Alloys turn up the heat with less boiler corrosion

The high-efficiency power plant of the 21st century may still be on the drawing boards, but the new high-strength, corrosion resistant alloys that will make these power plants possible are about to enter the “real life” testing stage.

The Department of Energy (DOE) will provide $700,000 of a $1.9 million contract for a five-year testing program to McDermott Technology Inc., Alliance, Ohio, Babcock & Wilcox, Consol of Library, Pa., the Ohio Coal Development Office, DOE`s Oak Ridge National Laboratory, and Ohio Edison to test 10 of the most promising of these alloys in a coal-fired boiler at Ohio Edison`s Niles Power Station (246 MW).

The results will provide key information for use in designing higher-efficiency, super-critical coal-fired power plants. Super-critical plants create steam under high pressures that is much hotter than the steam produced by a typical coal-burning power plant. Boosting steam temperatures raises a power plant`s operating efficiency, which makes the plant more economical to operate, generates lower cost electricity, and produces fewer greenhouse gas emissions.

At higher temperatures, however, the metals used in a boiler`s steam tubes are more prone to corrosion caused by hot coal ash depositing on the tubes.

At the Niles Power Station, the alloys will be positioned in specially designed, high-temperature test rigs between tube bundles called the superheater and reheater that increase steam temperature. For up to five years, the alloys will be subjected to temperatures of 1,050 F to 1,150 F, well above steam temperatures of today`s standard boilers, typically ranging from 950 F to 1,000 F. At the end of one, three and five years, each rig will be removed and evaluated for corrosion.

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