Combustion
Repowering Nebraska Public Power District's Sheldon Station with APFBC Technology
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:
Other Combustion Systems Repowering Study Links:
A related study is underway that would repower Sheldon Unit 1 and Unit 2 with gasification fluidized-bed combined cycle technology (GFBCC). CLICK HERE
to find out more about repowering the Sheldon station with GFBCC instead.
APFBC Repowering Project Summary
Click on picture to enlarge
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 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.
The host site for this repowering concept evaluation is Nebraska Public Power District’s Sheldon steam generating station. The Sheldon station is a coal-fired electric generating station located near Hallam, Nebraska, about 25 miles south of Lincoln. The plant was constructed between 1958 and 1963 as an experimental nuclear power plant for the Atomic Energy Commission. After the Commission (today known as the Nuclear Regulatory Commission) acquired the information it needed, the nuclear portion of the facility was decommissioned and the equipment and parts were sent to other nuclear plants or disposal sites. What could not be moved was sealed and buried in large vaults beneath the earth's surface at the plant.
Today, Sheldon station's two boilers can generate 225,000 kilowatts of electricity. There are two coal-fired steam units at this site:
- Unit 1, commissioned in 1961, is a 108,800 kW output reheat unit.
- Unit 2, commissioned in 1965, is a 119,000 kW output reheat unit.
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 is successful, APFBC should be ready for commercial orders soon. A number of electric companies are looking at the technology to see whether APFBC repowering makes sense for them.
The Nebraska Public Power District volunteered its evaluation support for the study, getting no government funding.
Back to Contents Back to TOP
Key Features
In this concept, a single GE PG7121EA gas turbine and topping combustor, modified for APFBC service, add output to the plant. The existing Sheldon station Unit 1 is repowered with one PG7121EA and APFBC train. A second, nearly identical train repowers Unit 2. With this scheme, each of the steam turbines is retained as the steam bottoming cycle for its respective train. Once the Unit 1 APFBC system is put in place and tested, the existing Unit 1 boiler is no longer needed and can be demolished. The hot exhaust of the PG7121EA 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.
This concept uses moderate temperature syngas conditions to the syngas filter and topping combustor, and 1000oF vitiated air conditions to the vitiated air filters and topping combustor.
The Unit 2 repowering is similar. When the Unit 2 APFBC is put in place, the Unit 2 boiler is no longer needed and can be demolished.
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.
Back to Contents Back to TOP
Site Layout
Click on picture to enlarge
Back to Contents Back to TOP
Performance
Click on picture to enlarge
Station output increases about 80 percent when APFBC is added. This occurs while significantly improving the energy efficiency of the station, reducing the amount of coal needed per kilowatt generated by about 17 percent. This means that the fuel cost for generation is reduced, significantly reducing production costs. The illustration below shows the expected improvements.
Back to Contents Back to TOP
Environmental Characteristics
Click on picture to enlarge
The environmental performance of the two Sheldon station units when repowered with APFBC is excellent, one of the more attractive features of this technology as a plant repowering option. The illustration below shows the significant amount of pollution reduction that would occur were Unit 2 repowered with APFBC.
Back to Contents Back to TOP
Cost
This study did not assess the cost for APFBC repowering. These costs are well-established in other studies, ranging from about $800 to $1,100 per combined kW. Return to the CONTENTS at the top of this web page, and link to one of the related APFBC repowering evaluation studies at other plant sites for more cost detail.
|
ABOUT NETL
Deepwater Technology
