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Contents:

• Summary

• Key Features of Greenidge APFBC Repowering Project

• Operating Conditions

• APFBC Repowered AES Greenidge Unit 4 Process Decisions

• Gas Turbine

• Environmental and Licensing

Click on picture to enlarge

Summary
Units 3 and 4 are the last steam turbines installed at AES Greenidge steam power plant.  These units are the focus of this DOE APFBC repowering evaluation.  Information relating to the station and studies includes the following:

• Space is available to the west, and in the power house.

• Greenidge Unit 4, on left, is the main focus.  It is a 106.3 MW unit built in 1953.

• It has a 665,000 pph, 1450 psig / 1000ºF / 1000ºF reheat boiler.

• The present station heat rate is excellent, 9,676 Btu/kWh HHV (35.3% net plant efficiency).  No scrubber and deep-lake circulating water for condenser cooling.

• It is one of the earliest dispatched coal units in New York, with a 60.0% average annual capacity factor.

• Unit 3, a 55.0 MW, 850 psig / 900ºF 1950 non-reheat unit will be considered for use if added output is attractive.

• Results of the APFBC repowering are reported in Parsons Infrastructure & Technology Group Report No. EJ-9703.

Advanced circulating pressurized fluidized-bed combustion combined cycle (APFBC) technology is a coal-fired technology now under test in large-scale demonstrations, which will be ready for commercial repowering installations around year 2005.  This paper describes a conceptual design evaluation effort that assessed the merits of APFBC repowering the AES Greenidge electric generation plant.  This steam power plant is located near Dresden, New York. The focus of the study is Unit 4 at the station.  Unit 4 is a 108,000 kWe reheat unit that sits on Seneca Lake, one of New York's Finger Lakes.

Earlier APFBC repowering concept evaluations show that APFBC has some important advantages for the power generating company owner.  Output is nearly doubled, environmental performance is excellent, and energy efficiency increases from 4 to 10 percentage points.

For AES Greenidge Unit 4, instead of the large frame gas turbine used in earlier studies, a modified aeroderivative gas turbine, the Rolls-Royce Industrial Trent, is evaluated.  This gas turbine has a significantly higher overall pressure ratio compared to the frame type machines evaluated in the previous studies.  The concept evaluation here considered a 2 x Trent configuration for the repowering of Greenidge Unit 4.

The existing AES Greenidge Unit 4 steam turbine has high flow in its low-pressure section.  This proves a particular challenge for an APFBC repowering, which operates best with most of the feedwater heaters out of service for highest energy efficiency.  However, the existing Unit 4 has a rather high steam turbine exhaust velocity, about 1,264 feet per second, in the exhaust hood in normal operations, so taking feedwater heaters out of service has the undesirable consequence of further increasing exhaust velocity.  Even with significant steam turbine back-end flow limitations, APFBC repowering boosts Unit 4 output from 106,310 kW to 206,300 kW, and the unit is expected to move from its present 34.6 percent HHV net plant energy efficiency to operate at 39.8 percent HHV energy efficiency with APFBC.  Environmental performance is excellent.   Different APFBC integration options can overcome the steam turbine limitations, and produce even higher energy efficiency.  This web site discusses the actions taken to maintain acceptable exhaust conditions.  Different APFBC integration options can overcome the steam turbine limitations and produce even higher energy efficiency.

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Key Features of AES Greenidge APFBC Repowering Project

The photo at the beginning of this web page shows a view of the power plant facing northeast.  Turbine generator Unit 4, a 108 MWe output reheat unit at the left in the photo, is supplied by Boiler No. 6, which uses the stack to the left.  With APFBC repowering, Boiler No. 6 would be replaced by the APFBC equipment, but the turbine/generator and other plant equipment would be retained.

AES Greenidge  is interested in APFBC repowering for the following reasons:

• APFBC repowering affords the opportunity to increase generation capacity
  and improve heat rate.

• In a competitive business environment, low price wins.

• Coal remains an important fuel for AES Greenidge.

• APFBC is a clean technology, has good cycle efficiency, and has the technology test programs in place to prove its feasibility.

• Should gas prices increase above projections, coal projects could become more favorable.

AES Greenidge wants to understand this technology better to determine the feasibility of APFBC as a possible next coal-fired unit generation expansion option.

While the concept assessment is still underway, some preliminary observations can be made about possible locations for the APFBC equipment at the site:

• The APFBC equipment could be placed at the west of the existing equipment, adjacent to Unit 4, to the left of the power house in the photo.

• There is adequate level space to the west, but several small structures would need to be relocated.

• The high-energy steam pipe run lengths would be acceptable.

• Coal delivery could make use of much of the existing coal delivery system.

• The length of transmission wire to get to the switchyard would be acceptable, and the yard has adequate capacity to distribute the added generation to the high lines.

• The west end of the coal yard might be used for limestone delivery.

A west-end arrangement is tentatively chosen for APFBC.

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Operating Conditions

The operating conditions for APFBC repowering Greenidge Unit 4 are as follows:

• Carbonizer temperature: 1700ºF.

• Fuel gas temperature to filters: 1430ºF.

• Circulating PFBC bed temperature: 1600ºF.

• Vitiated air temperature to filters: 1450ºF.

• Heat recovery steam generator stack temperature: 280ºF.

The estimated performance of the AES Greenidge Unit 4 (Case 2, Unit 3 and Unit 4) repowered in the seven configurations evaluated with APFBC is listed below.  Case 1 was selected as the primary evaluation focus.