Combustion
Repowering Duke Power's Dan River Station
Unit 3 with APFBC
FBC Repower APFBC AES Greenidge APFBC Dan River FBC, APFBC Four Corners CHIPPS H.F. Lee
Products Summary Sheldon Summary APFBC Sheldon GFBCC Sheldon APFBC L.V. Sutton
Contents:
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APFBC Repowering Project Summary
Duke Power's Dan River station is located near Eden, North Carolina. The photo is a view of the station looking toward the northeast with the Dan River in the foreground. This river provides cooling for the plant. The proposed APFBC repowering would be placed in the clear level area to the west of the powerhouse, left in the photo, just past the transformers and switchyard at the front of this photo.
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Advanced circulating pressurized fluidized-bed combustion combined cycle systems (APFBC) are systems with jetting-bed pressurized fluidized-bed (PFB) carbonizer/
gasifier and circulating PFBC combustor. The PFB carbonizer and PFBC both operate at elevated pressures (10 to 30 times atmospheric pressure) to provide syngas for a operating a gas turbine topping combustor giving high cycle energy efficiency. The remaining char from the PFB carbonizer is burned in the pressurized PFBC. The combustion gas from the PFB also feeds thermal energy to the gas turbine topping combustor. This provides combined cycle plant efficiency on coal by providing the opportunity to generate electricity using both high-efficiency gas turbines and steam.
APFBC systems are discussed in detail on other portions of this web site. Click here for a summary overview on APFBC repowering.
APFBC is under development by industry and the DOE. A commercial demonstration of APFBC technology is underway at DOE's Power Systems Development Facility (PSDF) in Wilsonville, Alabama. If that demonstration occurs successfully, APFBC should soon be ready for commercial orders. A number of electric companies are looking at the technology to see whether APFBC repowering makes sense for them.
Duke Power volunteered their evaluation support for the study, getting no government funding.
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Key Features
Foster Wheeler supplies the APFBC island equipment, Siemens Westinghouse the high-temperature 1400ºF ceramic syngas and vitiated air filters. In this concept, a single Siemens Westinghouse W501F gas turbine and topping combustor, modified for APFBC service, adds output to the plant. In this concept, the existing Dan River station Unit 3 is repowered with one W501F and APFBC train. With this scheme, each of the steam turbines is retained as the steam bottoming cycle for its respective train. Once the Unit 3 APFBC system is put in place and tested, the existing Unit 3 boiler is no longer needed and can be demolished. The hot exhaust of the W501F gas turbine includes a heat recovery unit (HRU), used as economizer surface to recover its exhaust heat. Using the gas turbine exhaust heat this way increases the energy efficiency. After economizing, the hot water from the HRU is sent to the PFBC's in-bed tubes to generate superheat and reheat steam.
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There are three steam units at the Dan River site, all coal-fired. Only Unit 3 is considered for APFBC repowering in this study. The larger Unit 3, a 150,000 kW output, 1800 psig/1000ºF/1000ºF reheat unit, is located toward the southwest adjacent to the power house wall visible on the left in the photo. There is adequate space to add APFBC repowering equipment in the area on the left.
APFBC increases the amount of electric output from the plant. The efficient new equipment continues the use of coal there, but lowers electricity production costs. The method significantly reduces the amount of wasted energy, so more electricity is produced from each ton of coal, with much less pollution. These studies show that APFBC has attractive characteristics, and that it appears easily customized to match the steam demands of the existing plant equipment. This is important compared to many other ways of repowering a plant, since it means that with APFBC, more of the existing equipment at the plant can be re-used, keeping costs low.
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Site Layout
The APFBC equipment would fit nicely in the level area to the west of the existing power house. This would place the APFBC equipment immediately adjacent to Unit 3, with convenient access to the existing steam turbine and coal handling. Limestone handling would have to be added. Enlarge the sketch below to see where the equipment would fit on the site.
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Performance
Repowering Unit 3 with APFBC would about double its output. The energy efficiency of these units would improve from 36.4 percent on an HHV basis to 43.2 percent with the proposed APFBC repowering upgrades. The resulting fuel savings would result in a significant reduction in production costs.
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Environmental Characteristics
APFBC is an exceptionally clean technology, one of the principal benefits of an APFBC repowering project. Enlarge the image below to see the benefits to the station.
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Cost
The cost range estimate to implement the repowering of Unit 3 is shown in the illustration below.
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