Ultra-Supercritical Steam Corrosion Page: 2 of 6
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Vision 21 initiative has the goal of 50% efficiency for coal-based power generation. The Clean Coal
Power initiative has goals of a 675 C (1247 F) steam temperature by 2010 (45-50% efficiency) and
760 C (1400 F) by 2020 (50-60% efficiency). Currently, most supercritical boilers have steam
temperatures of 565 C (1049 F); a few have steam temperatures of 593 C (1099 F) [Kishimoto et al.
The Advanced Research (AR) program has two efforts in ultra-supercritical (USC) steam-one on USC
boilers and one on USC turbines. The overall steam temperature and pressure goal is 760 C (1400 F)
and 38.5 MPa (5586 psi) by 2020. There are intermediate goals for demonstrating the use of materials
with steam temperatures of 650 C (1202 F) by 2010 and 760 C (1400 F) by 2015 [Dogan and Wright
2003]. The Albany Research Center (ARC) is taking part in the steamside oxidation research in the
USC turbine effort. A major part of the USC turbine effort is the selection or development of candidate
alloys suitable for use in the USC turbine. Until candidate alloys are selected, initial tests at ARC will
be done using the six candidates from the USC boiler project that have already been identified. These
are ferritic alloy SAVE 12, austenitic alloy Super 304H, the high Cr-high Ni alloy HR6W, and the
nickel-base superalloys Inconel 617, Haynes 230, and Inconel 740. Each of these alloys has very high
strength for its alloy type. Three types of oxidation experiments are planned: cyclic oxidation in air plus
steam at atmospheric pressure, thermogravimetric analysis (TGA) in steam at atmospheric pressure, and
exposure tests in supercritical steam up to 650 C (1202 F) and 34.5 MPa (5000 psi). This temperature
and pressure correspond to the intermediate USC goal for demonstration use by 2010.
An important question to be answered is the role of pressure on steamside oxidation. It is important in
two aspects. The most important one comes from that fact that most of the efficiency gains result from
increased temperature, not pressure [Viswanathan and Bakker 2001]. As a consequence, material
requirements, in terms of high temperature strength and steamside oxidation, could lead to the use of
lower pressures (than the goalof 38.5 MPa) to make USC turbines economical, and yet still beneficial in
terms of efficiency increases. The other aspect is that testing of alloys at higher temperatures and
pressures than 650 C (1202 F) and 34.5 MPa (5000 psi) becomes very expensive. If the role of pressure
on steamside oxidation was understood better, then less expensive tests at higher temperature and lower
pressures should provide the necessary information at lower cost. The planned atmospheric pressure
tests, combined with supercritical exposures at 13.8, 20.7, 24.6, and 34.5 MPa (2000, 3000, 4000, and
5000 psi), are designed to determine the effect of pressure on the oxidation process in supercritical
Initial oxidation experiments will be done on the six alloys selected as candidates for the USC boiler
effort. The primary aim of these initial experiments is to ensure that the three types of experiments are
working properly and will be ready when the USC turbine alloys are selected. However, these results
should also benefit the USC boiler research and overall USC goals. The six alloys are ferritic alloy
SAVE12, austenitic alloy Super 304H, the high Cr-high Ni alloy HR6W, and the nickel-base superalloys
Inconel 617, Haynes 230, and Inconel 740.
1 Efficiency, as used here, is based on higher heating value (HHV), or gross calorific value.
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Holcomb, G. R.; Alman, D. E.; Bullard, S. B.; Covino, B. S., Jr.; Cramer, S. D. & Ziomek-Moroz, M. Ultra-Supercritical Steam Corrosion, article, April 22, 2003; Pittsburgh, Pennsylvania. (digital.library.unt.edu/ark:/67531/metadc787689/m1/2/: accessed November 12, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.