Florida Power & Light applied in December at the Florida Department of Environmental Protection for an air construction permit covering the replacement of components in the gas turbines at Fort Myers plant Unit 2, allowing 5% uprates of those turbines.
The application, prepared by consultant Golder Associates, noted that Fort Myers Unit 2’s six gas turbines are permitted to fire only natural gas. The turbines are called Units 2A through Unit 2F, with each rated at a total of 250 MW. In describing these six turbines and how they are configured, the application said: “6-on-1 combined cycle system consisting of six nominal 170 MW GE 7FA.04 combustion turbine-electrical generator sets with unfired HRSG that produces sufficient steam to generate additional 80 MW.”
There are other turbines at the plant outside of Unit 2 that are not covered by this permitting. The GenerationHub database shows the plant’s total capacity as 2,828 MW.
The current design heat input rates for the six turbines are 1,535 million British thermal units per hour (MMBtu/hr). There will be no change in the type of permitted fuels as a result of the project. The design heat input rate for natural gas firing will increase by 29 MMBtu/hr (2%) based on General Electric data on 7FA.04 turbines at 75°F ambient temperature.
“The purpose of the project is to improve the performance of the GE Model MS7241 turbines with 7FA.04 components,” said the application. “The components being replaced are typically those requiring routine replacement due to normal operation. However, replacing the 7FA.03 components with 7FA.04 components results in higher efficiency and provides approximately a 5 percent increase in output power per turbine with an approximate two percent decrease in heat rate (heat input/output power) per turbine (1-percent for combined-cycle operation).”
The improved 7FA.04 model turbines will guarantee the same concentration-base emissions limits for NOx, carbon monoxide (CO) and volatile organic compounds (VOC). Based on GE performance data for the 7FA.03 and 7FA.04, the potential hourly mass emission rate of NOx will theoretically increase from 55.3 to 56.5 pound per hour (lb/hr) (at 75°F). However, the increased rates are less than the current permitted emissions rate of 65 lb/hr.
Fort Myers Unit 2 consists of six gas turbine electrical generator sets, which include GE Model MS7241 turbines/generators, heat recovery steam generators, and a steam electric generator. The proposed project will replace component parts normally associated with maintenance outages for the GE MS7241, 7FA.03 turbine with 7FA.04 components, which offer greater output and greater efficiency without sacrificing reliability, availability, or operational flexibility.
The 7FA.04 components will increase the output power by approximately 5% (base load at 75°F). As a result of the greater output, mass emission rates of all criteria pollutants will decrease on a per MW-hr basis The project will include installation of new hot gas path components, new combustion liners and flow sleeves, and new control software to increase firing temperature.
The advanced gas path of 7FA.04 uses less air for cooling the parts, the application noted. As a result, more air is available for combustion and power generation. The turbines will remain equipped with the DLN 2.6 combustion system, which is GE’s latest evolution of Dry Low-NOx combustion technology.