Edwardsport IGCC plant begins commercial operation

Duke Energy's Edwardsport Generating Station has begun commercial operation recently. Located in Knox County, Ind., near Vincennes, the 618MW coal gasification plant uses advanced technology to gasify coal, strip out pollutants, and then burn that cleaner gas to produce electricity. 

The technology substantially reduces the environmental impact of burning coal to produce electric power making the plant one of the cleanest coal-fired power generating facilities.

The two GE 7F syngas turbines recently shipped to Duke Energy’s Edwardsport IGCC plant are expected to operate on cleaner burning syngas fuel produced from coal. 

The 7Fsyngas turbine has an ISO rating of 232 MW, operating with oxygen-blown, medium Btu syngas fuel. This unit’s increased power and efficiency, due in part to increased mass flow, delivers a reduced cost of electricity.

There are several physical differences between the 7F syngas turbine and existing syngas and natural gas turbines. The compressor enables higher flow/pressure ratio capability, which improves output and efficiency across the base load operating range. This turbine also includes an optimized hot gas path (HGP) for use with syngas fuels. Aerodynamic improvements to the turbine accommodate the increased mass flow that occurs with syngas. This includes an increased area in Stage 3 to mitigate high aerodynamic losses that would limit gas turbine output and efficiency.

The 7F syngas turbine also uses 7FA HGP materials with corrosion resistance in syngas operating environments. It also incorporates improved case and rotor features, to allow for higher torque and higher temperatures and improved output across the base load operating range. 

The new syngas turbine uses GE’s syngas combustion system, with turndown from full load to 50 percent load. Since this is a diffusion system where the reaction occurs in the combustion zone with an equivalence ratio equal to one, it provides a flame that is stable and robust to blow-out and combustion dynamics.

The Edwardsport project began in 2008 and the company completed the necessary steps to be declared commercial on June 7. It will provide the following environmental advantages:

* Produce 10 times as much power as the former plant at Edwardsport, yet with about 70 percent fewer emissions of sulfur dioxide, nitrogen oxide and particulates combined.

* Use excess steam that would normally be wasted to power a second turbine and increase plant efficiency and output.

* Reduce carbon dioxide emissions per megawatt-hour by nearly half compared to the plant it replaces.

* Generate marketable byproducts. The plant will produce sulfur and slag for agricultural and construction materials. Any revenues from marketable byproducts will go to customers.

* Use less water than a conventional coal-fired plant.

As the company testified before state regulators, this is the first time the technology has been used on this scale, so the plant is expected to build up to its long-term level of availability over the next 15 months. It will provide Indiana customers with power for decades.

Highlighting the fact that the average age of coal-fired plants on Indiana system is 45 years and this facility is key to modernizing the system and filling the gap left by plant retirements, Duke Energy Indiana President Doug Esamann said, "Coal has powered Indiana for more than a century. But today's air quality standards require us to use that fuel in a cleaner, more efficient way. Edwardsport turns coal into a cleaner-burning fuel and enables us to continue using an abundant local resource. It replaces about 500 MW of older coal-fired generation that we recently retired or expect to retire soon due to new EPA regulations."