Combined cycle - Wikipedia, the free encyclopedia

An Integrated Gasification Combined Cycle, or IGCC, is a power plant using synthetic gas (syngas). Below is a schematic flow diagram of an IGCC plant:

The gasification process can produce syngas from high-sulfur coal, heavy petroleum residues and biomass.

The plant is called "integrated" because its syngas is produced in a gasification unit in the plant which has been optimized for the plant's combined cycle. The gasification process produces heat, and this is reclaimed by steam "waste heat boilers". The steam is utilized in steam turbines.

There are currently (2007) only two IGCC plants generating power in the U.S.; however, several new IGCC plants a

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The main problem for IGCC is its extremely high capital cost, upwards of $3,593/kW^[1]. Official US government figures give more optimistic estimates ^[2] of $1491/kw installed capacity (2005 dollars) v $1290 for a conventional clean coal facility.This is about 20% greater cost than a conventional pulverized coal plant, but the U.S. Department of Energy and many states offer subsidies for clean coal technology projects that could help to bridge the cost gap.

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However, the per megawatt-hour cost of an IGCC plant vs. a pulverized coal plant coming online in 2010 would be $56 vs $52. And IGCC becomes even more attractive when you include the costs of carbon capture and sequestration, IGCC becoming $79 per megawatt-hour vs. $95 per megawatt-hour for pulverized coal. ^[3]

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The power generation industry has yet to show that IGCC is reliable. Of five demonstration facilities, none had availabilities comparable to conventional CCGTs or coal-fired power plants. Wabash River was down repeatedly for long stretches due to gasifier problems, and the gasifier problems have not been remedied -- subsequent projects, such as Excelsior's Mesaba Project, have a third gasifier and train built in. However, the past year has seen Wabash River running reliably, with availability comparable to or better than other technologies.

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With carbon capture, the cost of electricity from an IGCC plant would increase approximately 30%. For a natural gas CC, the increase is approximately 33%. For a pulverized coal plant, the increase is approximately 68%. This potential for less expensive carbon capture makes IGCC an attractive choice for keeping low cost coal an available fuel source in a carbon constrained world.

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