Tuesday, March 11, 2014

The Ultra-Supercritical Coal-Fired Turk

AEP's Turk is one of the most efficient, least polluting coal-fired power plants on the planet.
AEP's Turk is one of the most efficient, least polluting coal-fired power plants on the planet.

AEP's ultra-supercritical coal-fired Turk power plant is a great technological leap forward unlikely to ever be repeated again in the United States.  The Turk project was announced in August 2006 but didn't go online until seven years later.  AEP succeeded in bringing online the most efficient coal-fired commercial power plant ever built.

The 600 MW Turk Power Plant is situated in Hempstead County, in the southwestern corner of Arkansas, where it employs 109 people on a total payroll of $9 million and pumps $6 million in school and county property tax revenues every year, according to AEP. Through its subsidiary the Southwestern Electric Power Co., or SWEPCO, which operates the facility, AEP invested $1.3 billion of the $1.8 billion required to build the plant and the company now owns 73 percent of its output. The remaining ownership is divided between the Arkansas Electric Cooperative Corp., the East Texas Electric Cooperative, and the Oklahoma Municipal Power Authority.

The attribute that makes Turk unique among power plants-that gives cause to append the word "ultra" to the preexisting and more familiar "supercritical"-is that it works just like a supercritical power plant, only better. As an ultra-supercritical coal-fired power plant, Turk operates at extraordinarily high pressures and temperatures, well above typical supercritical pressures of around 4,500 psi and hotter than 1050 degrees Fahrenheit.

As you increase temperature you increase your efficiencies. By working at such a high temperature and pressure, Turk achieves the highest efficiencies around in coal power generation today; according to AEP, between 39 and 40 percent of the thermal energy available in the fuel comes out as electric power. This level of efficiency in extracting energy from coal allows Turk to use less of the stuff to produce the same amount of power. Less coal burned means less emissions of sulfur dioxide, nitrogen oxide, mercury, carbon dioxide and particulate matter. It also means fewer waste products and less fly ash, and decreased need for the commodities used in environmental control activities, like activated carbon and ammonia. The reduction in pollutants is combined with the latest emission-control technologies, like catalytic reduction systems, dry flue gas desulfurization, baghouse technology to combat particulate releases and activated carbon injection to reduce Hg emissions. The end result is one of the most efficient, least polluting coal-fired power plants on the planet.

Achieving super-high temperatures and pressures wasn't as easy as just dialing up the heat. Special materials had to be tested to withstand the pressure and temperature of an ultra-supercritical power plant. For use in the facility materials need to have high creep rupture strength, resistance against embrittlement, and low oxidation growth in addition to ease of manufacture and availability. High chrome, creep strength enhanced ferritic steels (CSEF), and nickel based alloys meet these needs.

Unfortunately with the new environmental rules for new generating facilities, the proposed CO2 limits are probably going to prevent another such plant from being built.
"This could very well be one of the last conventional coal burning facilities built in the country. (Power Engineering, 6/12/2013)

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