Duke Energy nears air permit for 1,640-MW Citrus Combined Cycle Project

The Florida Department of Environmental Protection is out for comment on a draft air construction permit covering the 1,640-MW Citrus Combined Cycle Project (CCCP) of Duke Energy Florida.

The gas-fired project would be built next to the utility’s existing Crystal River power plant, and will in part make up for the shutdown later this decade of Crystal River’s two oldest coal units (Units 1 and 2). The project of this Duke Energy (NYSE: DUK) subsidiary was recently approved by the Florida Public Service Commission. The department issued the draft construction permit on Nov. 13.

The CCCP will consist of two power blocks designated as CCCP Units 1 and 2. Each power block at Citrus will consist of:

  • two natural gas-fueled nominal 270-MW Mitsubishi Power Systems (MPS) 501GAC combustion turbine-electric generators (CTGs) with optional inlet chillers;
  • two heat recovery steam generators (HRSGs) equipped with natural gas-fueled duct burners and selective catalytic reduction (SCR) reactors;
  • two 180-foot exhaust stacks; and
  • a nominal 280 MW steam turbine electric generator (STG).

Ancillary equipment includes: an auxiliary boiler; two natural gas-fired fuel gas dew point heaters; two ultra-low sulfur diesel (ULSD) fueled emergency generators; one ULSD fueled emergency firewater pump engine; two mechanical draft cooling towers; and two CTG inlet chiller cooling towers.

Each power block will operate as a two-on-one (i.e. two CTG/HRSG sets and one STG). The turbine exhaust gas from each CTG will produce additional steam in each HRSG. The energy contained in the turbine exhaust gas will at times be further augmented by burning gas within the HRSGs duct burners. The steam from the two HRSGs (per block) will, in-turn, drive a single separate STG (per block), thus producing additional electrical power.

The MPS 501GAC combustion turbine generator is expected to achieve nearly 59% thermal efficiency in combined cycle operation on the basis of the lower heating value (LHV) of natural gas (about 56% based on higher heating value, HHV). Duct firing is useful during periods of high-energy demand much like a small but efficient peaking unit. When used, the gas-fired duct burners in the HRSG provide additional heat to the turbine exhaust gas. This increases steam production and steam-generated electricity.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.