it continued to look ahead to the projected retirements of several of the older units in the fleet, particularly combustion turbines at Higgins, Avon Park, Turner and Rio Pinar as well as the three steam units at Suwannee River. Turner Unit P3 was retired July 2015. The Rio Pinar and Turner Units P1, P2 and P4 continued to show anticipated retirement dates in 2016. Suwannee River steam units 1, 2 and 3 were projected to retire in November 2016. Continued operations of the peaking units at Higgins and Avon Park are planned until the year 2020. There are many factors which may impact these retirements including environmental regulations and permitting, the unit’s age and maintenance requirements, local operational needs, their relatively small capacity size and system requirement needs.